CNR-INFM Regional Laboratory
SUPERMAT
Superconducting new materials and multilayers:
nanostructure, transport and magnetic properties
Scientific Report 2005-2008
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Scientific Report 2005-2008
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SUPERMAT is one of the Regional Laboratories of the Institute for the Physics of
Matter (INFM) which is part of the National Research Council (CNR). SUPERMAT
was constituted by the INFM Scientific Council in the April 2003.
The “SUPERMAT” Laboratory was born from the research activities developed
since many years at the INFM Research Unit of Salerno which represented a pole in
the field of superconductivity, both from an experimental and a theoretical point of
view.
After the merging of the INFM in the CNR, the introduction of the Commesse
(“Interplay of superconductivity and magnetism” and “Transport properties in
superconducting materials”) gave a natural arrangement of the SuperMat scientific
activities, leading to a more focalized research activity of SuperMat: the associate
accademic staff was reduced in number while the SuperMat personnel was reinforced
by the recruitment of 7 researchers. Since 2006, a consultative board is active
(SuperMat Internal Committee) supporting the Director in the scientific address of the
research activities.
The activities are concentrated on the synthesis of materials, the analysis of their
structural, morphological, transport and magnetic properties, as well as on the
fabrication and investigation of hetero-structures. In the last five years, the SuperMat
has worked out a policy towards the acquisition of strategic equipments that would
better position it within the related research international framework. Through a series
of successful projects, the SuperMat has equipped the laboratories with dedicated
instrumentations (floating zone single crystal furnace, sputtering, high resolution
diffractometer, scanning electron microscope equipped with many detectors, scanning
tunnel microscope, atomic and magnetic force microscopes, vibrating sample
magnetometers, etc.) thus acquiring a unique and distinct role in carrying out
materials-based research within the CNR-INFM organization. SuperMat has also
obtained the certification related to the Quality Management System UNI-ENISO:9001 as it concerns the “Managing and fulfillment of research, consulting and
testing activities in the area of Condensed Matter Physics” with particular emphasis on
“Transport phenomena in superconducting materials” and “Interplay between
superconductivity and magnetism”.
This report summarizes the activities of the Laboratory in the last 4 years (2005 –
2008) and offers a picture of SUPERMAT as it is now. Further information is
available at the website http://supermat.physics.unisa.it/.
Salerno, December 2008
Sandro Pace
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SuperMat is the only CNR- INFM Laboratory whose scientific activity is fully
devoted to the study of the superconductivity and superconducting materials. For this
reason SuperMat still intends to be a reference pole, in the national scenario, for:
 the synthesis and the study of new superconducting materials and the interplay
between superconductivity and magnetism. In particular, in recent years
SuperMat has achieved a leader position in the growth of high quality single
crystals.
 the current transport phenomena in the superconducting materials and their
applications to the electro-technical devices, standing as candidate to be the
scientific reference for their development in the “Obiettivo 1” E.U. regions.
In the next future SuperMat intends to reinforce its original mission also with the aid
of funding which will be obtainable in the framework of the PON 2007-13, MIUR,
and of the MSE and POR2007-13 Campania. With this funding SuperMat intends, in
particular, to reinforce the research activity related to the synthesis of new materials
and to increase the number of materials grown as single crystals. The range of growing
pressure and temperatures will be extended in such a way to synthetise materials
which exhibit, at higher temperatures, a high toxicity level.
In the study of the electric transport phenomena SuperMat intends to buy a cryogenfree system supplemented with a superconducting magnet ranging up to 16 T, a field
value not reachable in facilities operating in Italy. This choice will allow to perform
measurements in high magnetic fields in a relatively cheaply way also on nonsuperconducting materials. A big demand on the latter already exists on the National
territory as proved by a recent investigation performed in the last year by MIUR on
“medium and large infrastructures”. Finally, SuperMat intends also to further reinforce
its role as a reference point for electro-technical applications, in the Regions of the
Convergence of EU. For this reason the relationship with CRIS-Ansaldo, the only
industrial group working in the field of superconductivity in the Region of Objective
1, will be deepened.
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Scientific Report 2005-2008
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The organizational structure of SuperMat is shown in the figure below. To achieve the
Scientific & Technological objectives of SuperMat, the management activity of the
Director is supported by the consultative work of two Advisory Committees: the
SuperMat Internal Committee (SIC) and the International Scientific Committee (ISC).
According to the managing demands of Supermat, the Director can eventually
nominate a vice-director (assistant manager).
The SIC is composed by five members: the Director, the responsible of each
Commessa and two members selected among the associated and the staff members.
The SIC has an advising role for the selection and approval for the launch of scientific
projects as proposed by researchers of SuperMat. The role of the SIC is also to provide
a support in the choice of strategic actions to be undertaken for improving the research
quality, the level of the scientific and technology objectives as well as the impact of
the achieved results. The SIC will meet at least three times for year. At the end of each
meeting, together with the Director they will consider the possibility of having an
extra meeting in between those already scheduled.
The ISC is composed of four members coming from qualified Research Institutions
with high expertise in the fields related to the scientific activities of SuperMat. The
ISC is nominated by the Director of INFM who selects four eminent scientists within a
list proposed by the Director of SuperMat. The ISC has the role to review the activities
related to the Commessa 1 and 2 for the achievement of the scientific and
technological objectives. In particular, the function of the ISC is to cooperate with the
Director to evaluate the status of the project lifecycle and advancement within each
„Commessa‟. Moreover, the role of the ISC is to give recommendations and
suggestions about the proposals given by the SIC for eventual launch of new research
lines within each „Commessa‟. The ISC will meet once for year. In exceptional cases,
they will consider the possibility of having an extra meeting in the same year.
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SuperMat is the first scientific CNR centre which has successfully implemented the
Quality Management System. In particular, it concerns the 'Planning and fulfillment of
research activities, consulting and testing in the area of condensed matter physics'
with particular emphasis on “Transport phenomena in superconducting materials”
and “Interplay between superconductivity and magnetism” in compliance with the
standard UNI EN ISO 9001-2000. The Quality Management Systems applies to the
different operative labs within the SuperMat and to the S&T processes there executed.
The function of the Quality Management System is to have a periodic review of the
processes inside the SuperMat. This structure reduces the risks of uncontrolled
processes, naturally introduces the function of preventing and improving actions for
any running process, as well as sets a reference for the internal coordination among the
researchers operating in different SuperMat labs.
The Quality Management Certificate has been released by ITALCERT in the
framework of the action of Quality Centre of the University of Salerno.
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Research Staff – CNR-INFM
Mario Cuoco. Born on 7th August 1973 in Salerno (Italy). March
1996: Master Degree in Physics at University of Salerno. February
2000: Ph.D. in Physics at University of Salerno. April 1998-July
1999: visiting researcher at the Max Planck Institute, Stuttgart
(Germany). October 2002-September 2003: Marie-Curie Fellow at
the CNRS, Grenoble (France).Since July 2002: Researcher at the
CNR-INFM SuperMat. Member of the Organizing Committee of
the Conference on "Ruthenate and rutheno-cuprate materials:
theory and experiments", 2001 October, Vietri sul Mare, Italy and
SATT XI, March 2002, Vietri sul Mare, Italy. Referee of Physical
Review and Physical Review Letters. Member of the group for the
implementation of the Quality Management System at CNR-INFM
SuperMat in compliance with the standard UNI EN ISO 9001-2000. Research: properties of
systems with competing superconductivity and magnetism; modelling of electronic, magnetic
and transport properties of oxides. Co-author of about 60 articles on refereed international
journals.
Filippo Giubileo. Born 17th of September 1974 in Avellino, Italy,
received the master degree (cum laude) in Physics in 1998 and the
PhD in Physics in 2002 from the University of Salerno, Italy. Part
of his PhD studies were made at the Groupe de Physique des
Solides, University of Paris 6 (France), working at the idea of using
superconducting (MgB2) probe for the Scanning Tunneling
Microscopy. Since November 2003 he is Researcher at the CNRINFM Laboratorio Regionale SuperMat, in Salerno. He is author
of more than 30 articles in international refereed scientific journals
and he has participated to several international conferences. He
was the convenor of the Exploratory Workshop “Interplay between Superconductivity and
Magnetism at Nannometer Scale” financed by the European Science Foundation and held in
Paestum in 2008. His research activity is centred on superconductivity and on fabrication
and characterization of nanoscale devices. During the last three years he developed large
experience in low temperature STM/AFM/MFM, introducing a new mode of operation for
studying the vortex phase in superconductors using STM named the lazy fisherman method
(LFM).
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Marcello Gombos (Napoli, 6th/09/1966), degree: Physics
("Federico II" University of Napoli, 1995), PhD: Physics (University
of Salerno, 2000). His PhD work was partly carried out at ICMABCSIC (Barcelona, Spain). “Materials Science and Technology” (20052007) and “Electric and Electronic Measurements” (2007-2008)
Contracted Professor at SUN (Napoli). SuperMat Researcher since
2004. He grew Y123 (YBa2Cu3Oz) by Bridgman and Nd123 by TopSeeded Melt Texturing (TS-MTG), developing a model for Nd-Ba
substitutions. He worked on Gd1212 (GdSr2RuCu2Ok
synthesis. He studied GdSrRuCuO phase diagram line Gd1210Gd1212-CuO by TG-DTA. To study coexisting magnetic order and
superconductivity, he began TS-MTG of Gd1212. Recently started work on iron-based and
other non-conventional superconductors. He collaborates with many research centers,
ICMAB-CSIC, UPC (Spain), University of Genova and more. He participated to many
international and national conferences. He published almost 40 works.
Gaia Grimaldi. 1996 Master Degree in Physics, 2001 Ph.D. in
Physics at Salerno University with a research activity at ENEA
Research Center in Frascati (Rome) at the Superconductivity
Laboratory. In 2000 visiting researcher at Technical University of
Munich. Since 2003 Researcher at CNR-INFM Regional
Laboratory SUPERMAT in Salerno. The main scientific interests
have been static and dynamical properties of Josephson junction
devices. Critical current measurements of YBCO films deposited
on bicrystal substrates as function of temperature, magnetic field
intensity and angular orientation. I-V measurements on YBCO
coated conductors as well as Ic measurements by Hall probe
magnetometry. Magnetic properties of MgB 2 within the project “Superconducting Magnet
development based on diboruro of magnesium”. Transport and magnetic properties of
ReBaCuO thin films (Re=Sm, Gd, Eu). Vortex dynamics in type-II superconductors by
measurements of critical velocity and non equilibrium phenomena in the interaction between
vortices and material defects. Co-author in more than 25 papers on international journals.
Nadia Martucciello. Received her master degree in Physics
cum laude in 1994 and PhD in Physics in 1998 from University of
Salerno, Italy. The main activity in these years was the
experimental research in condensed matter physics, in particular
on low temperature superconducting devices, non linear dynamics
in Josephson junctions and spin polarized electron transport in
Superconductor/Ferromagnet junctions. In the last year her
research activity was focused on Superconducting Single Photon
Detectors based on Niobium Nitride nanowires. She has carried
out her activity in collaboration with international institutes for
research.
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Annalisa Paolone. Born 15th of July 1970 in Campobasso, Italy.
Master degree in Physics in 1993 and PhD in Material Science in
1997 at the University of Rome “La Sapienza”. Part of the PhD
studies and a Post-Doc experience were performed at the
Laboratoire pour l’Utilization du Rayonnement Electromagnetique
in Orsay, France. Her experimental studies concerned the infrared
spectra of high Tc superconductors and manganites. Since 1999, she
worked in Rome on anelastic spectroscopy of high Tc
superconductors and carbon nanotubes. Since October 2004 she is
Researcher of CNR-INFM at Laboratorio Regionale SuperMAT in
Salerno. She is author of more than 70 papers published in peer
review journals. Her present scientific activity is focused on superconductors and on
materials for solid state hydrogen storage.
Antonio Vecchione. Born on 1963 in Naples, received his Physics
degree from University of Naples “Federico II” in 1990 and Ph.D. in
Physics from University of Salerno in 1994. At the first stage of his
career, he has been scientific guest of the University of Negev
working on noise in superconducting devices. Since 1996 he has been
INFM researcher taking part in various scientific projects. He has
worked as Associate Professor at the Kyoto University in 2004. His
research activity is mainly focused on superconducting and magnetic
perovskite oxides. Recently, he developed experience on single crystal
growth and characterization studying single phase and eutectic
samples based on the strontium ruthenates and electron doped high
Tc superconductors. He has organized international conferences and has been responsible for
SuperMat of the Quality Management System. He is author of more than 80 publications in
international scientific journals, editor of books, coordinator of proposals at large scale
facilities and referee of several scientific journals.
Rosalba Fittipaldi is a postdoctoral fellow at the CNR—INFM
Laboratorio Regionale SuperMat in Salerno, since 2006. After
graduating with a master degree in Physics (cum laude) at the
University of Salerno in 2000, Rosalba received the Master of
Science in Information Technology from the University of Sannio in
Benevento. In 2002, she moved to ENEA in Rome as postgraduate
student. She received the PhD in Physics from the University of
Salerno in 2006. She made part of her PhD studies at Kyoto
University, in Japan. Her main research interest is in studying the
interaction between superconducting and magnetic materials,
mainly in the ruthenate physics. In particular, her activity is
devoted to the crystal growth, by floating zone technique, of the
Ruddlesden-Popper ruthenate compounds, Sr n+1RunO3n+1. A recent interest includes the
study of electron doped high-temperature superconductors. In June 2005 she was awarded
the “Young Authors Awards” in the Matter Materials and Devices Meeting.
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Zujian Ying. Born on January 15, 1973, in Fujian, China,
received PhD in Physics in 1999 at Lanzhou University, China. He
has worked as a postdoctoral researcher in Zhejiang University,
China, Instituto de Fisica da UFRGS, Brasil, Centro Brasileiro de
Pesquisas Fisicas, Brasil, and University of Salerno, Italy. He also
has ever served as an associate professor in Hangzhou Teachers
College, China. Since July 2008, he has been working as a
temporary researcher at CNR-INFM SuperMat, in close
collaborations with ChongQing University, China. He is author of
about 25 articles of international scientific journals, he has research
interests ranging from one-dimensional systems, spin ladder
materials, ultracold atomic Fermi gases, superconducting metallic grains, to ferromagnetic
superconductors. His current research is focused on the coexistence of ferromagnetism and
superconductivity as well as the interplay of polarizations and pairing correlations in Fermi
gases.
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The following list includes professors, researchers and technicians who
belong to university or other research institutions and conduct most of their
research and projects within SUPERMAT
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Carmine ATTANASIO
Adolfo AVELLA
Fabrizio BOBBA
Giovanni CARAPELLA
Roberta CITRO
Giovanni COSTABILE
Anna Maria CUCOLO
Giovanni FILATRELLA
Umberto GAMBARDELLA
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Angela NIGRO
Canio NOCE
Sandro PACE
Massimiliano POLICHETTI
Alfonso ROMANO
Paola ROMANO
Aniello SAGGESE
Matteo SALVATO
Consiglia TEDESCO
The following list includes post-doc members and PhD students who have
worked at their thesis at SUPERMAT in the period covered by this report.
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Maria Giuseppina ADESSO
Natascia ANDRENACCI
Maria Antonietta BOFFA
Regina CIANCIO
Carla CIRILLO
Emiliano DI GENNARO
Paola GENTILE
Veronica GRANATA
Anita GUARINO
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Antonio LEO
Maria LONGOBARDI
Samanta PIANO
Albino POLCARI
Francesca RUSSO
Matteo TROPEANO
Rene' YAMAPI
Danilo ZOLA
The following list includes collaborators who have contributed at the activity
developed at SUPERMAT in the period covered by this report.
 Andrea AUGIERI
 Serghej PRISCHEPA
 Ciro CASTIELLO
 Paolo SABATINO
 Luigi FALCO
 Alessandro SCARFATO
 Eugenio LIPPIELLO
 Daniela SISTI
 Mariacristina LUBRITTO
 Vincenzo SURRENTI
 Giorgio PASOTTI
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Nowadays, SUPERMAT carries out fundamental and applied research in condensed
matter physics. Starting from the experience developed, since many years, at the
INFM Research Unit of Salerno, the Laboratory proposes itself as a pole in the field
of superconductivity and its interplay with magnetism, both from an experimental and
theoretical point of view. The main focus is on the fabrication of materials, the
analysis of their structural, morphological, transport and magnetic properties, as well
as on the fabrication and investigation of hetero-structures.
The Research Activity in SUPERMAT is structured in two main scientific lines:
1. Interplay between Superconductivity and Magnetism
• Superconductivity and magnetism in pure and eutectic strontium ruthenate crystals
• Synthesis and Growth of High Tc Superconducting Bulk Materials
• Unconventional superconductivity and itinerant ferromagnetism:
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Mechanisms for coexistence and proximity phenomena
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Unconventional superconductivity and strongly correlated systems
• Interplay between superconductivity and magnetism in S/F multilayers
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Study of the interplay between ferromagnetism and superconductivity in YBa 2Cu3O7x/La0.7Ca0.3MnO3 artificial ferromagnetic/superconductor heterostructures
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Proximity effect in low temperature S/F/S heterostructures
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Periodicity, symmetry and finite dimensions of S/F multilayers
• Ferromagnet/Superconductor hybrids.
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F/S/F superconducting valves
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Spin polarized tunneling in F/I/S heterostructures
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Quantum transport and pumping in mesoscopic heterostructures
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Anelastic spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction
characterization of superconducting materials
Scientific Report 2005-2008
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2. Transport Phenomena in Superconducting Materials
• Superconducting tapes and wires for applications
• Magnetic properties of superconductors for fundamental and applied research
• Josephson Junctions and power grids in the Kuramoto model
• Study of superconducting Nd1-xCexCuO4-δ thin films and single crystals
• Non linear effects in the dynamics of Abrikosov vortices in type-II superconducting
films
• Thin Nb films deposited on porous substrates
• Tunneling Spectroscopy on Superconducting Materials
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Study of the Superconducting properties of the two-band superconductor MgB2.
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Pairing State in unconventional superconductors by Point-Contact Andreev Reflection
Spectroscopy
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Tunneling spectroscopy on high Tc cuprates
Other activities
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Superconducting Single Photon Detectors
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Transport properties of organic materials
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Local field emission properties of partially aligned multiwalled carbon-nanotubes by Atomic
Force Microscopy
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Materials for solid state hydrogen storage
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The research in the field of superconductivity is oriented towards the understanding of
its fundamental mechanisms both in traditional low-Tc and in ceramics
superconductors as well as in magnesium diboride and in artificial layered
superconducting structures together with their possible applications.
Even though the transport phenomena in the presence of impurities and the H-T phase
diagram of type-II superconductors have been intensively studied, some points are still
not completely understood especially after the discovery of high temperature
superconductors. Also, applicative aspects of the superconducting materials have
received a big impulse due to the possibility of using materials which can operate
without the need of liquid helium as a refrigerating. From a theoretical point of view a
new interesting field emerged in connection with to the study of the coexistence of
competing orders such as superconductivity and magnetism. Moreover, the very recent
discovery of the new superconducting materials belonging to the family of Feoxypnictides has also given a new impulse to this research field.
At the Regional Laboratory “SuperMat” the research activity has been carried out in
the framework of two “Commesse”. One is named “Interplay between
superconductivity and magnetism”, the other is “Transport properties in
superconducting materials”.
The investigation of the interplay between superconductivity and ferro(magnetism)
has been devoted to the analysis of systems like transition metal oxides and heavyfermion compounds, hetero-structures as well as mesoscopic materials. From an
experimental point of view, the fabrication and characterization of single crystals,
artificial multilayers and polycrystalline compounds has been addressed to the
coexistence of magnetic ordering and superconductivity in pure and eutectic materials
based on Sr2RuO4 and Sr3Ru2O7, in Nb/(Cu,Pd)Ni and La(Sr,Ca)MnO/YBaCuO
systems and in rutheno-cuprates (bulk and films) materials. All these systems have
been studied at the SuperMat Laboratory by structural, morphological and
compositional analysis as well as by means of transport and magnetic investigations.
Scanning tunnel spectroscopy and atomic and magnetic force microscopy have been
used to study some of the produced compounds. Among the main results obtained in
the field of single crystals growth, the achievement of pure samples of strontium
ruthenates suitable for studies requiring sizeable and strongly oriented specimens is a
key aspect for understanding the properties of these complex materials. The
availability of samples has lead to measurements at large facilities using neutrons,
muons and many other characterizations based on synchrotrons (photoemission, XAS,
etc.) as well as other techniques such as magnetooptics and optical spectroscopy. The
activity on bulk samples has given interesting results on the rutheno-cuprate systems.
Important contributions towards the understanding of the coexistence of magnetic
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ordering and superconductivity have been obtained through EXAFS, point contact
spectroscopy and magneto-transport studies. The modelling in the framework of these
activities has covered many issues such as the structure of the pairing in presence of
spin imbalance, the conditions for the coexistence of superconductivity and
ferromagnetism in rutheno-cuprates and heavy-fermions (i.e. UGe2 and URhGe), the
occurrence of a spin polarized superconducting state for granular systems, the
proximity effect in S/F (superconductor/ferromagnet) hybrid structures with different
interface conditions assuming unconventional pairing in the S side and different types
of itinerant ferromagnetism from weak spin polarization to half-metallic limit, the
proximity between a chiral p-wave superconductor and a normal (or ferromagnetic)
system for interpreting properties of eutectics materials based on Sr2RuO4 and
Sr3Ru2O7. Among the main results, it has been unveiled the better microscopic
conditions for having a ground state with a coexistence of superconductivity and
ferromagnetism as well as it has been extracted the fingerprints of such configuration.
Still, it has been shown that the proximity effect in S/F structures depends on the
mechanism that yields the ferromagnetism and on the symmetry of the
superconducting pairing.
The research activity of the “Commessa” “Transport properties in superconducting
materials” has been carried out following two main lines. The first one named “Effetti
dissipativi nel trasporto di corrente in presenza di impurezze o di interfacce tra
materiali diversi” was mainly devoted to the study of more fundamental aspects, the
second one “Realizzazione di un avvolgimento di MgB2” was characterized by highly
applicative activities. In the frame of the first research line, the activities have been
mostly devoted to the study of the electric transport properties in superconducting
layered structures with a special attention to the causes which may influence the
interface transparency in Nb/PdNi and Nb/CuNi bilayers. In particular, resistive
transition measurements in these systems have been performed with and without an
external magnetic field (applied both in the parallel and in the perpendicular direction
with respect to the plane of the substrate). A detailed and comparative investigation of
the electric and magnetic properties in thin films of weak ferromagnetic alloys such as
PdNi and CuNi has been also done. The problem of periodicity, symmetry and finite
dimensions of multilayers has been addressed by measuring resistive transitions in
Nb/PdNi and Nb/CuNi multilayers. I-V characteristic measurements have been
performed on structured Nb films and Nb/Py bilayers as a function of the temperature
and the perpendicular magnetic field. The investigation has been done for high values
of the bias current, close to the dynamic instability, and the role of the ferromagnetism
on the critical velocity and the superconducting order parameter has been inferred. In
the case of Nb thin films the interaction between the Abrikosov lattice and the pinning
centers has been studied with a special attention to the study of the associated nonequilibrium processes. Finally, high-quality NdCeCuO thin films and single crystals
have been realized by sputtering technique in Argon and Oxygen atmosphere and by
the floating zone technique, respectively. After a preliminary structural, compositional,
morphological and electrical characterization, photoemission spectroscopy
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measurements using soft and hard X-Rays have been performed at the TASC
laboratory in Trieste. The experimental data allowed to discriminate between the
properties due to the surface layer and those related to the massive compound.
Magnetic and transport properties have also been performed on MgB2 tapes in the
superconducting phase. Special care has been paid to the study of the thermo-magnetic
instability, observed at temperatures below 10 K, which is responsible for flux jumps
which can be detected in magnetization measurements as a function of the external
magnetic field. As concerns the activity related to the development of magnesium
diboride based superconducting magnets, this activity has been developed in a strong
collaboration with the Ansaldo-CRIS. Within this project we have analyzed many
aspects concerning the MgB2 either as a superconducting material, or as a basic
component in a superconducting tape. The main target was to build a small magnet by
using MgB2 tape operated in a cryogen free environment. The target was fully attained
(in terms of field strength, 1T on the conductor, bias current, 100 A, and temperature
of operation, 20 K) within the prescribed time schedule.
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Many international collaborations characterize the scientific activities of both the
“Commesse” of the Regional Laboratory “SuperMat”. They are all strongly
connected to the different projects in which the researchers of the laboratory are
involved. The most relevant ones are the following:
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Jan Aarts and Prof. Peter Kes, University of Leiden;
Serghej Prischepa and Prof. V. Borisenko, BSUIR Minsk;
Alexander Lykov, Lebedev Institute, Moscow;
Rene Flukiger, University of Geneva;
B. Caplin, Imperial College, London;
Dimitri Roditchev, Institute des Nanosciences de Paris
M. Aprili, CNRS Paris;
A. Sidorenko, University of Ausburg;
N.F. Pedersen, The Technical University of Denmark;
B. Malomed, University of Tel Aviv;
J.F. Zasadzinski, Argonne National Laboratory;
E. Baca Universidad del Valle;
Mikhail Kupriyanov, Moscow State University;
Rudolf Huebener, University of Tuebingen;
P. Horsch, Max-Planck-Institute, Stuttgart;
A.M. Oles, Institute of Physics, Jagellonian University, Krakow;
J. Ranninger, CNRS Grenoble;
Yoshiteru Maeno, University of Kyoto;
E. Olsson, Chalmers University, Goteborg;
H. Habermeier, Max Planck Institut, Stuttgart;
Victor Moshchalkov, Katholieke Universiteit Leuven;
A. Mackenzie, University of St. Andrews;
G. Balakrichnan, University of Warwick;
X. Obradors, ICMAB Barcelona.
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In the perion 2005 – 2008 the SUPERMAT Laboratory has been involved in several
national and international research project as listed below:
Piano Operativo Nazionale – Title: Laboratorio per la crescita di materiali avanzati e
lo studio di nanostrutture in materiali e dispositivi superconduttori (coordinator: prof.
S. Pace) – Budget: € 950.400,00
FAR 6337 – Title: "Sviluppo di magneti superconduttori basati su diboruro di
magnesio" in collaboration with CRIS-Ansaldo – Naples (coordinator: prof. S. Pace) –
Budget: € 850.000,00
Progetto di ricerca Regione Campania, L.R. n.5/2002 – Correnti di "depairing" in
strutture ibride superconduttore/ferro magnete (coordinator: prof. C. Attanasio) –
Budget: € 14.000,00
Progetto di ricerca Regione Campania, L.R. n.5 – Title: Effetti dissipativi in
condizioni dinamiche in superconduttori non convenzionali (coordinator: dr. G.
Grimaldi) – Budget: € 25.000,00
Fondo italiano per la ricerca di base – Title: Micro-sistemi basati su polimeri
cristallini nanoporosi per il rilevamento nell'ambiente di inquinanti organici volatili
(local coordinator: dr. A. Nigro) – Budget: € 20.000,00
ENEA Commercial project – Title: Caratterizzazioni termiche e elettriche in
corrente alternata di nastri a base di superconduttori ad alta temperatura di transizione
(coordinator: dr. U. Gamdardella) – Budget: € 28.000,00
Magaldi Commercial project – Title: Progettazione di un sistema di evacuazione e
controllo qualità sui contatori criogeniche per ossigeno terapia (coordinator: dr. U.
Gamdardella) – Budget: € 5.000,00
European Science Foundation Exploratory Workshop – Title: "Interplay Between
Superconductivity and Magnetism at Nanometer Scale"(coordinator: dr. F. Giubileo) –
Budget: € 14.000,00
Progetto di ricerca Regione Campania, L.R. n.5 – Title: Stati superconduttivi in
metalli ferromagnetici: meccanismi e topologia di fasi miste (coordinator: dr. M.
Cuoco) – Budget: € 14.835,00
Moreover, the collaboration with local industries (Metzeler – Battipaglia (SA), Lasped
– Cava de‟ Tirreni (SA)) has lead to commercial projects for the use of SuperMat
equipments (SEM, diffractometers) (coordinator: A. Vecchione) – Total budget: €
7000,00
The outreach of the activity related to the project “FAR 6337” covered different
national and international manufacturers of MgB2 wires and tapes, i.e. Columbus
Superconductors, Genova, I, Edison SpA, Milano, I, and Hypertech, Columbus, OH.
The industrial partner for this industry research project was the CRIS Ansaldo, Naples,
together with the magnet was designed and wound. Moreover, the activity carried out
18
Scientific Report 2005-2008
Structure
in collaboration with ENEA was largely focused on the study and characterization of
YBCO coated conductor. Basic aspects of YBCO film growth on bi-epitaxial
structures have been investigated, among which we mention the angular effects of
applied magnetic field on the critical current. Moreover, stability of commercial
YBCO long tapes under working conditions, i.e. with full current bias and thermal
instabilities, have been studied. Further to experiments performed in cryogen free
environment, also numerical models have been developed to understand the features of
quench propagation. In fact this problem sets strong limits to the applications of HTc
in magnet technology, requiring the development of new protection systems. The
outreach of different manufactures of YBCO coated conductors, like American
Superconductors Co. and SuperPower Inc., provided us with an updated YBCO tape
quality. In this way the obtained results are meaningful, as they concern the actual
YBCO tapes used to produce prototypes.
Scientific Report 2005-2008
19
Structure
In the last year, several proposal have been submitted for the use of different large facilities at
Laboratories around the Europe. Below it is reported the list of the approved proposals.
1. Paul Scherrer Institute – Villigen (CH) Beamline: GPS
Title: Superconductivity, metamagnetism and quantum criticality in Ruthenates
2. Paul Scherrer Institute – Villigen (CH) Beamline: LTF
Title: Superconductivity, metamagnetism and quantum criticality in Ruthenates
3. ILL – Grenoble (F) Beamline: D10
Title: Metamagnetic transition in the eutectic system Sr3Ru2O7 – Sr4Ru3O10
4. Elettra – Trieste (IT) Beamline: Bach
Title: Effect of the bilayer coupling on the electronic structure of correlated Ru oxides
5. ESRF – Grenoble (F) Beamline: BM28
Title: X-ray Resonant Study of Sr2Ru1-xTixO4: Towards investigations of the p-wave
superconducting state in Sr2RuO4
6. High Magnetic Field Laboratory – Grenoble (F)
Title: Angle resolved high field magnetic torque measurements on Sr4Ru3O10 single
crystals and Sr3Ru2O7 – Sr4Ru3O10 eutectic crystals
7. Paul Scherrer Institute – Villigen (CH) Beamline: LTF
Title: Musr spectroscopy on NdCeCuO single crystals
8. Paul Scherrer Institute – Villigen (CH) Beamline: Swiss Light Source
Title: RIXS spectroscopy on NdCeCuO and LaSrCuO thin films
20
Scientific Report 2005-2008
Structure
SuperMat is involved in many educational activities and in promoting scientific
exchange within the topics of its “Commesse”. SuperMat has supported the teaching
activities of the Training Course in the Physics of Strongly Correlated Systems at the
International Institute for Advanced Scientific Studies. SuperMat is in strong contact
with PhD school in Physics of the Dipartimento di Fisica dell‟Università di Salerno.
Many
students
of
this
PhD
school
(http://www.fisica.unisa.it/Personal/utenti.asp?Dottorando) worked for their thesis
within the SuperMat laboratories profiting of equipments and the scientific experience
of the personnel. Moreover, SuperMat has organized many seminars and scientific
training
and
activities
called
“Tuesday
matter”
(http://www.fisica.unisa.it/TuesdayMatter) to introduce Master and PhD students as
well as young researchers to the topic related to the “Commesse”. SuperMat has given
a strong contribution with its researchers and the “didactic kits” to the organization of
all the Exposcuola editions involving many primary and high schools (more than
10.000 visitors per year) also organizing visits to the laboratories and giving lectures.
SuperMat organized an Exploratory Workshop financed by the European Science
Foundation on Interplay between Superconductivity and Magnetism at Nanometer
Scale (http://supermat.physics.unisa.it/ew) held in Paestum (Salerno), Italy on June
2008 and convened by Filippo Giubileo. The workshop had participation from across
Europe and involved recognized leading experts as well as independent researchers
with leadership potential. The small scale workshop has provided an ideal platform for
focus on the topic and for all participants to contribute to discussions and plan followup collaborative work (i.e. EUROCORES program) on the interplay between
magnetism and superconductivity.
Scientific Report 2005-2008
21
Structure
22
Scientific Report 2005-2008
Structure
Date
Speaker
Affiliation
Title
27/11/08
Vesna Mitrovic
Department of Physics Brown University
182 Hope Street, Box 1843 Providence, RI
24/6/08
Giancarlo Panaccione
Laboratorio Nazionale TASC- INFM –
CNR in AREA Science Park
17/6/08
Maurizio Ferretti
Dipartimento di Chimica - Università di
Genova
10/6/08
Patrizia Tedesco
Dipartimento di Fisica "E.R. Caianiello" Università degli Studi di Salerno
6/5/08
Giovanni Filatrella
Universita' del Sannio e Laboratorio
Regionale SuperMat
Response of unconventional
superconductor to magnetic field
Photoemission Spectroscopy as
a tool for materials science: from
surface to bulk sensitivity.
As-layered superconductors: a
physico-chemical approach
La tecnica mSR e le sue
applicazioni alla
superconduttività ed al
magnetismo
Le giunzioni Josephson come
prototipo per la sincronizzazione
di oscillatori non lineari.
5/5/08
Fulvio Parmigiani
Dipartimento di Fisica, Università degli
Studi di Trieste and Sincrotrone Trieste,
Basovizza, Trieste
Correlation effects in CuGeO3
and La1-xNaxMnO3
8/4/08
Canio Noce
Dipartimento Fisica "E. R. Caianiello" Università degli Studi di Salerno
11/3/08
Serghej L. Prishepa
Belarussian State University of Informatics
and RadioElectronics
4/3/08
Geetha Balakrishnan
31/1/08
D. Carbone
29/1/08
Danny Mannix
Institut Neel, CNRS-Grenoble, France
22/1/08
Danny Mannix
Institut Neel, CNRS-Grenoble, France
13/12/07
Achille Angrisani Armenio
17/7/07
Giuseppe Milano
12/6/07
Giacomo Ghiringhelli
INFM/CNR COHERENTIA and
Dipartimento di Fisica, Politecnico di
Milano
17/5/07
Tetyana Shapoval
Leibniz Institute for Solid State and
Materials Research Dresden
17/4/07
Emanuela Carleschi
20/2/07
M.G. Blamire
29/11/06
Umberto Scotti di Uccio
Department of Physics, University of
Warwick, Coventry CV4 7AL, UK
ID01- ESRF Rue Jules Horowitz 38043
Grenoble, France
ENEA - Frascati Research Centre Fusion
Division - Superconductivity Laboratory
Via Enrico Fermi, 45 - 00044 Frascati
(Italy
Modeling Lab for Nanostructure and
Catalysis (MolNaC) Department of
Chemistry University of Salerno
C.N.R. - Istituto Nazionale per la Fisica
della Materia Laboratorio Nazionale TASC
Beamline BACH
Department of Materials Science,
Cambridge University, UK
CNR/INFM Coherentia Napoli e Università
degli Studi di Cassino
New high Tc superconductors:
quaternary oxypnictides RE-OM-Pn with
RE=(La,Ce),M=(Fe,Ni) and
Pn=(As,P)
Multimode phase transition in
Superconductor/Ferromagnet
heterostructures
High quality single crystals
using Optical Furnaces
Radiazione di sicrotrone: usi (ed
abusi)
Investigating Electronic
Orderings by Synchrotron X-ray
Scattering (part II)
Investigating Electronic
Orderings by Synchrotron X-ray
Scattering
Crescita e caratterizzazione di
Film Epitassiali di YBa2Cu3O7-x
depositati con tecnica MOD
TFA-modificata
Multiscale Modelling in
Polymer Science: from atomistic
to mesocale simulations
Orbital occupation and neutral
excitations in cuprates and
manganites studied with
resonant soft x-ray
spectroscopies
Study of vortex pinning
mechanism in YBCO thin films
by low-temperature MFM
Charge transfer dynamics in a
misfit cobaltite studied by
resonant PES
Vortex Cutting in Type II
Superconductors
La superficie di film e cristalli di
SrTiO3
Scientific Report 2005-2008
23
Structure
31/10/06
Istituto di Struttura della Materia (ISM),
CNR
"Coherentia" INFM-CNR and Dipartimento
di Fisica, Università di Roma La Sapienza,
Piazzale Aldo Moro 2, I-00185 Roma, Italy
Proprietà magnetiche di
interfaccia: sistemi Exchange
Bias
La spettroscopia infrarossa e il
suo contributo alla fisica dei
superconduttori
24/5/06
P. Calvani
27/4/06
Sebastian Bergeret
Dept. de Física Teórica de la Materia
Condensada CV Facultad de Ciencias
Universidad Autónoma de Madrid Spain
Odd Triplet Superconductivity
in Superconductor-Ferromagnet
Structures: A Review
Carla Cirillo
Dipartimento di Fisica "E.R. Caianiello"Università di Salerno
Superconducting proximity
effect in Nb/PdNi hybrids:
probing the role of the
ferromagnet
22/11/05
Eva Olsson
Microscopy and Microanalysis Applied
Physics Chalmers University of
Technology - Göteborg
In-situ probing of transport
properties of carbon nanotubes
and oxide interfaces using TEMSTM
8/11/05
Anatolie Sidorenko
Institute of Applied Physics Academy of
Sciences of Moldova, Kishinev, Moldova
Proximity effect and quasiLOFF-state in
Superconductor/Ferromagnet
layered systems
11/10/05
Sergio Pagano
Università di Salerno - Dipartimento di
Fisica
Superconducting Detectors
27/9/05
Victor V. Moschalkov
Chairman of the ESF Programme
`VORTEX` - Katholieke Universiteit
Leuven, Belgium
Vortex-Antivortex matter in
nanosuperconductors
14/2/06
24
Sara Laurenti
14/7/05
Giusy Valvo
ST Microelectronics - Catania
Rivelatori al silicio per
applicazioni scientifiche:
progettazione e realizzazione in
STMicroelectronics
7/7/05
Rene Yamapi
Department of Physics, Faculty of Sciences,
University of Douala, PO Box: 24157
Douala, CAMEROON
Some recent research in Nonlinear Dynamics and its
applications in
electromechanical Engineering
5/7/05
Laura H. Greene
Department of Physics, University of
Illinois at Urbana-Champaign -USA
Point Contact Spectroscopy of
CeCoIn5: Andreev Reflection at
the heavy-fermion
superconductor interface
19/4/05
Andrea Augieri
INFM -Università di Tor Vergata
Correlated pinning and transport
properties in YCaBaCuO thin
films
30/3/05
Yoshiteru Maeno
Department of Physics and International
Innovation Center, Kyoto University,
Kyoto 606-8502, Japan
Newly Discovered
Superconductivity in a Layered
Silver Oxide
8/3/05
Roberta Cimberle
CNR-IMEM-Istituto dei Materiali per
l'Elettronica ed il Magnetismo
Superparamagnetismo in Sistemi
Magnetici Nanostrutturati
22/2/05
Filippo Giubileo
Laboratorio Regionale INFM-SUPERMAT
Scanning Probe Microscopy: A
World of Surface Science
Techniques
18/1/05
Annalisa Paolone
INFM, Laboratorio SUPERMAT-Salerno
Università di Roma "La Sapienza"
Present and perspectives of
carbon nanotubes
Scientific Report 2005-2008
In the following, some research activities are presented:
Interplay between Superconductivity and
Magnetism
 Superconductivity and magnetism in pure and eutectic strontium
ruthenate crystals
 Synthesis and Growth of High Tc Superconducting Bulk Materials

Rutheno-cuprate

Analysis of Properties of Top-Seeded Melt-Textured Grown Nd1Ba2Cu3O7-
Samples
 Unconventional superconductivity and itinerant ferromagnetism:

Mechanisms for coexistence and proximity phenomena
 Interplay between superconductivity and magnetism in S/F multilayers

Proximity effect in low temperature S/F/S heterostructures

Periodicity, symmetry and finite dimensions of S/F multilayers

Study of the interplay between ferromagnetism and superconductivity in
YBa2Cu3O7-x/La0.7Ca0.3MnO3 artificial F/S heterostructures
 Ferromagnet/Superconductor hybrids

F/S/F superconducting valves and Spin polarized tunneling in F/I/S
heterostructures
Transport properties in superconducting
materials
 Superconducting Tapes and wires for applications
 Magnetic properties of superconductors for fundamental and applied
research
 Josephson Junctions and power grids in the Kuramoto model
 Study of superconducting Nd1-xCexCuO4-δ thin films and single
crystals
 Non linear effects in the dynamics of Abrikosov vortices in type-II
superconducting films
 Thin Nb films deposited on porous substrates
 Tunneling Spectroscopy on Superconducting Materials

Study of the Superconducting properties of the two-band superconductor MgB2.

Pairing State in unconventional superconductors by Point-Contact Andreev
Reflection Spectroscopy

Tunneling spectroscopy on high Tc cuprates
Other
Activities

Superconducting Single Photon Detectors

Transport properties of organic materials

Local field emission properties of partially aligned multiwalled carbon-nanotubes by
Atomic Force Microscopy
Interplay between
Superconductivity and
Magnetism
Superconductivity and magnetism in pure and eutectic strontium ruthenate
crystals
This research activity aims to understand the complex phenomenology of strontium
ruthenates [1,2] through different operative tasks involving synthesis optimization,
physical characterization and theoretical modeling. The three phases were and will
be strongly correlated each other. On a general point of view, the main goal of this
research is to link the control of the single crystal growth with the achievement of
materials whose physical properties can be tailored and understood within a
suitable theoretical frame. More in detail, the nature of the superconductivity and of
the magnetism as well as their interplay in the single phase and in the eutectic
samples based on Sr2RuO4 Sr3Ru2O7, Sr4Ru3O10 is the object of the investigation
for this activity. Concerning the single crystal growth, the target is to optimize the
processes involved in the growth in order to control the quality of the single phase
materials as well as the percentage of the two
constituent phases in the eutectic crystal.
Such achievement has allowed to obtain
interesting results [3–7] and in the future it
can possibly open new routes for exploring
competing collective phenomena upon novel
conditions in the frame of strongly correlated
materials. Part of this study deals with the
crystallographic changes due to the interfaces
between the different constituents, the
crystallographic matching between the two
phases in the same crystal and the detection
and control of the possible occurrence and of
spurious phases or defects evaluating their
amount. In the next future, to further refine
the investigation, it will be performed the
Fig.1. Single crystal growth of
strontium ruthenate by floating zone
analysis of the superconducting and magnetic
technique.
behaviour of these crystals in the field and
temperature (H,T) diagram changing magnetic field orientation. In addition, using
large facilities probes will be pursued extracting the response of the systems in the
high magnetic field region of the phase diagram. In the same spirit, to get deeper
insight in the static and dynamical properties of the materials, this research activity
will take advantage of probes such as photoemission, muon and neutron
spectroscopy as well as elastic-inelastic x-ray spectroscopy. Finally, it will be
developed a suitable methodology to compare and analyze the experimental results
of the produced samples.
Scientific Report 2005-2008
29
Interplay between
Superconductivity and
Magnetism
References
[1] A. P. Mackenzie and Y. Maeno, Rev. Mod. Phys. 75 657 (2003).
[2] S. A. Grigera et al., Science 306 (2004) 1154, ibid R. A. Borzi et al., Science 315 214 (2007).
[3] R. Fittipaldi, A. Vecchione, S. Fusanobori, K. Takizawa, H. Yaguchi, J. Hooper, R.S. Perry and
Y. Maeno, J. Cryst. Growth 282, 152 (2005).
[4] R. Fittipaldi, D. Sisti, S. Pace, A.Vecchione, Crystal Growth and Design 7, 2495 (2007).
[5] S. Kittaka, S. Fusanobori, S. Yonezawa, H. Yaguchi, Y. Maeno, R. Fittipaldi and A. Vecchione,
Phys. Rev. B77, 214511 (2008).
[6] R. Fittipaldi, A. Vecchione, R. Ciancio, S. Pace, M. Cuoco, D. Stornaiuolo, D. Born, F. Tafuri,
E. Olsson, S. Kittaka, H. Yaguchi and Y. Maeno, Europhysics Letters 83, 27007 (2008).
[7] C. Mirri, L. Baldassarre, S. Lupi, M. Ortolani, R. Fittipaldi, A. Vecchione, and P. Calvani, Phys.
Rev. B 78, 155132 (2008).
30
Scientific Report 2005-2008
Interplay between
Superconductivity and
Magnetism
Synthesis and Growth of High Tc Superconducting Bulk Materials

Synthesis and Growth of Rutheno-cuprate Materials Bulk Samples
Interest in Gd1212 (GdSr2RuCu2O8) is due to the observed coexistence of
superconductivity and magnetic ordering in the same cell [1]. Until now no
definitive word has been said on its magnetic order nature [1,2,3,4], also because of
this material’s great anisotropy. Progress may come by analysing
crystallographically oriented samples, but RuO2 and O2 losses [5, 6] prevented, up
to now, Gd1212 single crystals and superconducting films growth. Melt-Textured
Growth (MTG) appears then as the main route to obtain oriented samples. TopSeeded (TS-) MTG induces structural orientation of the re-solidified sample along
a chosen crystallographic axis (generally the c-axis), so that it results constituted by
a few (or even one) crystallographic “domains”. So, beside the production of
Gd1212 powders and sintered samples for analysis and film fabrication [7,8,9], we
put a great effort on the search for optimal conditions to achieve Gd1212 oriented
samples by TS-MTG. Our work is based on the similarity of Gd1212 melting
reaction in air (Gd1212=> Gd1210(=GdSr2RuO5,5)+liquid) and Nd123
(=NdBa2Cu3O7) one (Nd123=>¼(Nd4Ba2Cu2O10)+liquid) [10]. To confirm this
observation and identify the best starting powders mixture, we analysed, by TGDTA, Gd1212-based mixtures melting in air along the whole CuO-Gd1212Gd1210 line [5, 6], and Gd1212 melting in modified atmospheres.
Melting produced liquid scarcity prevented since now large oriented samples
fabrication [11]. Anyway, interesting information on the physics of Gd1212 have
been obtained by our samples analysis [12, 13, 14], that appear slightly textured on
the 100 m scale and present Gd1210 precipitates (fig.1). We also studied
precursor powders composition impact [15] and spurious phases formation [16] in
MTG samples.
I)
II)
Fig.2: PLOM images of Gd1212 TS-MTG pellets areas: I) boundary between two domains
(enhanced by grey line and arrows). II) pores (black spots, one is marked by a white triangle )
and precipitates (brighter spots, one is marked by a white star ).
Scientific Report 2005-2008
31
Interplay between
Superconductivity and
Magnetism
Finally, we analysed Nd doped Gd1212 individuating solubility limits of both Gd
rich Gd1-xNdxSr2RuCu2O8 and Nd rich (Nd1-xGdx,Sr2)(Ru,Cu2)O9 phases [17].
I)
II)
Fig.3: I) Nd-rich and Gd-rich phases ratios in NdxGd1-xSr2RuCu2Ok mixtures (by XRD data) with
solubility limits fit. II) DTA results.
References
[1] C.Bernhard, et al, E.J.Ansaldo, Phys. Rev. B, 59, pp. 14099, 1999.
[2] J.W.Lynn, B.Keimer, C.Ulrich, C.Bernard, J.L.Tallon, Phys. Rev. B, 61, pp. R14964, 2000.
[3] A.C.McLaughlin, J.P.Attfield, Phys. Rev. B, 60, pp. 14605, 1999.
[4] M.R.Cimberle, et al, J. Magn. Magn. Mater. 316, e529, (2007).
[5] M.Gombos, R.Ciancio, A.Vecchione, S.Pace, J. Mater. Res. 22, 1579, (2007).
[6] M.Gombos, R.Ciancio, A.Vecchione, S.Pace, Physica C 460-462, 522, (2007).
[7] A.Paolone, et al, Physica C 467, 167, (2007).
[8] R.Fittipaldi, et al, J. Phys. Chem. Solids, 67, 613, (2006).
[9] A.Guarino, et al, Phys. Stat. Sol (c), 3, 3073, (2006).
[10] L.Bauernfeind, W.Widder, H.F.Braun, J. Low Temp. Phys. 105, 1605, (1996).
[11] R.Ciancio, et al, IEEE T. Appl. Supercon., 15, 3149, (2005).
[12] C.Attanasio, et al, Physica C, 411, 126. (2004).
[13] S.Piano, et al, Phys. Rev. B, 73, 064514, (2006).
[14] M.Polichetti, et al, Phys. Stat. Sol. (c), 3, 3061, (2006).
[15] Impact of the Starting Powder Composition on GdSr2RuCu2O8 Melt-Textured Processes,
R.Ciancio, et al, to be published in IEEE T. Appl. Supercon..
[16] R.Ciancio, M.Gombos, S.Pace, M.Polichetti, A.Vecchione, D.Zola, preprint.
[17] M.Gombos, et al, IEEE T. Appl. Supercon. 17, 2965, (2007).
32
Scientific Report 2005-2008
Interplay between
Superconductivity and
Magnetism

Analysis of Properties of Top-Seeded Melt-Textured Grown Nd1Ba2Cu3O7- Samples
Nd123 (NdBa2Cu3O7) has the highest superconducting critical temperature
(Tc96K) among RE123, a high Jc (Jc(77K)105A/cm2, for H1-5T) and high
upper critical magnetic field Hc2 [1, 2]. For this reasons Nd123 is a good candidate
for applications like superconducting flywheel motors and so on. The main
limitations are the slowness of TS-MTG fabrication processes, (72h/cm), and the
brittleness of oriented samples. Nd123 electrical transport and magnetic features
may be related to Nd ions substitutions into Ba crystal sites [3], expressed by the
formula Nd123(x) = Nd1+xBa2-xCu3O7-d+x/2: this effect leads to local Tc decrease
that may provide additional pinning centres, increasing Hc2. Our interest focuses on
TS-MTG samples mechanical fragility [4], and on cation substitution [5].
Cation substitution results an entropy driven process, statistically very well
simulated by inserting in Nd123(x) free energy a mean field term  x4/3. Least
square fits on experimental data show that this term leads to highly substituted
phase clusters formation inside the Nd123 matrix [5]. Strong temperature
dependence of the minimum substituted phase is one of the most interesting
predictions made by our model. Spontaneous cleavage of TS-MTG Nd123 samples
leads to their complete fragmentation into parallelepiped splinters in a few days.
Cracks occur along the main crystallographic axes as can be deduced by EBSD
measurements on splinters and this allows to measure the anisotropy of Nd123
critical current density Jc, that results to be almost an order of magnitude higher
along a-b plane than along c axis [4]. Cracks formation and development appear to
be related to room temperature oxygenating processes and relaxation of mechanical
stresses due to oxygen induced tetragonal-orthorhombic phase transition [4]. To
prevent this phenomenon, good results have been obtained by the use of MultiSeeded bars [6] that also present very good characteristics of inter-domain c-axis
misalignment (less than 4°) and a significant processing time reduction.
I)
II)
Fig.1: I) Fragmented cylindrical (=5cm) Nd123 TS-MTG sample 7 days after growth. II) Upper
view (a) and side view (b) of Nd123 four-seeded MTG bar after polishing. Domain boundaries are
near 0.7 cm, 2.5 cm and between 3.8 and 4 cm marks.
References
[1]. S.I. Yoo, and R.W. McCallum, Physica C 210, 147, (1993)
Scientific Report 2005-2008
33
Interplay between
Superconductivity and
Magnetism
[2]. S. I. Yoo, N. Sakai, H. Takaichi, T. Higuchi, M. Murakami, Appl. Phys. Lett., 65 No. 5, 633,
(1994)
[3]. E.A. Goodilin, N.N. Oleynikov, E.V. Antipov, R.V. Shpachenko, G.Yu. Popov, V.G.
Balakirev, Yu.D. Tretyakov, Physica C 272, 65, (1996).
[4]. Tri-dimensional Crack Structure and Fragility in NdBa2Cu3O7- Bulk Samples M.Gombos,
V.Gomis, R.Ciancio, D.Zola, A.E.Carrillo, A.Vecchione, M.Polichetti, S.Pace, and
X.Obradors, preprint.
[5]. M.Gombos, E. Varesi, P.Tedesco, A.Vecchione, and S.Pace, Philos. Mag., 88, 1389, (2008).
[6]. M.Gombos, V.Gomis, A.Vecchione, R.Ciancio, R.Fittipaldi, A.E.Carrillo, S.Pace, X.Obradors,
IEEE T. Appl. Supercon., 15, 3137, (2005).
34
Scientific Report 2005-2008
Interplay between
Superconductivity and
Magnetism
Unconventional superconductivity and itinerant ferromagnetism: mechanisms
for coexistence and proximity phenomena
The discovery of materials like those belonging to the class of rutheno-cuprates
(i.e. (Gd,Eu)RuSr2Cu2O8) and to the class of the heavy-fermions (i.e. UGe2,
URhGe, e ZrZn2), has been posing new questions on the mechanisms, the pairing
symmetry and the topological patterns for the coexistence of superconductivity and
itinerant ferromagnetism. Though different from the previous topic, similar
questions also occur when dealing with the proximity phenomena at the interface
between a spin singlet/triplet superconductor and a ferromagnet. Novel features in
the proximity effect between a superconductor and a ferromagnet have been found
for the case of unconventional pairing or near the so called half-metallic regime.
The recent research activity has been focused on the following problems: A) the
mechanisms for the coexistence of metallic ferromagnetism and singlet
superconductivity (SF phase), with special emphasis to the occurrence of
inhomogeneous and/or modulated pattern for the amplitude of the ferromagnetic
(FM) and SC order parameter, B) the case of two coupled and spatially separated
FM and SC electron liquids with a specific geometry, as it is realized in the
rutheno-cuprate class of materials (RESrRuCuO with RE=Gd,Eu,Sm), C) the
possibility of having triplet pairing coexisting with ferromagnetism as related to the
class of heavy-fermions materials (UGe2 and URhGe), D) the proximity effect
between an unconventional SC (i.e. triplet chiral p-wave, singlet d-wave) and an
itinerant FM in the regime of small and large spin polarization. For the part (A), the
new and crucial ingredient is that the metallic ferromagnetism is not due, as in
previous studies, to a rigid shift in the positions of the majority and minority spin
bands (Stoner exchange), but it is a consequence of a change in the relative
bandwidth of electrons with up and down spin polarization [1]. The main finding of
such analysis is represented by the determination of the microscopic conditions that
allow for such a coexisting state and the characterization of the resulting quantum
configurations both in the regime of weak and strong pairing [2]. Referring to the
case of the rutheno-cuprates materials (B), the research activity has continued on
the characterization of the FM and SC patterns in a topology where the two
electron liquids are spatially separated but can communicate via different
exchange/charge transfer mechanisms. Concerning the part C, we have constructed
a theory for itinerant ferromagnetism coexisting with a nonunitary superconducting
state, where only the majority-spin band is gapped and contains line nodes, while
the minority-spin band is gapless at the Fermi level. Our study has been motivated
by recent experimental results, which indicate that this may be the physical
situation realized in the heavy-fermion compound UGe2 [3]. Finally (D), we have
analyzed the proximity effect within a junction made of an unconventional
superconductor (US) and a ferromagnet in the clean limit with high barrier
transparency [4]. We have shown that the two above mentioned mechanisms for
Scientific Report 2005-2008
35
Interplay between
Superconductivity and
Magnetism
ferromagnetism lead to different features as concerns the formation at the interface
of dominant and subdominant superconducting components, as well as their
propagation in the ferromagnetic side.
Figure:
a)
schematic representation of the
majority and minority spin
bands for a Stoner ferromagnet
and
a
spin
dependent
bandwidth ferromagnet,
b)
sketch of the phase separation
in energy between the magnetic
and superconducting sector that
may occur in the coexisting
phase of a single component
system,
c)
view of the junction between a
ferromagnet
and
a
superconductor with different
pairing symmetries.
References
[1] M. Cuoco, P. Gentile and C. Noce, Physical Review Letters 91, 197003 (2003); Journal of
Physics and Chemistry of Solids 67, 157 (2006).
[2] Z.-J. Ying, M. Cuoco, C. Noce, and H.-Q. Zhou, Physical Review B 74, 012503 (2006);
Physical Review B 76, 132509 (2007). Physical Review Letters 100, 140406 (2008). Physical
Review B 78, 104523 (2008).
[3] J. Linder, I.B. Sperstad, A.H. Nevidomskyy, M. Cuoco, and A. Sudbø, Physical Review B 77,
184511 (2008).
[4] M. Cuoco, A. Romano, C. Noce, and P. Gentile, Physical Review B 78, 054503 (2008).
36
Scientific Report 2005-2008
Interplay between
Superconductivity and
Magnetism
Interplay between superconductivity and magnetism in S/F multilayers

Proximity effect in low temperature S/F/S heterostructures
Proximity effect in Superconducting (S)/Ferromagnetic (F) systems is a very
active field of research, due both to the rich physics originated from the
coexistence of two competing orderings, and to the numerous suggestions for
the engineering applications of these heterostructures [1]. In these systems
the superconducting order parameter does not simply decay in the
ferromagnetic metal, but also oscillates along the direction perpendicular to
the interface. Signatures of this inhomogeneous state are: nonmonotonic
dependence of the transition temperature as a function of the ferromagnetic
layer thickness, negative critical current and reversed density of states in
Josephson and tunnel S/F/S -junctions, respectively [1]. Our investigation
started with a preliminary study of the S/normal metal (N) coupling in Nb/Pd
[2,3], Nb/Cu [4] and Nb/Ag [4] structures with a particular attention to the
quality of the interfaces between the two deposited material. The S/F
coupling has been successively studied in Nb/Pd1-xNix and Nb/Cu1-xNix
systems for different Ni concentrations. Pd1-xNix and Cu1-xNix are in fact
weak ferromagnets, whose magnetic strength can be varied in the meV range
changing the Ni percentage in the alloy. In this way the coupling between
superconductivity and ferromagnetism can be studied in a wider range of
thicknesses. In this contest a detailed investigation of the magnetic and
transport properties of the alloys was performed [5].
The investigation on S/F systems was mainly focused on critical temperatures
[6,7] and critical fields measurements [8]. In the case of Nb/Pd1-xNix bilayers
the dependence of the critical temperature on the S and F layers thicknesses
has been analyzed [6,7] and the nonmonotonic Tc(dF) behaviour was
observed. The experimental data were theoretically interpreted in order to
evaluate the transparencies of the S/F barriers, together with the
ferromagnetic coherence lengths, F, which measure the penetration of the
Cooper pairs in the F layers. Depairing current measurements were also
employed as a more sensitive tool to probe the order parameter changes
below Tc. In absence of vortex motion, the depairing current density, J dp, is
the ultimate critical current that a superconductor can support. The
inhomogeneous character of the superconducting order parameter in Nb/PdNi
bilayers was studied by directly comparing the information from Tc and Jdp
upon varying the PdNi layer thickness dPdNi [7].
Scientific Report 2005-2008
37
Interplay between
Superconductivity and
Magnetism
Moreover the study of the interplay between superconductivity and
magnetism has been extended to systems in which the two constituents are a
high-Tc superconductor (HTS) and a fully spin-polarized ferromagnetic
manganite, namely YBCO/LCMO systems [9]. In particular we studied the
dependence of the activation energy on the external magnetic fields in
LCMO/YBCO/LCMO trilayers with two different YBCO layer thicknesses.
The experimental data, extracted by resistive measurements, suggest that the
vortex lattice is in a 2D regime even in the case of a thick YBCO layer. This
result has been interpreted on the basis of the recent hypothesis on the
existence of injection of spin polarized particles from LCMO into YBCO for
these systems.
Nb/PdNi bilayers with dNb=14 nm and variable ferromagnetic
thickness, dPdNi. Tc(dPdNi) dependence (open symbols) compared
to Jdp(dPdNi) behaviour (closed symbols) [7]
References
[1] A. I. Buzdin, Rev. Mod. Phys. 77, 935 (2005)
[2] C. Cirillo, S.L. Prischepa, M. Salvato, and C. Attanasio, Eur. Phys. J. B 38, 59 (2004)
[3] S.Y. Gavrilkin, A.N. Lykov, A.Y. Tsvetkov, Y.V. Vishniakov, C. Attanasio, C. Cirillo,
and S.L. Prischepa, Phys. Rev. B 74, 64509 (2006)
[4] A. Tesauro, A. Aurigemma, C. Cirillo, S.L. Prischepa, M. Salvato, and C. Attanasio,
Supercond. Sci. Technol. 18, 1 (2005)
[5] G. Iannone, D. Zola, A. Angrisani Armenio, M. Polichetti, and C. Attanasio, Phys. Rev. B
75, 64409 (2007)
[6] C. Cirillo, S.L. Prischepa, M. Salvato, C. Attanasio, M. Hesselberth, and J. Aarts, Phys.
Rev. B 72, 144511 (2005)
[7] C. Cirillo, A. Rusanov, C. Bell, and J. Aarts, Phys. Rev. B 75, 174510 (2007)
[8] A. Angrisani Armenio, C. Cirillo, G. Iannone, S.L. Prischepa, and C. Attanasio, Phys. Rev.
B 76, 24515 (2007)
[9] M. Salvato, C. Attanasio, F. Bobba, G. Calabrese, C. Cirillo, A.M. Cucolo, A. De Santis,
and A. Vecchione, Eur. Phys. J. B 51, 79 (2006)
38
Scientific Report 2005-2008
Interplay between
Superconductivity and
Magnetism
Study of the interplay between ferromagnetism and superconductivity in YBa 2Cu3O7x/La0.7Ca0.3MnO3 artificial ferromagnetic/superconductor heterostructures
It has generally been believed that, within the context of the BCS theory of
superconductivity, the conduction electrons in a metal cannot be both
ferromagnetically ordered and superconducting. In spite of this effect the discovery
of ternary rare-earth compounds where magnetism and superconductivity coexist,
has opened a new field of research.
In the last thirty years, therefore, several “intrinsic” materials exhibiting this effect
have been identified, and artificial Ferromagnetic/Superconductor heterostructures
have been realized and investigated with the aim of achieving a better
understanding of the interplay between superconductivity and magnetism. This was
motivated also by the search for possible applications of such composite systems in
the device materials electronic industry. It has been verified that colossal
magnetoresistance manganites have good structural compatibility with high-Tc
superconductors, and are a rich reservoir of spin-polarized charges, which can be
used for spin injection studies. Injection of spin-polarized electrons into a
superconductor with energy greater than the energy gap induces a non-equilibrium
state in the superconductor by creating non-equilibrium population of spins in the
material, both by scattering and pair breaking phenomenon. Also in these hybrid
systems, thus, it appears of primal importance to understand as the electrical and
magnetic properties of these materials are modified by the simultaneous presence
of these two competing orders.
Magnetic Force Microscopy image of La0.7Ca0.3MnO3 thin films on (a)NGO, (b)LAO, (c)STO.
Our research fits in this interesting field and consists in the experimental
investigation of the interaction between superconductivity and magnetism in
artificial YBa2Cu3O7-x/La0.7Ca0.3MnO3 heterostructures.
In order to study the Ferromagnetic/Superconducting systems, we have fabricated
and investigated, in detail, the structural, electrical and magnetic properties of the
single layer of LCMO. The X-ray measurements and TEM analysis have
evidenced the high epitaxiality of our films. From the electrical measurements we
have evidenced a variation of the metal-insulator temperature and a reduction of the
resistivity with the thickness of the LCMO layer, due to different factors, in
Scientific Report 2005-2008
39
Interplay between
Superconductivity and
Magnetism
particular to the strain inducted by the substrate. We have also studied the
modification of the resistance applying an external magnetic field. The
magnetization as function of the temperature has been measured placing the thin
films in an external magnetic field (H) parallel to the sample surface in such way to
neglect the demagnetizing effects. From the magnetization we infer a Curie
temperature (TC) in good agreement with the metal-insulator transition, measured
by transport properties. Then the LCMO thin films have been characterized by
Magnetic Force Microscopy al low temperature (10 K) and in magnetic field up to
6 Tesla. We have studied LCMO thin films with different thicknesses and with
different substrates (STO, ALO, NGO) to verify the effect of these on the magnetic
properties of the material. We have verified that the dynamics of the magnetic
domains depend both the thickness of the LCMO film and the choice of the
substrate. Bilayers (YBCO/LCMO) and trilayers (LCMO/YBCO/LCMO) have
been fabricated in situ by a multi-target DC sputtering in high oxygen pressure.
X-ray and TEM analysis are carried out to guarantee the epitaxiality of the
heterostructures and the good interfaces. Electrical measurements in bilayers and
trilayers have evidenced a reduction of the superconducting critical temperature
explaining in term of the injection of spin-polarized electrons from LCMO to
YBCO. Then magnetization measurements on LCMO/YBCO/LCMO trilayer, in
zero field cooling and in field cooling, have shown a Curie temperature lower than
the single LCMO layer, evidencing the influence of the YBCO layer.
The existence of magnetic and superconducting order have been investigated in a
superlattice of 10 layers of La0.7Ca0.3MnO3/YBa2Cu3O7-x. These analysis have been
carried out by polarized neutron reflectometry, SQUID magnetometry, and
resistivity measurements. The magnetization line shapes observed by SQUID
magnetometry under zero-field-cooled and field-cooled conditions imply an
inhomogeneously disordered magnetic state of the manganite blocks. Then
resistivity measurements under field-cooled conditions reveal strong perturbations,
which imply that the ferromagnetic La0.7Ca0.3MnO3 blocks contain strong
magnetic disorder with perturbations coupled to the magnetic order via charge
hopping between domains. Polarized neutron reflectometry under zero-field-cooled
conditions, below the superconducting transition, reveal a noncollinear
ferromagnetic structure, coherent across half the superlattice blocks. Across the
superconducting transition, the noncollinear components are perturbed by the
superconducting order and attempt to align with the dominant ferromagnetic order.
Additionally, the magnetic correlation length increases
from half the superlattice structure to a magnetic structure correlated across the
complete superlattice. At temperatures above the superconducting transition, the
noncollinear magnetic components and the magnetic correlation length relax to the
structure observed below the superconducting transition.
40
Scientific Report 2005-2008
Interplay between
Superconductivity and
Magnetism

Periodicity, symmetry and finite dimensions of S/F multilayers
Superconductivity in layered systems is closely related to the spatial behavior
of the order parameter. In recent years the influence of finite dimensions of
superconductor/normal metal (S/N) multilayers on the superconducting phase
nucleation has been studied. In particular the finiteness of multilayers requires
to take into account the strong influence of the sample edges imposing
appropriate boundary conditions in the Ginzburg-Landau (GL) equations. In the
framework of this model it was shown that the position where the
superconducting phase nucleates affects, for example, the resistive transition to
the superconducting state [1], the shape of the H-T phase diagram [2] as well as
the Hc2() dependence [3] in S/N multilayers, where Nb is the superconducting
material and Cu and Pd are the normal ones.
1.0
(a)
(z)
0.5
1.0
(b)
0.5
0.0
-0.5
-1.0
0
40
80
120
160
200
Figure. Anomalous wave function for
the Nb/PdNi multilayer with Nbil=9,
dPdNi=2.2 nm and dNb=19 nm.
Configuration (a) is the one with the
smallest, n = 0, possible number of
nodes; configuration (b) is the one
with n = 8, the maximum number of
nodes, where the “-phase” is realized
at all the different interfaces. By
vertical solid lines the PdNi and Nb
layers are marked. The dashed line
corresponds to the position of the
symmetry plane of the sample [5].
z(nm)
More recently this study was extended to the case of S/F trilayers [4] and
multilayers with different numbers of bilayers (Nbil) [5]. In these systems, in
fact, the possible realization of the so called "-phase" makes this investigation
even more appealing. We investigated the nucleation of superconductivity in
finite multilayers consisting of weakly ferromagnetic Cu41Ni59 and Pd81Ni19 and
superconducting Nb. In Nb/Cu41Ni59/Nb trilayers we observed unusual
broadening of the superconducting resistive transitions, which is confined to the
thickness regime where the “0-” transition takes place. A model, based on the
occurrence of networks of Josephson junctions in the system has been proposed
[4]. Since an increase of the number of S/F layers in the structure should result
in a further enlargement of the anomalies in the transition curves, an intensive
investigation of finite Nb/Pd81Ni19 multilayers is in progress. In particular
Scientific Report 2005-2008
41
Interplay between
Superconductivity and
Magnetism
theoretical simulations showed the correlation between the spatial distribution
of the superconducting wave function and both the resistive R(T) transitions of
the samples and the critical temperature behavior Tc(Nbil) of the series [5].
Indeed the unequivocal message from the experiments is that the large Nbilmultilayers have transition widths which are somehow connected to the
different possible order parameter configurations, starting with the 0-node
symmetric one.
References
[1] V.N. Kushnir, S.L. Prischepa, M.L. Della Rocca, M. Salvato, and C. Attanasio, Phys. Rev.
B 68, 212505 (2003).
[2] V.N. Kushnir, S.L. Prischepa, C. Cirillo, M.L. Della Rocca, A. Angrisani Armenio, L.
Maritato, M. Salvato, and C. Attanasio, Eur. Phys. J. B 41, 439 (2004).
[3] S.L. Prischepa, C. Cirillo, V.N. Kushnir, E. A. Ilyina, M. Salvato, and C. Attanasio, Phys.
Rev. B 72, 24535 (2005)
[4] S.L. Prischepa, C. Cirillo, C. Bell, V.N. Kushnir, J. Aarts, C. Attanasio, and M. Yu.
Kupriyanov, JETP Letters 88, 375 (2008)
[5] S.L. Prischepa, V.N. Kushnir, E.A. Ilyina, C. Attanasio, C. Cirillo, G. Iannone, A.
Vecchione, R. Fittipaldi, J. Aarts. Physics, Chemistry and Application of Nanostructures.
Nanomeeting 2007 (Minsk, Bielorussia), World Scientific, Singapore, 2007.
42
Scientific Report 2005-2008
Interplay between
Superconductivity and
Magnetism
Ferromagnet/Superconductor hybrids.

F/S/F superconducting valves and Spin polarized tunneling in F/I/S heterostructures
In the last three years the main research activity was focused on the experimental
investigation of Ferromagnet/Superconductors heterostructures with a particular
interest in spin-polarized tunneling. The Ferromagnet/Superconductor (FS) hybrids
have attracted a lot of interest due to the possibility to control superconductivity by
the exchange field (spin switch) or by the stray fields generated by the ferromagnet
(superconducting valve). Tunneling measurements play a key role in spin polarised
transport experiments, particularly, a series of experiments on F/I/S junctions have
provided that the tunnel current is spin polarised even outside the ferromagnetic
region.
Using deposition techniques such as rf-magnetron sputtering and thermal
evaporation,
both
Ferromagnet/Supercoductor
heterostructures
and
Ferromagnet/Normal metal were fabricated in order to study the spin effects in
current transport.
Therefore, we have made transport measurements in a superconducting Co/Nb/Co
trilayer based on elemental ferromagnetic Co and elemental superconducting Nb.
The trilayer behaves as a superconducting valve, can be operated at liquid helium
temperature and can switch from superconductive to normal state in weak applied
in plane magnetic fields. Current-Voltage curves, critical currents as a function of
temperature and magnetic field as well as preparation of superconductive or
resistive state have been addressed. Data analysis suggests that the
superconducting valve behavior can be accounted for by a glassy vortex phase
induced in the superconductor by the stray fields from domain walls proliferating
around the coercive fields of the ferromagnetic electrodes.
We also have made magneto-transport measurements on Permalloy/Niobium
bilayers patterned in a Hall strip geometry, with Permalloy allowing a weak stripe
domain regime. After application of a weak magnetic field in the plane of the
bilayer and perpendicular to the transport current, the strip behaves as a
superconducting diode, with very different positive and negative depinning
currents. The role of the two depinning currents can be reversed by inverting the
sign of the preparing magnetic field, resulting in a bistable behavior of the diode,
useful to operate the bilayer as a non-volatile superconducting valve, as shown in
the Figure below. The observed behavior can be accounted for the stray fields
from Bloch domain walls at the edges of the strip that modulate the distribution of
the stray fields from the stripe domains in the ferromagnetic layer generating an
asymmetric and bistable magnetic forces landscape for the Abrikosov vortices
moving in the superconducting layer.
Scientific Report 2005-2008
43
Interplay between
Superconductivity and
Magnetism
(a) Voltage versus Field curve during a loop of the
magnetic field at 4.25 K at fixed positive bias
current. (b)
Magnetic field waveform used to prepare the ON or
OFF states together with the voltage waveform of
the device.
[1] G. Carapella, F. Russo, V. Granata, N. Martucciello, and G. Costabile, “Spin polarized electron
transport in a superconductor/ferromagnet junction with intermediate barrier strength”, Supercond.
Sci. Technol. 19 (2006) 1191–1195;
[2] F. Russo, G.Carapella, V. Granata, N. Martucciello, and G. Costabile, “Pseudo spin-valves with
Al as normal spacer layer: GMR and search for spin switch behaviour”, Eur. Phys. J. B 60, 61
(2007);
[3] G. Carapella, F. Russo, And G. Costabile, Phys. Rev. B 78, 104529 (2008);
[4] G. Carapella, V. Granata, F. Russo, And G. Costabile, Submitted Prl (2008);
[5] F. Russo, G. Carapella, And G. Costabile, Submitted Sust (2008).
44
Scientific Report 2005-2008
Transport properties in
superconducting materials
Superconducting Tapes and wires for applications
The MIUR project ―FAR 6337 – Sviluppo magneti basati su Diboruro di
Magnesio‖ was one of the main activities pursued during the last 3 years. The
industrial partner for this industry research project was the CRIS-Ansaldo, Naples,
with which the magnet was designed and wound. Within this project we analyzed
many aspects concerning the MgB2 either as superconducting material, or as basic
component in a superconducting tape. The main target was to build a small magnet
by using MgB2 tape operated in a cryogen free environment. The targets were fully
attained within the prescribed time schedule: field strength, 1T on the conductor;
bias current, 100 A; and temperature of operation, 20 K.. The outreach in this
activity covered different national and international manufacturers of MgB2 wires
and tapes, i.e. Columbus Superconductors, Genova, I, Edison SpA, Milano, I, and
Hypertech, Columbus, OH. The final tests were carried out in SuperMat laboratory.
(ref. 1-5)
We also focused to the study and characterization of YBCO coated conductor.
Basic aspects of YBCO film growth on bi-epitaxial structures have been
investigated, among with the angular effects of applied magnetic field on the
critical current. Moreover stability of commercial YBCO long tapes under working
conditions, i.e. with full current bias and thermal instabilities, have been studied.
Further to experiments performed in cryogen free environment, also numerical
models have been developed to understand the features of quench propagation. In
fact this problem set strong limits to the applications of HTc in magnet technology,
requiring the development of new protection systems. The outreach of different
manufactures of YBCO coated conductors, like American Superconductors Co. and
SuperPower Inc., provided us with an updated YBCO tape quality. In this way the
obtained results are meaningful, as they concern the actual YBCO tapes used to
realize prototypes. (ref. 6-12)
Finally the laboratory provided a substantial contribution in Nb3Sn wire
development carried out in a specific INFN program, NTA-CANDIA, devoted to
the achievement of high current wires useful for the high field dipole, 15 T and
beyond, foreseen for the next generation of accelerators (after LHC). In fact the
SuperMat laboratory is equipped with a 16T magnetometer, suitable instrument to
perform characterization of these wires, saving time and costs with respect to direct
transport current of several kA, and also providing complementary information to
the effective filament diameter and flux jumps (cryogenic instabilities) behaviour,
which often occurs in these kind of wires. (ref. 13-15)
References
[1] C. Tarantini, et al., Physical Review B 73 (2006), 134518
[2] U. Gambardella, et al., IEEE Applied Superconductivity 17 (2007), 2937
[3] A. Santoni, et al., Applied Physics A 86(2007), 485-490
Scientific Report 2005-2008
45
Transport properties in
superconducting materials
[4] E. Perini, et al., IEEE Applied Superconductivity 17 (2007), 2730
[5] C. Tarantini, et al., Physica C: Superconductivity 463-465 (2007), 211
[6] Celentano, et al., IEEE Applied Superconductivity 15 (2005), 2691
[7] A. Augieri, et al., Physica C: Superconductivity 437-438 (2006), 17
[8]A. Augieri, et al., Superconductor Science and Technology, 20 (2007), 381
[9] A. Augieri, et al., Physica C: Superconductivity 460-462 (2007), 829
[10] Michela Greco, et al., IEEE Applied Superconductivity 17 (2007), 2722
[11] V. Galluzzi, et al., IEEE Applied Superconductivity 17 (2007), 3628
[12] A. Vannozzi, et al., IEEE Applied Superconductivity 17 (2007), 3436
[13] Michela Greco, et al., IEEE Transaction on Magnetics, 16 (2006) 1164
[14] P. Fabbricatore, et al., Nucl. Phys. (Proc. Suppl.) 154 (2006), 157
[15] P. Fabbricatore, et al., Superconducting Science and Technology 20 (2007), L34
46 Scientific Report 2005-2008
Transport properties in
superconducting materials
Magnetic properties of superconductors for fundamental and applied research
In a type-II superconductor, below the critical temperature TC and below a lower
critical field HC1(T), there is no penetration of magnetic flux inside the sample and
the superconductor is in the so-called Meissner state. The susceptibility  of
superconductor is largely diamagnetic (-1). When the applied field Ha exceeds
an upper critical field HC2(T) > HC1(T) or T > TC the entire specimens reverts to the
normal state and the susceptibility becomes slightly positive. This large variation of
the susceptibility allows us to measure the TC and HC2(T) of superconducting
samples by means of a magnetometer or a susceptometer. In Fig.1 the
susceptibility of a recently discovered family of superconductors, measured by
means of the A.C susceptibility technique, is reported. In the left panel, the TC
depends on the applied D.C magnetic field allowing to evaluate HC2(T) of the
superconductor.
0.0
1607 Hz
HAC = 1 Oe
ZFC
-0.2
0.10
0 Oe
50Oe
1 kOe
5 kOe
30 kOe
90 kOe
-0.6
-0.8
-1.0
M(emu)
0.05
-0.4

2K
3K
5K
0.00
-0.05
-0.10
0
5
10
15
T (K)
20
25
30
-100 -80 -60 -40 -20
0
20
40
60
80 100
Ha (kOe)
Fig.1 (Left) Susceptibility of the iron-based superconductor LaO0.92F0.08FAs as function of the
temperature measured applying a D.C. field up to 90 kOe. (Right) Magnetization loop of
LaO0.92F0.08FAs superconductor measured at different temperatures.
If Ha is in between HC1(T) and HC2(T), the magnetic flux penetrates the
superconductor as quantized (φ0 = h/4c = 210−15 Wb) flux lines also called
vortices or fluxons, generating the so-called ―mixed state‖. As Ha increases, the
density of vortices in the material becomes larger. In type II superconductors
without defects, they form an exagonal lattice, and an arbitrary slight current causes
their motion due to the effect of a Lorentz-like force fL = j × φ0. This motion
produces dissipation, and to avoid it fL can be counterbalanced by the force due to
the defects in the material, which act to pin the vortices (―pinning force‖, fP). The
presence of pinning destroys the regularity of the vortex lattice, and generate
hysteresis in the magnetic properties, as shown in the magnetization loops of Fig. 1
(right panel), measured on an iron-based LaO0.92F0.08FeAs superconductor at
different temperatures. From the magnetization measurements the superconducting
current density can be evaluated. Moreover, changing the field sweep rate (dHa/dt)
or applying an a.c. field (hAC), by means of inductive magnetic measurements it is
Scientific Report 2005-2008
47
Transport properties in
superconducting materials
possible to investigate the strongly non linear voltage-current (I-V) characteristic of
the superconductors at electrical field values lower than those at stake in the
standard I-V measurements [1-2].
-
Dissipative regimes
To move a pinned fluxon the Lorentz-like force has to be strong enough to win
the pin force. Therefore, below the critical current density ( jc) a d.c. current can
flow without dissipation. The jc of a superconductor can be larger than 106 A/cm2,
and therefore the superconducting wires can be used to realize electro-power
applications as magnets, cables for energy and so on.
For currents above jc, and for negligible thermal fluctuations, the fluxons move,
giving rise to a dissipative state called flux flow. If thermal fluctuations are present,
the vortices can be depinned by the thermal activation energy so that a ―flux creep‖
dissipating regime can arise long before the flux flow. In this case the
magnetization of the superconductor decays with time, following the general
behaviour given by: M (t )  Mi ln(1  t /  ) where Mi is the initial value of the
magnetization, and  is a macroscopic characteristic time. By analyzing the
temperature or the magnetic field dependence of this magnetic relaxation, the
pinning energy barrier overcome by the vortex can be evaluated. Flux creep in
cuprate superconductors as YBCO and BSCCO(2223), as well as MgB2 and the
recently discovered iron-based superconductor LaOFFeAs, has been studied by our
research group [1-2].
Moreover, the competition between the thermal and the magnetic diffusion
properties of superconducting materials at some external conditions can produce
avalanches of vortices and ―flux jumps‖, visible in the M(H) curves as abrupt steep
variations, and generating dissipation which can reduce the performance of cables
and wires. In our laboratory the flux jumps have been studied in MgB2 tapes with
various impurities (added to the superconducting matrix) and metallic sheets [3-4].
-
Vortex phase diagrams
The complete map of magnetic properties comes from the competition of five
energy terms: thermal energy, repulsive interaction between vortices, pinning
energy, current-vortex interaction energy, elastic energy of the vortex lattice. The
competition of these energies determines the flux dynamics and leads to a complex
B−T phase diagram in which the irreversibility line Birr(T) is crucial; in fact, since
it represents the boundary between the irreversible (jc≠0) and reversible (jc=0)
region of the magnetic properties, the highest field for the ‖undissipating‖ state is
Birr instead of Bc2.
The mechanisms governing the vortex dynamics of type-II superconductors in
the mixed state can be extensively studied by AC magnetic susceptibility (ac). In
particular, the real part of the first harmonic (’1), associated with the screening
properties of the sample, is proportional to the time average of the magnetic energy
48 Scientific Report 2005-2008
Transport properties in
superconducting materials
stored in the volume occupied by the sample, whereas the imaginary part (’’1) is
proportional to the energy converted into heat during one cycle of AC field.
When a state with irreversible magnetic properties is present in the material, the
current-voltage (I-V) characteristics exhibit a non-linear behaviour, corresponding
to the appearance of harmonics higher than the first one in the ac. Nevertheless, by
looking only at the third harmonics, both experimental and numerical results have
shown that, for a sample with given geometry and pinning properties, the shape of
the two components of the third harmonics is much influenced by the presence of
particular vortex dynamics regimes. So, this higher sensitivity of the third
harmonics to the vortex dynamics, together with the opportunity to compare the
numerical simulations and the experimentally measured curves, supplies a very
powerful tool to extract detailed information about the dynamics regimes
governing the AC magnetic response of superconducting samples.
The investigation of the vortex dynamics is performed on conventional and
high TC superconductors as well as in the new iron-based materials. The analysis of
the experimental data is also performed by means of numerical computation
solving the non linear differential equation of the magnetic field diffusion inside a
superconductor. [5-8]
In these last years ―SuperMat‖ has been involved in several projects regarding
superconducting large scale devices (like superconducting magnets) and the study
of the magnetic properties of the materials has supported the research involved in
the development of this kind of power applications.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
M. Polichetti, M.G. Adesso, D. Zola, J. Luo, G. F. Chen et al, Phys. Rev. B 78 224523 (2008)
D. Zola, C. Senatore, M. Polichetti and S. Pace, Phys. Rev. B 70, 224504, (2004)
D. Zola, M. Polichetti, M.G. Adesso, L. Martini, S. Pace, Physica. C 460-62, 795, (2007)
D. Zola , M. Polichetti, L. Martini, S. Pace, IEEE Trans. Appl. Supercond. 17 2734,(2007).
M. G. Adesso, D. Uglietti, R. Flukiger, M. Polichetti, S. Pace, Phys. Rev. B 73; 092513 (2006)
M. G. Adesso, M. Polichetti, D. Uglietti, et al., IEEE Trans. Appl. Supercond. 16, 1241 (2006)
M.G. Adesso, R. Flukiger, M. Polichetti et al., IEEE Trans. Appl. Supercond. 17, 2619 (2007).
M.G. Adesso, M. Polichetti and S. Pace, J. Phys.: Condens. Matter 20, 385211 (2008)
Scientific Report 2005-2008
49
Transport properties in
superconducting materials
Josephson Junctions and power grids in the Kuramoto model
Josephson junctions are nonlinear oscillators that, for practical purposes,
require synchronization. Synchrony of nonlinear elements is a widespread
phenomenon, not only in artificial electronic circuits, but also in natural systems
such as the classical example of fireflies that blinks simultaneously along the rivers
of the Far East [1]. Josephson junctions have been in fact mapped onto a generic
model for nonlinear synchronization, called the Kuramoto model [2], thus
providing an especially controllable system for the theoretical framework [3]. For
example the insertion of oscillators one by one [4] has been modelled in the context
of the Kuramoto model and has led to a generalization of the classical version [5].
The new version has different features, such as hysteretic behavior and first order
phase transition [6]. These features are also shared by another surprising system:
pedestrian walking on an oscillatory bridge [7], that mimics the effect observed in
the 2000 opening of the ―London Millennium Bridge‖. We have also found a
detailed analogy of Josephson junctions to another system of oscillators, the grid of
generators-machines that constitutes the utility power grid of the power electrical
system [8]. The main reason for the analogy is that energy flows from a generator
to an user if there is a phase difference between the corresponding rotators, see Fig.
1.
Figure. The schematic of the tri-phase connection of the generator G with the user U
over a line of maximum transmission capacity P MAX. In this scheme the rotators are
described by the phases .
Introducing a phase angle for each generator or machine, the power balance for the
simplest system of just one generator G and one user U in presence of inertia (I)
and dissipation (KD) reads [9] ( denotes the 50 Hz frequency and P the input
power):
K D   2 K D d G P MAX
d 2 G  P G


 G
 G sin  U   G .
 I G
G 
2
dt 2
I
I
dt
I 




(1)
That is formally equivalent to the basic equation for a Josephson junction if one
interprets in eq. (1) the phase angle as the superconducting phase and maps the
array of Josephson junctions over the Kuramoto model [2]. The energy flow
described by Eq. (1) can be generalized for many oscillators (machines and
50 Scientific Report 2005-2008
Transport properties in
superconducting materials
generators), leading to the problem of synchronization over a network [9].
However the utility grid has some special features that have not been yet
investigated. A realistic model should in fact include, at least, a bimodal
distribution of the natural frequencies and consider some realistic connection
topologies, not the global (all to all) connection that is more easily tractable. So an
accurate description of the power grid requires a combination of effects not yet
included in the Kuramoto model. Such a model description could be of interest also
for the proposed ―power grid‖ [11] that might connect very distant energy producer
and consumer, thus making the dynamic analysis of the full model unrealistic.
References
[1] S.H. Strogatz, Sync: The emerging Science of spontaneous Order (Hyperion, New York, 2003).
[2] K. Wiesenfeld, P. Colet, and S.H. Strogatz, Phys. Rev. Lett. 76, 404 (1996); M. Dhamala and K.
Wiensefeld, Phys. Lett. A 292, 269 (2002).
[3] J. A. Acebròn, , I.L. Bonilla, C. J. Perez Vicente, F. Ritrot, and R. Spigler, Rev. Mod. Phys. 77,
137 (2005).
[4] P. Barbara, A.B. Cawthorne, S.V. Shitov, and C.J. Lobb, Phys. Rev. Lett. 82, 1963 (1999).
[5] G. Filatrella, N.F. Pedersen, and K. Wiesenfeld, Phys. Rev. E 75, 017201 (2007).
[6] F. Giannuzzi, D. Marinazzo, G. Nardulli, M. Pellicoro, and S. Stramaglia, Phys. Rev. E 75,
051104 (2007).
[7] S.H. Strogatz, D.M. Abrams, A. McRobie, B. Eckhardt, and E. Ott, Nature (London) 438, 43
(2005).
[8] Prabha Kundur, Power system stability and control (McGraw Hill, 1993).
[9] G. Filatrella, A.H. Nielsen, and N.F. Pedersen, Eur. Phys. J. B 61, 485 (2008).
[10] R. Albert and A. Barabási, Rev. Mod. Phys. 74, 47 (2002).
[11] P. M. Grant, C. Starr and T. J. Overbye, Scientific American July, 78 (2006).
Scientific Report 2005-2008
51
Transport properties in
superconducting materials
Study of superconducting Nd1-xCexCuO4-δ thin films and single crystals
The present research activity focuses on the study of electron-doped high-Tc
superconductivity. The electron-doped materials have received so far a much lower
attention compared to the hole-doped ones. Several attempts have been made of
looking at the physics of electron-doped and hole-doped cuprates under a unifying
point of view, possibly elucidating
the general mechanism of high-Tc
superconductivity (SC). Nonetheless, some important differences characterize the
behaviour of these two classes of systems. The electron-doped ones exhibit a much
narrower SC phase and a much more robust antiferromagnetic (AF) phase
persisting above Tc up to optimal doping, with the two phases being adjacent to
each other. Their proximity in the phase diagram has made quite difficult the study
of the interplay between
them, and it is still under
debate whether long-range
AF
order
and
superconductivity
are
competing states[1] or
rather they coexist[2]. A
further open issue concerns
the symmetry of the
superconducting
order
parameter for which there
is no consensus on its
nature in these materials
[3—6]. Moreover, they
exhibit physical properties
which are very strongly
dependent
on
their
preparation.
For this
reason,
the
starting
point of
Cu 2/p/3/2 core level photoemission data for NCCO single
crystal and film by using hard X --rays.
the research activity in this
field
concerned
the
fabrication on the one hand of Nd1-xCexCuO4- (NCCO) thin films (prepared by
sputtering technique) and on the other hand of single crystals (prepared by floating
zone technique). At the SuperMat laboratories a special attention has been devoted
to the development of reliable experimental procedures allowing to efficiently
control the cerium doping level and the subsequent oxygen reduction process in
annealing atmosphere. The produced (not superconducting) thin films have been
characterized with photoemission spectroscopy[7]. Subsequently, a reliable way
has been devised of producing bulk sample targets from which high quality thin
films can be successfully realized[8]. The development of suitable targets, without
52 Scientific Report 2005-2008
Transport properties in
superconducting materials
elemental segregation, has been shown to improve the processing performance of
the target in sputtering chamber as well as the film uniformity. This achievement
has lead to the first NCCO superconducting thin films grown by d.c. sputtering
technique. The performed investigation has been particularly useful also in
tailoring the growth of NCCO single crystals by floating zone technique. Large
NCCO superconducting crystals are now available at the SuperMat laboratories. In
the next future, profiting both of the use of large scale facilities (various proposals
have been already accepted) and of the possibility to study, at the same time,
NCCO films and single crystals, we expect to give relevant contributions to the
issues still open in this topic. The analysis will also be accompanied by the
formulation of suitable phenomenological models able to describe the role played
by the oxygen reduction in the interplay between antiferromagnetism and
superconductivity [9].
References
[1] H.J. Kang et al., Nature (London) 423, 522 (2003).
[2] K. Yamada et al., Phys. Rev. Lett.90 137004 (2003).
[3] M.-S. Kim, J.A. Skinta, T.R. Lemberger, A. Tsukada, M. Naito, Phys. Rev. Lett.91 087001
(2003).
[4] H. Balci, V.N. Smolyaninova, P. Fournier, A. Biswas, R.L. Greene, Phys. Rev. B66 174510
(2002).
[5] A. Biswas et al., Phys. Rev. Lett. 88 207004 (2002).
[6] B. Chesca et al., Phys. Rev. B 71 104504 (2005).
[7] G. Panaccione, F. Offi, P. Torelli, G. Vanko, O. Tjernberg, P. Lacovig, A. Guarino, A.
Fondacaro, A. Nigro, M. Sacchi, N. B. Brookes, G. Monaco, Phys. Rev. B 77, 125133 (2008).
[8] S. Uthayakumar, R. Fittipaldi, A. Guarino, A. Vecchione, A. Romano, A. Nigro, H.-U.
Habermeier, S. Pace, Physica C 468 2271 (2008).
[9] J. Gauthier, S. Gagné, J. Renaud, M.-E. Gosselin, P. Fournier, P. Richard, Phys. Rev. B 75
024424 (2007).
Scientific Report 2005-2008
53
Transport properties in
superconducting materials
Non linear effects in the dynamics of Abrikosov vortices in type-II
superconducting films
In LTS linear vortex dynamics is a striking feature that reflects a linear voltagecurrent characteristics (VIC) above the superconducting critical current,
corresponding to the flux flow motion of the Abrikosov vortex lattice in type-II
superconductors [1]. In general the VIC curve is written V=R F (I-Ic), that for I>Ic
implies a linear behavior till the flux flow resistance RF and the critical current Ic
are current independent. In this case the usual picture given by Bardeen-Stephen
provides the well known flux flow resistance RF=RBS=(NФ0/Bc2) Rn, which
underlines that the total number of vortices N=B/Ф0 is moving with the same flux
flow velocity. On the other hand, non linearity can arise either in the flux flow
resistance or in the critical current distribution, in particular they both can display a
bias current dependence. In addition intrinsic electronic nonequilibrium phenomena
can be responsible of highly non linear behavior in LTS too [1]. The recent
advances in thin-film technology allow the fabrication of superconducting film
specimens with a strongly reduced thickness approaching the nm range. Due to the
corresponding strong increase in the surface-to-volume ratio, Joule heating effects
in the presence of an applied electric current can be reduced considerably, and
nonequilibrium processes can be studied more accurately. For the study of
electronic nonequilibrium effects in the mixed state of a type-II superconducting
film, in the past, it has been frequently used the Larkin and Ovchinnikov theory
(LO) [1]. It refers to the situation where the vortex lattice generated by an applied
magnetic field is set into motion due to the Lorentz force resulting from an applied
electric current. In the range not too far below the critical temperature TC , the
energy supplied in the core to the q.p by the electric field is sufficient to let them
escape from the core itself, determining a q.p. non equilibrium distribution. LO
derived the expression for the flux-flow resistivity which becomes electric-field
dependent. The resulting VIC shows an upward curvature, and negative differential
resistivity sets in at a critical vortex velocity vφ = vφ*. In the case of current-biased
operation, at the electric field F = F* the resistive voltage jumps discontinuously to
a higher value. The critical vortex velocity vφ* and the critical electric field F* are
related by means of the equation F* = B x vφ*, where B is the magnetic flux
density. Therefore the relation between the predicted critical vortex velocity and
the experimental critical voltage V* is given by vφ*(B)=V*/BL, where L is the
distance between the voltage contacts.
In addition to nonequilibrium effects, there are also non linearities of the VIC that
can be ascribed to a dynamical transition of the moving vortex lattice driven by the
increasing bias current. In fact the high velocity vortex motion is a consequence of
the competition between the elasticity of the vortex-vortex interaction and the
strength of the vortex-pin interaction. By varying the external magnetic field and
temperature, a tuning from the strong pinning to the weak pinning case can be
54 Scientific Report 2005-2008
Transport properties in
superconducting materials
obtained. Since the pinning force can also depend on the bias current, a dynamical
transition driven by an increasing bias current may occur from a disordered phase
with a higher Ic to an ordered one, marked by a lower Ic [2]. In the last years such
dynamical transition has been also related to the presence of a peak in the
differential resistance RF=dV/dI , which corresponds to the change in the vortex
motion from a plastically disordered flow to a more ordered elastic motion, i.e.
dynamic ordering [3,4]. In our recent works we report on the observed non linear
effects of the vortex motion in superconducting thin Nb films at high electric
driving currents [5-7]. The critical vortex velocity vφ* which could be ascribed to
the flux-flow instability, as predicted by LO, was measured as a function of the
magnetic field and temperature. In addition, in the quite strong flux pinning Nb
superconducting films, a peak in the electric current dependence of the differential
flux-flow resistance was observed before the instability was reached. As a result, a
dynamic ordering transition can occur in the instability regime of the vortex lattice.
To our knowledge, this is the first time that such a non linear effect was observed
close to the vortex velocity instability.
REFERENCES
[1] R. P. Huebener, Magnetic Flux Structures in Superconductors, 2nd edition, Springer, Berlin
2001
[2] X. B. Xu, H. Fangohr, X. N. Xu, M. Gu, Z. H. Wang, S. M. Ji, S. Y. Ding, D. Q. Shi, and S. X.
Dhou, Phys. Rev. Lett. 101, 147002 (2008)
[3] A. E. Koshelev and V. M. Vinokur, Phys. Rev. Lett. 73, 3580 (1994)
[4] J. M. E. Geers, C. Attanasio, M. B. S. Hesselberth, J. Aarts, P. H. Kes, Phys. Rev. B 63, 094511
(2001)
[5] G. Grimaldi, A. Leo, A. Nigro, S. Pace, A. A. Angrisani, and C. Attanasio, Jour. Phys. C. S. 97,
012111 (2008)
[6] G. Grimaldi, A. Leo, A. Nigro, S. Pace, C. Cirillo, and C. Attanasio, Physica C 468, 765 (2008)
[7] G. Grimaldi, A. Leo, C. Cirillo, C. Attanasio, A. Nigro, and S. Pace, to be published on Jour.
Phys. C. M.
Scientific Report 2005-2008
55
Transport properties in
superconducting materials
Thin Nb films deposited on porous substrates
Recently a new research line focuses on superconducting properties of Nb thin
films sputtered on different PS substrates obtained by electrochemical etching
of Si in a HF solution [1,2,3]. The control of the etching parameter allows to
obtain templates with pores diameter (d) and interpore distance (a) tunable in
the range 5-10 nm and 10-40 nm, respectively. The characteristic pore features
of these PS substrates are, to our knowledge, the smallest used in
superconducting field at this purpose. These templates were used as a systems
of pinning arrays in order to obtain the formation of commensurate vortex
structures at high matching fields down to low temperatures. Critical
temperatures and perpendicular upper critical fields measurements were
performed on these films. Anomalies in the Hc2(T) behavior, as well as in the
field dependence of the R(T) width, were in fact observed at H  1 Tesla, which
was estimated as the first matching field H1. This value is larger than typical
matching fields of periodic pinning arrays obtained both by lithographic
techniques and by using self-organized Al2O3 templates.
These preliminary results are promising, specially considering that PS prepared
by traditional electrochemical etching exhibits a sponge structure, so that the
holes are not a regularly distributed ordered planar pinning structure. Future
work will focus on critical currents density studies, carried out both by
transport measurements on patterned samples and by magnetization
measurements. Moreover, due to the extreme reduced features size of PS
templates, these systems look appealing also for the studying of twodimensional superconducting wire networks.
Figure. FESEM image (500000X)
of the top of a porous Si substrate
(d=10 nm, a=20 nm) covered with
a conductive PdAu layer, 8 nm
thick [2]
References
[1] O. Bisi, S. Ossicini, and L. Pavesi, Surf. Sci. Rep. 38, 1 (2000)
[2] S. K. Lazarouk, et al., Physics, Chemistry and Application of Nanostructures. Nanomeeting
2007 (Minsk, Bielorussia), World Scientific, Singapore, 2007
[3] M. Trezza, S.L. Prischepa, C. Cirillo, R. Fittipaldi, et al., and C. Attanasio, J. Appl. Phys.
104, 83917 (2008)
56 Scientific Report 2005-2008
Transport properties in
superconducting materials
Tunneling Spectroscopy on Superconducting Materials

Study of the Superconducting properties of the two-band superconductor MgB2.
The existence of two distinct superconducting energy gaps in the simple binary
compound MgB2 with a relatively high TC of 40 K offers a unique opportunity to
study the electrodynamics of a multigap superconductor. The effects of inter-band
coupling and scattering on the superconducting order parameter and TC were
discussed since long time ago, but only after the discovery of superconductivity in
magnesium diboride there has been a real opportunity to experimentally study the
phenomenon.
Scanning tunneling spectroscopy (STS) appears as the major tool with its high
spatial and energy resolution to realize a direct study the magnitude, the symmetry,
and the angular dependence of the superconducting gap in this material. Indeed,
tunneling spectroscopy (TS) probes directly the superconducting Density of States
(DOS), with an energy resolution of a few kT.
Using Scanning Tunneling Microscope at low temperature we can explore the
superconducting phase diagram in the π-band of the two-band superconductor
MgB2. In this band the peculiar shape of the local tunneling spectra and their
dynamics in the magnetic field reveal the complex character of the quasiparticle
density of states. The gap in the DOS is first rapidly filled with states in raising the
magnetic field up to 0.5 T and then slowly approaches the normal state value: the
gap is observed up to 2 T. Such a change in the DOS dynamics suggests the
existence of two terms in the DOS of the π-band: a first one, reflecting an intrinsic
superconductivity in the band and a second one, originating from an inter-band
coupling to the σ-band. These two terms behave differently in the magnetic field,
the first term almost vanishing in the field of 0.6 T.
Moreover, the presence of two bands with distinct superconducting gaps leads to
several unusual properties, such as the temperature- and field-dependent
anisotropy, which dominate the magnetic and transport properties. Anisotropy is
related to the intraband and interband electron scattering that can be modified by
partial chemical substitutions. In particular, aluminium (replacing magnesium) and
carbon (replacing boron) have successfully entered in the MgB2 structure, doping
the material with additional electrons. Al doping can realize a considerable out-ofplane distortion of the B atoms causing a significant increase of the interband
scattering.
We then performed local spectroscopy on high quality Mg1-xAlxB2 single crystals
by means of variable temperature scanning tunneling spectroscopy in magnetic
field up to 3 Tesla. Single gap conductance spectra due to c-axis tunneling were
extensively measured, probing different amplitudes of the three-dimensional  as
a function of Al content (i.e. as a function of the critical temperature TC).
Scientific Report 2005-2008
57
Transport properties in
superconducting materials
Temperature and magnetic field dependences of the conductance spectra were
studied in S–I–N configuration: the effect of the doping resulted in a monotonous
reduction of the locally measured TC down to 24 K for x = 0.2. We have got clear
evidence that the locally measured energy gap, as well as the upper critical field,
reach maximum values =2.4 meV and Hc2=3 T around x=0.1 (TC=33 K)
regardless of the monotonous fall of TC as a function of doping.
(a)  and (b)  /KBTC as functions of TC ( ) compared with data already reported in the
literature. F. Giubileo, F. Bobba, A. Scarfato, and A. M. Cucolo et al., PHYSICAL REVIEW B 76,
024507 (2007). (c) Magnetic field dependence of the p-band energy gap. A. Kohen, F. Giubileo, et
al., Eur. Phys. J. B 57, 21–25 (2007), and F. Giubileo et al., PHYSICAL REVIEW B 76, 024507
(2007)
The magnetic field dependence was studied in a local way: an estimation for upper
critical field Hc2 was inferred from the evolution of the tunneling spectra with the
field perpendicular to the sample surface, for different doping levels. The high
spatial resolution of the STS technique allowed us to evidence possible nonhomogeneities of the superconducting properties on the sample surface with
variation of in the same sample depending on different local levels of doping. The
locally measured upper critical field resulted to vary for different dopings, and the
maximum value Hc2=3 T was found for samples with TC=33 K. The evolution of
the density of states (DOS) was found to be characterized by two distinct regimes
separated by a crossover region. Our results indicate a rapid suppression of the
intrinsic term in -band superconductivity for 0 T < B < 0.5 T. At high fields (0.8 T
< B < 3 T) the superconductivity in the -band survives uniquely due to the
coupling to the r-band. The shape of tunneling spectra suggests an important role
played by the quasiparticle inter-band scattering.
58 Scientific Report 2005-2008
Transport properties in
superconducting materials

Pairing State in unconventional superconductors by Point-Contact Andreev
Reflection Spectroscopy
Point contact spectroscopy is a versatile technique widely used to study the basic
properties of superconductors, such as the density of states at the Fermi level and the
superconducting energy gap. The technique consists in establishing a contact between a tip
of a normal metal (N) and a superconducting sample (S), thus forming a small contact area
that is a ―point contact‖ junction. By varying the distance and/or the pressure between tip
and sample it is possible to obtain different regimes. Indeed, quasiparticle tunnel
spectroscopy is obtained for high barriers, while point contact Andreev reflection
spectroscopy is achieved in case of low barriers. Andreev reflections take place at the N/S
interface when an electron, propagating in the normal metal with an energy lower than the
superconducting energy gap, enters in the superconductor forming an electron pair (Cooper
pair) while a hole, with opposite momentum with respect to the incident electron, is
reflected in the normal metal. A single reflection corresponds to a net charge transfer of 2e,
where e is the electron charge, from the normal metal to the superconductor. In the limit of
low barriers at low temperatures, all the incident electrons at the N/S interface with energy
eV< (with  energy gap of the superconductor) are Andreev reflected and the
conductance doubles the normal states value. This phenomenon has been theoretically and
experimentally studied by Blonder, Tinkham, and Klapwijk (BTK theory) within a
generalized semiconductor model using the Bogoliubov equations to treat the transmission
and reflection of quasiparticles at the interface.
Figura 1. The dI /dV vs V characteristics
measured in different Ru-1212/Pt–Ir PC
junctions at 4.2 K. The experimental data
(dots) are shown together with the best
theoretical fittings (solid lines) obtained by a
modified BTK model for a d-wave symmetry
of the superconducting order parameter.
Samanta Piano, Fabrizio Bobba, Filippo
Giubileo, Anna Maria Cucolo, Marcello
Gombos, and Antonio Vecchione,
PHYSICAL REVIEW B 73, 064514 (2006)
We have analyzed the PCAR conductance spectra obtained in superconducting
RuSr2GdCu2O8 (Ru-1212) polycrystalline pellets. All the conductance curves at low
temperatures show a zero bias conductance peak that decreases for increasing temperatures
and disappears at the local critical temperature Tc=30 K of the superconducting grain in
Scientific Report 2005-2008
59
Transport properties in
superconducting materials
contact with the Pt–Ir tip. The triangular shape of all the measured spectra has been
modeled by using a modified BTK model for a d-wave symmetry of the superconducting
order parameter. This finding suggests a closer similarity of the Ru-1212 system to the
high TCcuprate superconductors rather than to the magnetic ruthenate Sr2RuO4 compound.
However, the remarkably low values of the energy gap  =(2.8±0.2) meV and of the ratio
2/kBTC=2 indicate major differences between the Ru-1212 and the high TC cuprates. We
speculate that the presence of ferromagnetic order within the superconducting phase results
in an effective reduction of the energy gap. We have also demonstrated that, when dealing
with granular samples, intergrain coupling effects can play a predominant role. In some
cases, an intergrain Josephson junction in series with the point contact junction is formed.
Taking into account this feature as well, all conductance spectra have been properly
modeled by considering a d-wave symmetry of the order parameter, with consistent values
of the amplitude of the energy gap. By fixing all the fitting parameters to their values at the
lowest measured temperature, and by varying , the temperature dependence of the energy
gap has been extracted from the conductance characteristics of a very stable junction.
We have also performed point-contact spectroscopy experiments on superconducting
micro-constrictions between Nb tips and high quality MgB2 pellets. The conductance as a
function of bias measured above the Nb critical temperature reveals that an intergrain
MgB2/MgB2 junction is often formed in series with the MgB2/Nb contact. This results from
a small piece of MgB2 remaining on the tip apex when relieved from the pellet. Depending
on the tip pressure the MgB2 /MgB2 contact resistance can be either larger (tip far from the
pellet) or comparable (tip into the pellet) with the MgB2 /Nb point-contact resistance. In
the last case, an accurate theoretical analysis has to be carried out to extract the correct
value of the MgB2 superconducting energy gap. For T<TC of Nb, we have observed the
Josephson effect as well as subgap resonances. We explain these features in terms of
subharmonic gap structures due to multiple Andreev reflections. From the analysis of the
SGS, consistently with the values measured for T>TC of Nb, we have extracted the correct
temperature dependence of the Nb energy gap and the value 2.4 meV for the 3D energy
gap at the MgB2 Fermi surface. In our junctions, at T =4.5 K, we have measured ICRN
values up to 2.2 meV, among the highest reported in the literature. The temperature
dependence of the ICRN product follows the classical Ambegaokar-Baratoff behavior. Both
observations completely confirm the results predicted by a recent theoretical model. In
addition to this, the simultaneous observation of both Josephson current and SGS’s
unambiguously indicates the coupling of the Nb energy gap with the MgB2 3D band.
Figure 2. Conductance characteristics
measured for T < TC of Nb (scattered
graph) and for T > T C of Nb (solid line).
Arrows indicate the energy positions of
subharmonic gap structures appearing in the
S–c–S’ configuration. Inset: Temperature
evolution of the SGS.
F. Giubileo, M. Aprili, F. Bobba, S. Piano,
A. Scarfato and A. M. Cucolo, PHYSICAL
REVIEW B 72, 174518 (2005).
60 Scientific Report 2005-2008
Transport properties in
superconducting materials
Tunneling spectroscopy on high Tc cuprates
Among high-Tc superconductors (HTS), Bi2Sr2CaCu2O8+ (Bi-2212) is one of the
most extensively studied by means of tunneling spectroscopy and other surfacesensitive experiments. While the issue of pairing symmetry in HTS is not entirely
settled, there is a certainly considerable evidence to suggest that the order
parameter has d-wave symmetry, instead of the s-wave symmetry of conventional
superconductors. Clear tunneling gap features are generally found on Bi-2212, with
a great deal of reproducibility among tunneling spectra not only in the size of the
energy gap but in the overall spectral shape. The high-bias dip feature appears at
2 in superconductor-insulator-normal metal (SIN) junctions, while in
superconductor-insulator-superconductor (SIS) junctions it is reproducibly found to
be at 2+. In our work,  has been obtained by fitting quantitatively the Bi-2212
tunneling spectra with the Eliashberg strong-coupling theory extended to a d-wave
symmetry gap function. This reproduces the shape, location and strength of the dip
feature as well as the measured gap value. Thus it appears that the dip feature can
be considered a strong coupling effect analogous to phonon structures of
conventional superconductors. Although there have been numerous articles
discussing the origin of the tunneling gap feature, this work is the first quantitative
fit of a complete experimental tunneling DOS using a self-consistent, d-wave,
Eliashberg formalism. We have combined a normal-state conductance, accounting
for band structures effects as well as a possible pseudogap, with a pure
superconducting state conductance [1]. The theoretical model used to fit point
contact tunneling data at high biases, i.e. in the normal state region, contains an
effective band structure for the CuO2 planes extracted from angle-resolved
photoemission spectroscopy (ARPES) for Bi-2212. On the other hand, the
superconducting density of states has been obtained from a model with a d-wave
symmetry of the order parameter. The results show that the dip-hump feature
observed in the experimental data cannot be attributed to a normal state effect.
Instead this structure can arise from state-conserving deviations in the
superconducting density of states.
References
[1] P. Romano, L. Ozyuzer, Z. Yusof , C. Kurter, J.F. Zasadzinski (2006), Modeling study of the
dip-hump feature in Bi2Sr2CaCu2O8
, Phys. Rev. B 73, 092514.
Scientific Report 2005-2008
61
Transport properties in
superconducting materials
62 Scientific Report 2005-2008
Other Activities
Other activities

Superconducting Single Photon Detectors
This research project has been oriented to the investigation of optical detectors with
advanced performances. More specifically, radiation detectors based on
superconductive materials are investigated. The use of superconductors allows to
reach elevated sensitivity (up to single photons) and very fast response time (up to
few ps). The“standard” Nb and NbN have been used to develop a fabrication
technology that could allow the realization of innovative detectors based on ultra
thin superconductive striplines called Superconductive Single Photon Detectors
(SSPD).
The SSPDs sensing mechanism is based on the combination of the submicrometric
width of a stripe (about 100 nm) and the transport properties of the
superconducting film. Due to the biasing point and the low impedance of the
electromagnetic environment in which the device is embedded, as soon as a single
photon is adsorbed in the stripe, in a time of the order of 10 ps a normal “hot spot”
is created and successively a voltage pulse is generated when the whole section of
the film becomes normal. SSPDs are normally realized with ultra-thin
superconducting films patterned in a meander shape with sub micrometer wide
strips. The meander geometry is used to enhance the filling factor of the detection
area and hence the detection efficiency of the device. However the meander
geometry implies a large total device inductance, which negatively affects the
generated pulse timing. Recently an alternative geometrical nano-wire
configuration (a parallel array instead of a meander shape) has been proposed to
enhance both speed and signal amplitude of single photon detectors. The device is
normally biased near its critical current, which is much larger of that of a single
nano-wire. Then, the photon-induced transition of one of the wires in the parallel
array induces a transition of all the other wires with a cascade mechanism. When
all the wires have switched to the normal state, the detector becomes highly
resistive and the total bias current redistributes to the external load.
More recently a novel superconducting three-terminal device, also based on
superconducting nanowires, has been designed and realized. The device is capable
of fast pulse discrimination/amplification and can find application as cryogenic
front-end to superconducting detectors and digital circuits. Extensive experimental
characterization is in progress.
References
[1] O. Quaranta, S. Marchetti, N. Martucciello, S. Pagano, M. Ejrnaes, R. Cristiano, C. Nappi,
“Superconductive three-terminal amplifier or discriminator”, to be published in IEEE Transaction
on Applied Superconductivity (Applied Superconductivity Conference 2008)
Scientific Report 2005-2008
63
Other Activities

Transport properties of organic materials
This recent activity deals with the DNA electrical properties, an emerging new
research field that includes distinct scientific areas, making it one of the most
interesting interdisciplinary topics. DNA is in fact attracting increasing interest in
the scientific community, especially as a material to be potentially applied to
nanometric molecular electronic devices. Despite the wealth of data from
experimental and theoretical work, the question whether DNA is or not a conductor
and how such a complex physical system can be modelled remains unsettled. Our
transport measurements on differently shaped DNA show that, regardless the shape
and the length of the molecules, conductivity is due to the contribution of shortrange transport inside the molecule that originates from transmission through the
energy barrier between base pairs and long-range hopping through the ensemble of
molecules. A step-like feature is observed in the I-V curves, and our hypothesis is
that it represents an intrinsic characteristic of the molecules under investigation [1].
A phenomenological model has been developed and the computer-generated curves
show that the step-like feature appears more pronounced when the transmission
channel is stronger due to the simultaneous contributions of more molecules. Its
voltage position may be characteristic of the HOMO-LUMO energy gap inside the
molecule.
References
[1] P. Romano, A. Polcari, B. Verruso, V. Colantuoni, W. Saldarriaga, E. Baca (2007), Nonlinear
current-voltage characteristics measured across circular deoxyribonucleic acid (DNA) molecule
bundles, J. Appl. Phys. 102, 103720.
64 Scientific Report 2005-2008
Other Activities

Local field emission properties of partially aligned multiwalled carbon-nanotubes by
Atomic Force Microscopy
Since their discovery, carbon nanotubes have attracted a considerable attention due
to their peculiar and unsurpassable chemical, mechanical and electronic properties.
In particular, their electronic transport behaviour (metallic versus semiconducting
like) may vary according to their structural conformation, thus suggesting the use
of single walled (SWNTs) or multiwalled (MWNTs) carbon nanotubes as
conducting nanowires suitable for the investigation of the electric transport
phenomena in the mesoscopic regime. Within this context, due to the possibility of
tuning their physical properties via a proper modification of the growing conditions
(techniques and/or growing parameters), nanotubes represent ideal candidates for
the development of a new class of carbon-based electronic nanodevices. In
particular, individual field emitters, which give currents with low energy spread
that are spatially collimated, can usefully be exploited in electro-beam imaging
tools, in high resolution displays and in x-ray tubes. Furthermore, the use of carbon
nanotubes as field electron emitters is considered as one of the most promising
technological applications due to the possibility of industrial production. Indeed,
carbon nanotubes are characterized by peculiar field emission properties due to
their good electron conductivity and a specific geometry, resulting in a drastic
amplification of the electrical field strength in the vicinity of the nanotube tip.
Figure. (Top) AFM probe used as counterelectrode for the measurement of the FE
current from a vertically aligned array of
MWCNTs. The whole apparatus consists of
a vacuum chamber hosting an AFM/STM
connected to an external
source
measurement unit. (Bottom) Predicted FE
current from area having radius r, and
considering the electric field magnitude
distribution generated by a metallic conical
tip (30° aperture, 25 m height) on a flat
graphite film. Tip-film potential difference
150 V, distance d = 500 nm.
A. Di Bartolomeo, A. Scarfato, F. Giubileo,
et al., CARBON 45 (2007) 2957–2971 and
F. Giubileo, A. Di Bartolomeo et al.,
CARBON 47(2009) 1074-1080.
Atomic force microscopy (AFM) was used to study the field emission (FE)
properties of a dense array of long and vertically quasialigned multi-walled carbon
nanotubes .The use of nanometric probes enables local FE measurements. The
micrometric inter-electrode distance allows to achieve high electric fields with a
modest voltage (up to 250 V/m) and attain current densities larger than 105
Scientific Report 2005-2008
65
Other Activities
A/cm2. FE behaviour is analyzed in the framework of the Fowler–Nordheim
theory. A field enhancement factor of 40–50 and a turn-on field of 15 V/m at an
inter-electrode distance of 1 µm are estimated.
The high spatial resolution provided by the AFM allowed precise estimation of the
tip-sample distance in the submicron region. The dimension of the probe (curvature
below 50nm) allowed to measure current contribution from sample areas as small
as 1m2. The study of long-term stability of the field emission current evidenced
that on these small areas the field emission current remains stable (within 10%
fluctuations) several hours (72 hours) also at different current intensities between
10-5A and 10-8A.
We also realized in situ FE characterisation of an individual MWCNT by means of
a nanomanipulation system operating inside a SEM, ensuring an high control
degree on the field emission geometric parameter. An individual MWNT has been
attached onto the cathode tip and current measurement have been carried out with
an applied voltage varying from 0 to 120 V. The emitted current has been measured
with a sensitivity of ~ 10 fA.
Figure. (a) SEM image representing the geometry
of the field emission experiment, performed on a
suspendedMWNT. A magnified SEM image of
the MWNT apical structure is reported as the
inset. (b) SEM image of the field emission
geometry after a prolonged electron beam
exposure of the tip region (reported as the inset).
(c) I–V characteristic of the MWNT before
(white square) and after (black circle) the
electron beam exposure.
M. Passacantando, F. Bussolotti, S. Santucci, A.
Di Bartolomeo, F. Giubileo, L. Iemmo, A. M.
Cucolo, Nanotechnology 19 (2008) 395701 (6p
To complete the FE characterization of single MWNTs, we also investigated the
innovative capability to perturb (switching off) the emission process by modifying
the tube apex by electron beam irradiation. To this aim, a 10 keV electron beam
was focused on the MWNT terminating region (80 nm ×80 nm of irradiation area).
After 10 min of exposure a clear morphological modification was observed, with
an overall smoothing of the initially sharp, open-ended MWNT apical region
resulting, at the same time, in a complete suppression of the field emission
currents, as reported in figure, in the case of exposed MWNTs, corresponding to
higher voltage value.
66 Scientific Report 2005-2008
In this paragraph we briefly summarize the main experimental facilieties available
at SUPERMAT:
Main equipments:
Fabrication



Characterization







Thin films
o DC Multi-cathode Sputtering Systems
o Routable DC Sputtering System
o UHV diode sputtering
o UHV electron beam evaporator
Thick Films
o Sputtering deposition system for YBa2Cu3O7-δ
thick films on large areas
Single Crystals
o Mirror furnace for floating zone crystal growth
Scanning Probe Microscopy
o Cryogenic SFM
o Multi-mode UHV Scanning Probe Microscope
o Room Temperature Multimode–Nanoscope V
High-resolution three circles and low-angles X-Ray
Diffractometer
Scanning Electron Microscope equipped with EDS, WDS
and EBSD analyses
AC magnetic susceptibility systems, PPMS system,
16 T Vibrating Sample Magnetometer (VSM)
DTA/TGA equipped with mass spectrometer
Differential scanning calorimeter
Electron Beam Litography
Fabrication
Thin films fabrication
The sputtering deposition technique uses the effect of an electric field between two
electrodes in a vacuum chamber to extract atoms from a cathode and deposit them
on a specific substrate, located on the anode, through the use of a controlled
plasma. In the case of High Temperature SuperConducting (HTSC) films, this
process must occur with a DC electric field in presence of an O2 plasma and at high
temperatures of the substrate, subsequently followed by an annealing in a high
pressure of O2, in order to allow the right phase formation.
 Dc Multi-chatode Sputtering systems
DC multi-chatode sputtering systems are used
for deposition of perovskite thin films and
multilayers of high Tc superconducting
materials like YBa2Cu3O7-δ, BSSCO, and
magnetic materials as LCMO. A controllable
heater is installed in the chamber to permit
deposition at high temperature up to 900°C.
The system is equipped of an arm provided of
translation motion on which are accommodated
three targets of different materials. This equipment of the sputtering system is very
suitable to deposit hetero-structure in situ and it permit the realization of bilayer
and trilayer of superconducting and magnetoresistive materials.
 Routable Dc Sputtering deposition system
The dc sputter deposition system shown in the figure has been designed for
research involving high temperature superconducting compounds and devices
based on these materials. In particular this system has been successfully used to
fabricate thin films of the Nd2-xCexCuO4-d compound. This sputtering system is
provided of: a routable flange with three sputter sources, a substrate heater that can
reach temperatures up to 900 °C, and a fully automated system control in order to
achieve high reproducible level of the deposition processes.
A homemade software in LabVIEW language has been developed to run the
control system by allowing: the automated starting and stopping of the deposition
process by rising and lowering the plasma current at a desired rate; the starting of a
feedback bias system of the temperature controller for the substrate heater; the
rotation of the flange and the setting of the hold time of each source in the
sputtering position; and the sputtering time for all the three targets allowing the in
situ deposition of multilayers with the desired numbers of layers and thickness of
the single layer, so a multilayer sample may consist by three different materials.
Scientific Report 2005-2008
71
Fabrication
The software allow the monitoring and saving of the values of the sputtering
parameters during the whole process: total pressure in the chamber; plasma current;
plasma voltage; and substrate temperature.
 UHV diode sputtering
The system features a metal sealed UHV design and is equipped with a load lock
chamber, to keep the main sputter one at a constant pressure in the 10-9 mbar range.
At the moment three 2” source diode magnetron system are present. The Angstrom
Science magnetrons delivers a minimum guaranteed ± 3% thickness uniformity
over 2’’ at 10 – 15 cm source-substrate distance for any material due to a special
patented profiled magnets. The system is designed to perform thin film depositions
at a controllable substrate temperature, monitored by a thermocouple, and at an
adjustable substrate Z positon. A specially designed computer controlled movable
shutter makes possible to grow of up to 9 samples with different thickness in the
same deposition run. The vacuum is provided by a rotary and a turbomolecular
pumps for each chamber. Five pressure gauges monitor the foreline, the base and
the Ar process pressures. The thin film deposition growth is monitored by a quartz
crystal monitor calibrated by low-angle x-ray reflectivity measurements.
(a)
(b)
(a) UHV diode sputtering system; (b) particular of Nb deposition
 Electron beam evaporator
This system is an high vacuum evaporator for any
material in the temperature range of 400K to 3100K.
An integrated flux monitor allows maximum
deposition control. Highly efficient watercooling
ensures negligible outgassing during operation. It can
accommodate four crucibles at a time to allow
multiple and sequential evaporations.
72 Scientific Report 2005-2008
Fabrication
Thick films fabrication
 Sputtering deposition system for YBa2Cu3O7-δ thick films on large areas
The DC sputtering deposition system for (HTSC) thick films is a facility planned to
realize highly uniform and high areas YBa2Cu3O7-δ layers in an O2 atmosphere. It
consists into three main parts:
 the sputtering chamber, where the deposition occurs
 the vacuum line, with all the components to evacuate the chamber
 a control panel, where the various parameters of the deposition process can
be controlled
The sputtering chamber is made by a cylindrical steel
structure, inside which a semicylindrical copper screen is
located upside, and a heater is placed downside the
chamber. The YBa2Cu3O7-δ target is located inside the
screen and act as a cathode, while the heater, over which
the substrates are placed, is connected at the anode polarity.
Two high power infrared lamps inside it permits to reach
the high temperatures needed for the correct YBa2Cu3O7-δ
phase formation during the deposition
The vacuum line is composed by a two stage apparatus,
with a membrane pump for a preliminary vacuum and a
turbomolecular pump, directly connected to the chamber
through a gate; this permits to reach a base pressure pbase ≈ 10-6 mbar.
The control panel contains, besides the main power of all the system, a section
where two mass flow controllers can precisely dispense the gas inlet into the
chamber, the heater section with the control of the current to the lamps and the
temperature reading, linked to a thermocouple close to the heater, the DC power
supply section and the vacuum control section, with a multigauge instrument and
an electronic control of the pumps. The film deposition occurs by inserting O2 in
the chamber at a pressure p ≈ 1-2 mbar and at a substrate temperature T ≈ 800°C,
with typical electrical power density values W ≈ 10 W/cm2. A post-annealing at
high pressure O2 atmosphere performed at ≈ 500°C allows the formation of the
right superconducting phase.
Scientific Report 2005-2008
73
Fabrication
Single Crystals Fabrication
 Infra red image furnace
For the study of physics and chemistry of
condensed phases, it is crucial to obtain
good quality single crystals of material
concerned, since for polycrystalline
materials, the properties of the grain
boundaries often manifest themselves
stronger than the properties of the
materials itself. The crystal growth
programme at SuperMat was established
in 2003 and it is a consequence of a large
experience
on
the
synthesis
of
superconducting and magnetic oxides
Fig.1. Two mirror furnace for floating zone
crystal growth
acquired in the last twenty years. The
main equipment related to the single
crystal growth activity is the infra
red image furnace installed in 2005
(see Fig.1). This was the first time an
instrument of this kind was used in
Fig. 2. An example of strontium ruthenate crystal
Italy. It is a two mirror system,
grown by the floating zone method.
(model
SC1MDH1102),
manufactured by NEC Machinery in Japan equipped with video monitoring and pc
acquisition and control system. Light from the two halogen bulbs is focused by the
semi-ellipsoidal mirrors onto a central zone. In
this case the mirrors are gold coated water
cooled aluminum blocks. Temperatures of up to
2050 degrees centigrade can be achieved in this
system. The two counter rotating shafts are used
to support the polycrystalline feed rod (upper
shaft) and the single crystal/seed rod (lower
shaft). A molten zone is established between
these two solid rods. The liquid forming the
molten zone is held in place by surface tension.
The rotation of the shafts helps to stabilize and
trap the melt, mix the constituents to
homogenize the sample and also produces a
more uniform heating of the molten material. Fig.3. Example of eutectic
The feed and seed rods are slowly moved crystal of Sr2RuO4/Sr3Ru2O7.
74 Scientific Report 2005-2008
Fabrication
downwards (growth rates vary between 0.5 and 50 mm/hour). New material is
introduced into the molten zone from the feed rod and deposited in the form of a
single crystal onto the seed rod. The growths take place inside a quartz tube. This
can be over pressured with up to 10 atmospheres of a gas that can be selected to
suite the materials being prepared. Choices include a reducing atmosphere such as
an argon/hydrogen mixture, an inert gas such as argon or nitrogen, or an oxidising
atmosphere of air or oxygen. Sample boules of up to 80 mm in length and 8 mm in
diameter can be grown. Single crystals are extracted and prepared for further
studies using a range of crystal cutting and polishing tools. The efforts of the
researchers involved in the field of single crystal growth are focused on the growth
of large superconducting and magnetic oxides (see Fig.2). Single crystals of high
Tc superconducting oxides and pure and eutectic strontium ruthenates (Fig.3) are
regularly produced and made available to collaborators within the Italy and abroad.
Scientific Report 2005-2008
75
Fabrication
76 Scientific Report 2005-2008
Characterization
Scanning Probe Microscopy
 The Cryogenic SFM
The Cryogenic SFM is a dedicated instrument for operation at cryogenic
temperatures from 6 K to 300 K and in high magnetic fields up to 7 T and extends
the range of low temperature UHV SPM applications to the investigation of
insulators and magnetism. It features a completely non-magnetic design, UHV
compatibility, 3D-sample/probe positioning, and in-vacuum sample and
cantilever/tip exchange. Beside STM, the integrated interferometric force detection
enables full AFM capabilities (contact/non-contact mode) in various specialised
modes such as Magnetic Force Microscopy (MFM). The scanning tunneling
microscope (STM) is widely used in both industrial and fundamental research to
obtain atomic-scale images of metal surfaces. It provides a three-dimensional
profile of the surface which is very useful for characterizing surface roughness,
observing surface defects, and determining the size and conformation of molecules
and aggregates on the surface.
The STM is a non-optical microscope which employs principles of quantum
mechanics. An atomically sharp probe (the tip) is moved over the surface of the
material under study, and a voltage is applied between probe and the surface.
Depending on the voltage electrons will "tunnel" (this is a quantum-mechanical
effect) or jump from the tip to the surface (or vice-versa depending on the polarity),
resulting in a weak electric current. The size of this current is exponentially
dependent on the distance between probe and the surface. Obviously, for a current
to occur the substrate being scanned must be conductive. By scanning the tip over
the surface and measuring the height (which is directly related to the voltage
applied to the piezo element), one can thus reconstruct the surface structure of the
material under study. High-quality STMs can reach sufficient resolution to show
single atoms. STM is also a tool for modification of surfaces through various
methods such as indenting the tip or modification of the substrate by the electrons
Scientific Report 2005-2008
77
Characterization
emitted from the tip. In the atomic force microscope (AFM) the tip as used in STM
is replaced by a flexible cantilever. The cantilever is equipped with a sharp tip at
one of its ends and the cantilever is scanned across the interface. Due to the
topography of the probed sample and/or due to attractive or repulsive forces
between the sample surface and the tip, the cantilever is bent up and down during
scanning. The bending motion of the cantilever is detected by a laser beam
reflected from the cantilever to a position-sensitive light detector.
Fields of Applications: Investigation of the Local Density of States (LDOS) by
tunneling spectroscopy; Vibrational spectroscopy (inelastic, IETS); Magnetism &
Magnetic structures: domain size, domain reorganisation, field dependence of
domains; Superconductivity: vortices, vortex pinning, vortex pattern.
 Multi-mode UHV Scanning Probe Microscope (STM/AFM)
The combined UHV AFM/STM is an
extraordinarily versatile scanning probe
microscope for all types of samples, ranging
from non-conducting to conducting, and
from hard to delicate soft surfaces. It
combines various STM and AFM
measurement modes including contact mode
AFM with simultaneous lateral force
(friction) detection and non-contact mode
AFM in a single instrument. In addition, the
AFM/STM offers the unique capability of multi-mode measurements, i.e.
simultaneous acquisition of several AFM and STM related signals such as
tunneling current, force, and force gradient in a single image. AFM detection is
based on optical beam deflection. This detection method offers unsurpassed force
sensitivity and allows high resolution imaging in contact mode with very low
forces down to the 10-11 N range. The instrument accepts both STM tips and all
commercially available cantilevers. An invacuum I/V converter ensures optimal STM
performance. STM can be performed either
by using dedicated STM tips or conductive
cantilevers;
the
latter
even
allows
simultaneous AFM and STM measurements
to be performed. All operational modes are
supported by OMICRON's proprietary
SCALA SPM control system, which offers
state-of-theart data acquisition and image
processing.
Schematic setup of the UHV
STM/AFM
78 Scientific Report 2005-2008
Characterization
 Room Temperature Multimode SPM Nanoscope V
The Multimode AFM with the Nanoscope V controller provides a variety of high
resolution surface imaging techniques including contact mode AFM, tapping
mode AFM and Scanning Tunneling (STM/AFM). Resolution is sub-nm for
height-measurement capability while lateral (x-y) resolution is tip dependent ,
generally on the order of
the tenth of
nanometers.
The system is fully computer controlled with a
scan piezo linearization technology, which
delivers a calibrated, non-linear waveform to the
piezoelectric scanner achieving a linear motion
output for all scan sizes, scan rates and scan
rotations. It has the capability to perform thermal
tuning of the cantilever by sampling frequencies
up to 2 MHz and generally it provides three
independent digital to analog converters (DACs)
per axis (x,y and z). The Nanoscope V controller
is provided of 3 independent lock-in amplifiers for external signal measuraments
with a sampling rate up to 50MHz (2 of the 3 channels) for high speed AC data
capture. It is capable of measuring areas up to 120 μm x 120 μm and can accept
samples of about 1 cm x 1 cm mounted on 10 mm or 12 mm magnetic steel disk
plates. The system resides on an optical table for vibration isolation. An additional
home made bungee-suspension system and acoustic isolator has been
implemented.
Equipment Specifications:
 TappingMode AFM, Phase contrast imaging, Torsional Resonance
Imaging Mode, Piezo-electric response measurements
 Lift Mode
 Tunneling AFM module for pA-nA current measurements
 Sampling rate up to 50MHz (2 channels) for high speed AC data capture
 High pixel density images up to 5k x 5k data points
 Allows for up to 8 simultaneous channels in real time scanning
 The standard sampling rate on the system is 500KHz
 The system includes digital active control of cantilever Q (Q control)
 The system supports NanoLithography and NanoManipulation software
Scientific Report 2005-2008
79
Characterization
Hhigh resolution three circles and low-angles X-Ray Diffractometer
SuperMat is equipped with an high resolution
x-ray diffractometer (Pananalytic X’Pert
MRD PRO, see Fig.1) which is an highly
advanced, versatile materials characterization
system. Interchangeable PreFIX incident and
diffracted beam optics can be configured for
optimal measurement of high resolution scans
and
reflectivity experiments.
By combining incident (with graded parabolic
x-ray mirror and four-bounce Ge(220)
monochromator) and diffracted (with triple
Fig.1. high resolution x-ray
axis setup using a three bounce (022) channel
diffractometer (Pananalytic X’Pert
cut Ge crystal) beam optics, high resolution
MRD PRO)
configuration can be applied to highly ordered
crystals and epitaxial thin films. It is useful to
examine lattice matched materials or the
structural perfection of materials. The system
can be used to accurately measure the width of
Bragg diffraction peaks from nearly perfect
single crystals over the range of a few seconds
of arc. In order to obtain the high resolution,
Fig.2. Pole figure of a
the angular divergence of the incident x-ray
GdRu2SrCu2O8 thin film.
beam has to be very small with little or no peak
broadening due to spectral dispersion and the goniometer has to be capable of very
accurate stepping. This system can also map regions in reciprocal space around the
Bragg reflections which can be useful to characterize relaxation of strained
epitaxial films and make pole figure maps (Fig. 2).
Reflectometry is an analytical technique for investigating thin layers. In
reflectivity experiments, the Xray reflection of a sample is
measured around the critical
angle (Fig.3). Below the critical
angle of total external reflection,
X-rays penetrate only a few
nanometers into the sample.
Above this angle the penetration
depth increases rapidly. At every
interface where the electron
density changes, part of the Xray beam is reflected. The
Fig.3. Reflectivity map of a Nb/PdNi multilayer.
80 Scientific Report 2005-2008
Characterization
interference of these partially reflected X-ray beams creates the oscillation pattern
observed in the reflectivity experiments. From these reflectivity curves, layer
parameters such as thickness and density, interface and surface roughness can be
determined through modeling.
Applications:
 High Resolution setup
o Rocking curves.
o Superlattice scans.
o Reciprocal space maps.
o Substrate offcut.
o Epitaxial layer tilt.
o Layer relaxation.
o Epitaxial layer mismatch.
o Pole figure maps.
 Reflectometry setup
o Identification of precipitates in materials.
o Analysis of nanoparticle sizes.
Scientific Report 2005-2008
81
Characterization
Scanning Electron Microscope equipped with EDS, WDS and EBSD analyses
The electron microscopy facility at SuperMat
is constituted by a tungsten/LaB6 scanning
electron microscope (SEM) (LEO EVO 50)
with a secondary electron detector for surface
imaging and a 4-quadrant back-scatter
electron detector for density imaging detector
(Fig.1). The analytical instrumentation is
comprised of an Oxford Instruments INCA
ENERGY (EDX) x-ray analysis system,
INCA WAVE (WDX) wavelength dispersive
x-ray spectrometer and INCA CRYSTAL
(EBSD) electron back-scatter diffraction.
Fig.1. Scanning electron microscope
equipped with EDX, WDX, EBSD.
In high resolution imaging under optimum
conditions for a suitable sample, a resolution
of the order of 5nm is achievable. This
allows images to be collected at a
magnification of X 100K or more, in
practice however magnifications up to X
20K are usually sufficient. Back
scattered electron-imaging produces a
density image particularly of polished
mineral surfaces and is used for
searching for small (< 1m) particles.
Fig.2. Wavelength dispersive spectroscopy of a
Other applications include elemental Sr2RuO4/Sr3Ru2O7 eutectic crystal.
zoning and multi-phase imaging. Energy
dispersive X-ray analysis of virtually all the chemical elements and alloys is
possible on a suitably surface polished. Materials routinely analysed include
superconducting and magnetic oxides like ruthenates,
manganites and cuprates. Detection limits for EDX analysis are
variable but typically around 1%. The software also allows for
multi-element x-ray mapping and line scanning. Wavelength
dispersive X-ray analysis using a five channel crystals
spectrometer allows analysis of elements from Boron up, again
with a variable detection limit but typically in the region of
Fig.3. EBSD pattern 0.01-0.05% in the element range calcium-gold. Single element
from a-b plane of
mapping and line scanning is possible. Electron backscatter
Sr3Ru2O7 single
diffraction (EBSD) is a microstructural technique used to
crystal. The pattern
examine the crystallographic orientation of many materials and
shows the Kikugi
to elucidate texture or preferred orientation of any crystalline
bands.
or polycrystalline materials. EBSD can be used to perform
crystal orientation mapping, defect studies, phase identification, grain boundary
82 Scientific Report 2005-2008
Characterization
and morphology studies, regional heterogeneity investigations, material
discrimination, microstrain mapping. EBSD is conducted using a SEM equipped
with a backscatter diffraction camera consisting of a phosphor screen and a CCD
camera. When the electrons impinge on the specimen they interact with the atomic
lattice planes of the crystalline structures, many of these interactions satisfy Bragg
conditions and undergo backscatter diffraction. Due to the angle of the specimen
these diffracted electrons can escape the material and are directed towards and
collide with the phosphor screen of the diffraction camera causing it to fluoresce,
this fluorescent light is then detected by a low light CCD. The diffracted electrons
produce a diffraction pattern, called Electron Backscatter Pattern (EBSP), which
shows Kikuchi bands, provided that the surface material (top ~20-100nm) is
suitably crystalline. EBSPs contain Kikuchi bands, which correspond to each of the
lattice diffracting planes and can be indexed individually by the Miller indices of
the diffracting plane which formed it (Fig.3). The bands formed can also be
analysed to show the deformation present within the material: pattern blurring
gives an indication of the plastic strain within the crystal and small rotations of the
pattern (compared to a perfect crystal at this orientation) indicate elastic strain.
Scientific Report 2005-2008
83
Characterization
PPMS 6000 with VSM and AC Susceptometer options
PPMS
Maximum field = ±9 T
Field Sweep rate = 11.2 Oe/s – 204 Oe/s
Temperature range = 1.9 K – 400 K
VSM option
Sensitivity =10-6 emu
Amplitude = 1- 3 mm
Frequency = 40 Hz
ACMS option
AC Field Amplitude = 1- 17 Oe
Frequency = 10 Hz – 10 kHz
Sensitivity = 10-8 emu
Maximum Sample dimension
= 3  3  3 mm3

Physical Property Measurements System (PPMS)
The Quantum Design PPMS is a system that can perform a variety of experiments,
i.e. magnetic and transport measurements, depending on the inserts used. The
PPMS of the “Laboratorio Regionale
SuperMat” can perform magnetic
measurements both by means of a Vibrating Sample Magnetometer (VSM) and by
means of an AC Susceptometer (ACMS).
The PPMS of our laboratory provides a magnetic field up to  9 T with a field
sweep rate of 11.2 Oe/s up to 204 Oe/s. The sample temperature can range from 1.9
K up to 400 K sweeping of 0.01 K/min up to 12 K/min. The PPMS is fully
automated by means of a software application.

Vibrating Sample Magnetometer (VSM) option
The VSM option for PPMS is a fast and sensitive DC magnetometer able to
resolve magnetization changes of less than 10-6 emu at a data rate of 1 Hz. In the
VSM, the samples vibrates with an amplitude of 1-3 mm at the frequency of 40 Hz
in the space that lies within the uniform magnetic field region of the PPMS
superconducting magnet. The change of the magnetic flux, due to the magnetic
moments of the vibrating sample, across a pick-up coil induces a synchronous
voltage that is proportional to the sample magnetic moment. Since the VSM is
previously calibrated by means of a Pd sample of known susceptibility, the
measurement of the induced voltage gives the magnetic moment of the sample.
Ranging the temperature and/or the magnetic field the VSM can measure, in
samples with dimensions 3  3  3 mm3, the magnetic moment as function of the
temperature (T) at fixed applied magnetic field (H), the magnetization loop at fixed
T and the magnetic relaxation.
84 Scientific Report 2005-2008
Characterization

AC Susceptometer (ACMS) option
The AC Measurements System (ACMS) is a PPMS option which allows to perform
the measurements of the AC susceptibility on samples with dimensions 3  3  3
mm3. In an AC magnetic measurements, an AC drive magnetic field is
superimposed on the DC field, causing a time-dependent moment in the sample.
The field of the time-dependent moment induces a voltage in the pickup coils
which is related to the AC magnetic response of the samples.
The ACMS insert contains an AC drive coil generating an AC magnetic field of
amplitude up to 17 Oe in a frequency range of 10 Hz to 10 kHz. The drive coil is
wound longitudinally around the detection coil set which are arranged in a first
gradiometer configuration in order to isolate the sample signal from the AC
excitation field. The insert fits directly in the PPMS sample chamber concentric
with the superconducting DC magnet of the PPMS. Moreover the ACMS is
connected to the automated temperature and field control system of the PPMS. The
sample is held within the pick-up coils on the end of a thin and rigid sample rod
and located in the space where the DC and AC magnetic field are homogenously
superimposed. During a measurement, the ACMS measures the in phase (dM’) and
the out of phase (dM’’) amplitude, with respect to the AC drive magnetic field, of
the change in the magnetic moment of the samples. The real (’) and imaginary
part (’’) of the AC susceptibility is then obtained by dividing dM’ and dM’’ for
the amplitude of the AC magnetic field. Moreover, the ACMS can detect in the
same measurement, the in phase and out of phase amplitude of the magnetic signal
referred to higher harmonics of the AC magnetic field. In this way the ACMS can
measure the first and the higher harmonics (up to the 10th harmonic) of the AC
susceptibility enabling to investigate the non linear magnetic response of the
sample.
In our laboratory, the PPMS is used for measuring the transport and magnetic
properties of superconductors, both conventional and unconventional like high-Tc
superconductors and oxy-picnitides superconductors. Moreover, the magnetic
properties of magnetic oxides like ruthenates and manganites, as well as
ferromagnet-superconductor hetero-structures, are also measured. These
measurements are typically performed on small sized single crystals, films and
powders as well as superconducting wires and tapes used in superconducting power
devices.
Scientific Report 2005-2008
85
Characterization
TG-DTA and DSC equipments
The thermal analysis of chemical-physical properties of the materials is performed
by using a SETARAM TG-DTA (Thermo-Gravimetric and Differential Thermal
Analyser) Setsys Evolution 1750 equipment (supplemented by a Pfeiffer Omnistar
Mass Spectrometry analyser), and by a Perkin-Elmer PYRIS DIAMOND DSC
(Differential Scanning Calorimeter). TG-DTA and DSC equipments at SuperMat
allow an accurate characterisation of the thermal properties of produced materials,
representing then a fundamental support to the laboratory activities in the synthesis
and growth processes of new superconducting and magnetic materials.
A TG analysis equipment consists in a precision balance and by a furnace. The
plate (or crucible) containing the material to be
analysed is placed in the centre of the furnace.
Each time the material absorbs or releases any gas
in
the
atmosphere
its
weight
varies
correspondingly. This variation, recorded by the
TGA, signals the occurrance of a reaction. The
SETARAM TGA equipment used at SuperMat has
a fixed zero balance. It has, indeed a feedback
system that restores the equilibrium between the
plates by the application of an electric field to the
reference plate. This mechanism allows to
maintain the sample constantly in the maximum
temperature point of the furnace. A DTA
equipment consists, instead, in two crucibles, one
containing the material and the other as a
reference (empty or filled with a reference material presenting linear properties in
the analysed temperature range), both placed in the centre of a furnace. DT signal,
that is the temperature difference between the two crucibles, is given by two
thermo-couples in contact with the crucibles. Each time the material experiments a
reaction or a phase transition, it absorbs or emits heath without varying its
temperature, this behaviour appears as a peak in the DT signal. Our TG-DTA
equipment has two crucibles, one for the sample and the other for reference, each
of them in contact with its thermocouple, the two are suspended to the precision
balance and placed in the centre of a furnace. This configuration allows
contemporaneous DT and TG measurements, from room temperature up to
1750°C, with the maximum sensibility and precision in its category. Our TG-DTA
equipment is also coupled, by a thermally stabilised channel, to a Mass
Spectrometry evolved gas analysing system.
A DSC analysis equipment consists in two sealed “plates”, one containing the
material to be analysed and the other empty (or filled with a reference material
presenting linear properties in the analysed temperature range), each in contact with
an heating element. DSC signal is the difference in the power applied to drive the
86 Scientific Report 2005-2008
Characterization
plates to the same temperature, monitored by means of two thermocouples. Each
time the material experiments a reaction or a phase transition, absorbs or emits
heath at constant temperature, causing a peak in the DSC signal. Perkin-Elmer
DSCs are the only equipment that performs real DSC measurements, the company
owning the patent, other equipments only perform simulated DSC measurements.
DSC equipment at SuperMat is ideal for materials having a low melting
temperature or with phase transitions occurring at temperatures within the range 180°C up to 700°C.
Scientific Report 2005-2008
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Characterization
88 Scientific Report 2005-2008
Publications
90
Scientific Report 2005-2008
Publications
2008 (with abstracts)
Record 1 of 39
Author(s): Salvato, M (Salvato, M.); Cirillo, M (Cirillo, M.); Lucci, M (Lucci, M.); Orlanducci,
S (Orlanducci, S.); Ottaviani, I (Ottaviani, I.); Terranova, ML (Terranova, M. L.); Toschi, F
(Toschi, F.)
Title: Charge Transport and Tunneling in Single-Walled Carbon Nanotube Bundles
Source: PHYSICAL REVIEW LETTERS, 101 (24): Art. No. 246804 DEC 12 2008
Abstract: We investigate experimentally the transport properties of single-walled carbon
nanotube bundles as a function of temperature and applied current over broad intervals of
these variables. The analysis is performed on arrays of nanotube bundles whose axes are
aligned along the direction of the externally supplied bias current. The data are found
consistent with a charge transport model governed by the tunneling between metallic
regions occurring through potential barriers generated by a nanotube's contact areas or
bundle surfaces. Based on this model and on experimental data, we describe quantitatively
the dependencies of the height of these barriers upon bias current and temperature.
DOI: 10.1103/PhysRevLett.101.246804
Record 2 of 39
Title: Strange attractors and synchronization dynamics of coupled Van der Pol-Duffing
oscillators
Author(s): Yamap, R; Filatrella, G
Source: COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL
SIMULATION 13 (6):1121-1130 2008
Abstract: We consider in this paper the synchronization dynamics of coupled chaotic Van
der Pol-Duffing systems. We first find that with the judicious choose of the set of initial
conditions, the model exhibits two strange chaotic attractors. The problem of synchronizing
chaos both on the same and different chaotic orbits of two coupled Van der Pol-Duffing
systems is investigated. The stability boundaries of the synchronization process between
two coupled driven Van der Pol model are derived and the effects of the amplitude of the
periodic perturbation of the coupling parameter on these boundaries are analyzed. The
results are provided on the stability map in the (q, K) plane. (C) 2006 Elsevier B.V. All
rights reserved.
DOI: 10.1016/j.cnsns.2006.09.014
Record 3 of 39
Title: Surface and structural disorder in MBE and sputtering deposited Cu thin films
revealed by X-ray measurements
Author(s): Salvato, M; Aurigemma, A; Tesauro, A; Attanasio, C
Source: VACUUM 82 (5):556-560 2008
Scientific Report 2005-2008
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Publications
Abstract: Copper thin films have been deposited on Si substrates by molecular beam
epitaxy (MBE) at different deposition rates varying from I up to 22 angstrom/s. X-ray
reflectivity and theta-2 theta measurements have shown that the surface roughness
correlation length, the structural disorder and the grain dimensions are strongly affected by
the deposition rate. Comparing these results with those obtained for sputtered deposited
thin films with a low deposition rate (2.5 angstrom/s), a clear similarity between the MBE
samples deposited with the highest deposition rate and the sputtering Cu films is observed.
This result has been interpreted considering the different energies of the particles that
approach the substrate in the two deposition techniques. (c) 2007 Elsevier Ltd. All rights
reserved.
DOI: 10.1016/j.vacuum.2007.07.058
Record 4 of 39
Title: Role of the external surfaces on the superconducting properties of
superconductor/normal metal trilayers
Author(s): Kushnir, VN; Ilyina, EA; Prischepa, SL; Cirillo, C; Attanasio, C
Source: SUPERLATTICES AND MICROSTRUCTURES 43 (2):86-92 2008
Abstract: Superconducting proximity effect is studied in superconductor/normal metal
trilayers. The dependences of the superconducting transition temperature T-c versus Nb
thickness in Cu/Nb/Cu systems and versus Cu thickness in Nb/Cu/Nb ones are described
by different values of the microscopical parameters. We attribute this difference to the
influence of the external surfaces of the Nb/Cu/Nb hybrids on the superconducting
properties of the system. (C) 2007 Elsevier Ltd. All rights reserved.
DOI: 10.1016/j.spmi.2007.06.004
Record 5 of 39
Title: Scanning tunneling microscope study of iron(II) phthalocyanine growth on metals
and insulating surfaces
Author(s): Scarfato, A; Chang, SH; Kuck, S; Brede, J; Hoffmann, G; Wiesendanger, R
Source: SURFACE SCIENCE 602 (3):677-683 2008
Abstract: The growth behavior of iron(II) phthalocyanine (FePc) molecules on Cu(111)
and on NaCl/Cu(111) surfaces has been studied by a variable-temperature scanning
tunneling microscope. Upon deposition at room temperature, FePc molecules with different
adsorption configurations form short-ranged ordered domains on Cu(111). In the second
FePc monolayer long-range ordering is observed. Molecule-molecule and moleculesubstrate interactions are discussed in comparison with previous findings for FePc on
Au(111). In order to reduce molecule-substrate interaction insulating NaCl layers are
introduced. FePc molecules adsorb on Cl- anion sites but show high mobility during
preparation. Our results provide detailed insight into the growth behavior of organic
molecules on metallic and insulating surfaces. (C) 2007 Elsevier B.V. All rights reserved.
DOI: 10.1016/j.susc.2007.11.011
Record 6 of 39
Title: Analysis of a power grid using a Kuramoto-like model
Author(s): Filatrella, G; Nielsen, AH; Pedersen, NF
92
Scientific Report 2005-2008
Publications
Source: EUROPEAN PHYSICAL JOURNAL B 61 (4):485-491 2008
Abstract: We show that there is a link between the Kuramoto paradigm and another
system of synchronized oscillators, namely an electrical power distribution grid of
generators and consumers. The purpose of this work is to show both the formal analogy
and some practical consequences. The mapping can be made quantitative, and under
some necessary approximations a class of Kuramoto-like models, those with bimodal
distribution of the frequencies, is most appropriate for the power-grid. In fact in the powergrid there are two kinds of oscillators: the "sources" delivering power to the "consumers".
DOI: 10.1140/epjb/e2008-00098-8
Record 7 of 39
Title: Subterahertz electrodynamics of the graphenelike superconductor CaAlSi
Author(s): Lupi, S; Baldassarre, L; Ortolani, M; Mirri, C; Schade, U; Sopracase, R;
Tamegai, T; Fittipaldi, R; Vecchione, A; Calvani, P
Source: PHYSICAL REVIEW B 77 (5): 2008
Abstract: We report an optical study of CaAlSi, a superconductor which displays both the
crystal structure of MgB2 and the electronic band structure of intercalated graphites. The
reflectivity of a CaAlSi single crystal was measured down to subterahertz frequencies and
to 3.3 K, with the use of coherent synchrotron radiation. A single superconducting gap in
the hexagonal planes and two gaps along the c axis were found and measured
consistently with the structure of the CaAlSi Fermi surface. The normal-state optical
conductivity is also anisotropic: in the ab plane, the plasma frequency is larger by more
than a factor of 2 than along the c axis. An analysis of the ab-plane spectral weight in
comparison with the corresponding quantity in a cuprate such as La2-xSrxCuO4 shows
that in CaAlSi the correlation effects are negligible.
DOI: 10.1103/PhysRevB.77.054510
Record 8 of 39
Title: Analysis of surface-bulk screening competition in the electron-doped Nd2-xCexCuO4
cuprate using x-ray photoemission spectroscopy
Author(s): Panaccione, G; Offi, F; Torelli, P; Vanko, G; Tjernberg, O; Lacovig, P; Guarino,
A; Fondacaro, A; Nigro, A; Sacchi, M; Brookes, NB; Monaco, G
Source: PHYSICAL REVIEW B 77 (12): 2008
Abstract: We report core level and valence band photoemission results obtained for Nd2xCexCuO4 (x = 0.15) single crystals and films by using both soft and hard x rays, hence,
with tunable depth sensitivity. When using hard x rays only, we observe distinct and energy
separated structures in the main 2p(5)3d(9)L peak of Cu 2p(3/2) and 2p(1/2) core levels,
including the well screened features located at the high kinetic energy side, which were
recently reported by Taguchi et al. [Phys. Rev. Lett. 95, 177002 (2005)]. By varying the
photoelectron takeoff angle, we analyze the difference in the screening properties between
surface and bulk, and we demonstrate the depth dependence of the electronic properties
by following the evolution of the bulk-related peak. The possible influence of the surface
conditions on the Cu 2p spectral features is also discussed.
DOI: 10.1103/PhysRevB.77.125133
Scientific Report 2005-2008
93
Publications
Record 9 of 39
Title: Resistive transitions in Nb/Cu0.41Ni0.59/Nb trilayers
Author(s): Prischepa, OO; Cirillo, C; Bell, C; Kushnir, VN; Aarts, J; Attanasio, C;
Kupryanov, MY
Source: JETP LETTERS 88:375 2008
Abstract: Nb/Cu0.41Ni0.59/Nb trilayers, with superconducting (S) Nb and ferromagnetic (F)
Nb/Cu0.41Ni0.59/Nb, has been experimentally studied as function of the F-layer thickness by
measuring the temperature dependence of the electrical resistance R(T). It is shown that
the shape and the width of the R(T) curves depends on the Cu 0.41Ni0.59 thickness, in
-coupling between the S-layers can be expected. To
explain the data we developed a qualitative model which makes the interconnection
uctures
more evident.
Record 10 of 39
Title: Superconducting properties of Nb thin films deposited on porous silicon templates
Author(s): Trezza, M; Prischepa, SL; Cirillo, C; Fittipaldi, R; Sarno, M; Sannino, D;
Ciambelli, P; Hesselberth, MBS; Lazarouk, SK; Dolbik, AV; Borisenko, EV; Attanasio, C
Source: JOURNAL OF APPLIED PHYSICS 104: 083917 - 2008
Abstract: Porous silicon, obtained by electrochemical etching, has been used as a
substrate for the growth of nanoperforated Nb thin films. The films, deposited by UHV
magnetron sputtering on the porous Si substrates, inherited their structure made of holes
of 5 or 10 nm diameter and of 10–40 nm spacing, which provide an artificial pinning
structure. The superconducting properties were investigated by transport measurements
performed in the presence of magnetic field for different film thickness and substrates with
different interpore spacing. Perpendicular upper critical fields measurements present
peculiar features such as a change in the Hc2 (T) curvature and oscillations in the field
dependence of the superconducting resistive transition width at H
1 T. This field value
is much higher than typical matching fields in perforated superconductors, as a
consequence of the small interpore distance.
DOI: 10.1063/1.2903522
Record 11 of 39
Title: Exact solution for a trapped fermi gas with population imbalance and BCS pairing
Author(s): Ying, ZJ; Cuoco, M; Noce, C; Zhou, HQ
Source: PHYSICAL REVIEW LETTERS 100 (14): 2008
Abstract: The problem of a two-component Fermi gas in a harmonic trap, with an
imbalanced population and a pairing interaction of zero total momentum, is mapped onto
the exactly solvable reduced BCS model. For a one-dimensional trap, the complete ground
state diagram is determined with various topological features in ground state energy
spectra. In addition to the conventional two-shell density profile of a paired core and
polarized outer wings, a three-shell structure as well as a double-peak superfluid
distribution are unveiled.
DOI: 10.1103/PhysRevLett.100.140406
94
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Publications
Record 12 of 39
Title: Comment on "Transverse rectification in superconducting thin films with arrays of
asymmetric defects" [Appl. Phys. Lett. 91, 062505 (2007)]
Author(s): Silhanek, AV; de Vondel, JV; Moshchalkov, VV; Leo, A; Metlushko, V; Ilic, B;
Misko, VR; Peeters, FM
Source: APPLIED PHYSICS LETTERS 92 (17): 2008
DOI: 10.1063/1.2920078
Record 13 of 39
Title: La0.7Ca0.3MnO3/YBa2Cu3O7-x/La0.7Ca0.3MnO3 heterostructures:
Superconducting and magnetic properties
Author(s): De Santis, A; Zola, D; Piano, S; Bobba, F; Giubileo, F; Longobardi, M;
Polichetti, M; Pace, S; Cucolo, AM
Editor(s): Ghoshray, A; Bandyopadhyay, B
Source: MAGNETIC MATERIALS 100313-15 2008
Conference Title: International Conference on Magnetic Materials (ICMM 2007)
Conference Date: DEC 11-16, 2007
Conference Location: Calcutta, INDIA
Abstract: We have realized highly epitaxial La0.7Ca0.3MnO3/YBa2CU3O7x/La0.7Ca0.3MnO3 (LCMO/YBCO/LCMO) trilayers grown on SrTiO3 (001) oriented single
crystal substrates by dc sputtering technique. Transport and magnetic measurements
indicate that the superconducting critical temperature is strongly suppressed while the
Curie temperature is higher than in a single LCMO film. These results are discussed in
terms of interaction between superconductivity and magnetism and strain relaxation of the
LCMO layer.
Record 14 of 39
Title: Magnetic excitations in La2CuO4 probed by indirect resonant inelastic x-ray
scattering
Author(s): Forte, F; Ament, LJP; van den Brink, J
Source: PHYSICAL REVIEW B 77 (13): 2008
Abstract: Recent experiments on La2CuO4 suggest that indirect resonant inelastic x-ray
scattering (RIXS) might provide a probe for transversal spin dynamics. We present in detail
a systematic expansion of the relevant magnetic RIXS cross section by using the ultrashort
core-hole lifetime (UCL) approximation. We compute the scattering intensity and its
momentum dependence in leading order of the UCL expansion. The scattering is due to
two-magnon processes and is calculated within a linear spin-wave expansion of the
Heisenberg spin model for this compound, including longer range and cyclic spin
interactions. We observe that the latter terms in the Hamiltonian enhance the first moment
of the spectrum if they strengthen the antiferromagnetic ordering. The theoretical spectra
agree very well with experimental data, including the observation that scattering intensity
vanishes for the transferred momenta q=(0,0) and q=(pi,pi). We show that at finite
temperature, there is an additional single-magnon contribution to the scattering with a
spectral weight proportional to T-3. We also compute the leading corrections to the UCL
approximation and find them to be small, setting the UCL results on a solid basis. All this
univocally points to the conclusion that the observed low temperature RIXS intensity in
Scientific Report 2005-2008
95
Publications
La2CuO4 is due to two-magnon scattering.
DOI: 10.1103/PhysRevB.78.134428
Record 15 of 39
Title: Anisotropic optical conductivity of Sr3Ru2O7
Author(s): Mirri, C; Baldassarre, L; Lupi, S; Ortolani, M;Fittipaldi, R;Vecchine, A; Calvani,P
Source: PHYSICAL REVIEW B 78: 2008 - 155132
Abstract: The optical conductivity
( ) of Sr3Ru2O7 has been studied both in the ab
planes, between 12 and 450 K, and along the c axis between 12 and 300 K. ab( ) is
Drude-type but, for increasing T, it shows a crossover around 300 K to a regime with
enhanced scattering rate, probably driven by a stronger coupling with the optical phonons.
The spectral weight shows the imprints of strong correlations, but less pronounced than in
a high-Tc material. Along the c axis, the Drude term has a much smaller plasma frequency,
and a strong absorption appears at 1 eV. These findings indicate an anisotropic metallic
state where electron-electron and electron-phonon interactions play a major role. This
picture may be reconciled with the local-density calculations reported in the literature,
which predict an insulating c axis, once those interactions are taken into account.
DOI: 10.1103/PhysRevB.77.155132
Record 16 of 39
Title: Exact solution for a trapped Fermi gas with population imbalance and BCS pairing.
Author(s): Ying, Zu-Jian; Cuoco, Mario; Noce, Canio; Zhou, Huan-Qiang
Source: Phys Rev Lett 100 (14):140406 2008
Abstract: The problem of a two-component Fermi gas in a harmonic trap, with an
imbalanced population and a pairing interaction of zero total momentum, is mapped onto
the exactly solvable reduced BCS model. For a one-dimensional trap, the complete ground
state diagram is determined with various topological features in ground state energy
spectra. In addition to the conventional two-shell density profile of a paired core and
polarized outer wings, a three-shell structure as well as a double-peak superfluid
distribution are unveiled.
Record 17 of 39
Title: Epitaxial growth of La0.7Ba0.3MnO3 thin films on MgO substrates: Structural,
magnetic, and transport properties
Author(s): Orgiani, P; Adamo, C; Barone, C; Galdi, A; Pagano, S; Petrov, AY; Quaranta,
O; Aruta, C; Ciancio, R; Polichetti, M; Zola, D; Maritato, L
Source: JOURNAL OF APPLIED PHYSICS 103 (9): 2008
Abstract: We report on structural, magnetic, and transport properties of La0.7Ba0.3MnO3
thin films, epitaxially grown on MgO substrates. Despite the quite similar structural features
if compared to crystalline manganite films, our samples show a metal-insulator transition
temperature of about 200 K, sizeably lower than the bulk-value (T-MI similar or equal to
345 K). Moreover, the magnetotransport properties show the absence of saturation in the
magnetoresistance and localization phenomena at low temperatures (T < 30 K). The
temperature behavior of the magnetization shows a Curie temperature T-c value above
room temperature, ruling out effects due to oxygen deficiency. All these findings are
analyzed in terms of possible physical mechanisms related to the growth in the presence
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of large mismatch between film and substrate lattice parameters. (c) 2008 American
Institute of Physics.
DOI: 10.1063/1.2903522
Record 18 of 39
Title: The decomposition reaction of lithium amide studied by anelastic spectroscopy and
thermogravimetry
Author(s): Palumbo, O; Paolone, A; Rispoli, P; D'Orazio, A; Cantelli, R; Chandra, D
Source: INTERNATIONAL JOURNAL OF MATERIALS RESEARCH 99 (5):487-490 2008
Abstract: The high temperature decomposition transformation of lithium amide into imide
has been studied by anelastic spectroscopy and thermogravimetry. At the amide-to-imide
phase transformation a huge elastic modulus increase takes place, whose change
increases with the evolution of the decomposition. The modulus variation has been used to
monitor the time and temperature progression of the reaction, and indications have been
obtained that the reaction rates are faster than those usually reported. Moreover, formation
of different phases is also detected at extremely low concentrations.
DOI: 10.3139/146.101665
Record 19 of 39
Title: Integrating superconductive and optical circuits
Author(s): Stella, F; Casalboni, M; Cirillo, M; Merlo, V; Palazzesi, C; Pepe, GP;
Prosposito, P; Salvato, M
Source: APPLIED PHYSICS LETTERS 92 (20): 2008
Abstract: We have integrated on oxidized silicon wafers superconductive films and
Josephson junctions along with sol-gel optical channel waveguides. The fabrication
process is carried out in two steps that result to be solid and noninvasive. It is
demonstrated that 660 nm light, coupled from an optical fiber into the channel sol-gel
waveguide, can be directed toward superconducting tunnel junctions whose currentvoltage characteristics are affected by the presence of the radiation. The response of the
junction biased at various currents as a function of the optical pumping is presented and
discussed according to a nonequilibrium superconductivity model. (C) 2008 American
Institute of Physics.
DOI: 10.1063/1.2931700
Record 20 of 39
Title: Normal zone propagation in a MgB2 conduction cooled test magnet
Author(s): Cavaliere, V; Matrone, A; Masullo, G; Quarantiello, R; Saggese, A; Pace, S;
Gambardella, U
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 18 (2):924-927
2008
Conference Title: 20th International Conference on Magnet Technology
Conference Date: AUG 27-31, 2007
Conference Location: Philadelphia, PA
Abstract: In order to investigate the quench behavior of conduction cooled MgB2
magnets, a 100 mm inner bore diameter, 0.84 T at 20 K magnet has been built and tested.
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The test magnet consists of 4 double pancakes wound with the MgB2/Ni-Cu-Fe tape
produced by Columbus. Each coil is cooled by means of a 2 mm thick copper disk placed
during winding at the middle of the double pancake; after winding the double pancakes
have been separately epoxy impregnated. Several experiments have been performed
inducing a local transition in the coil by means of a controlled heater placed on the double
pancake surface. The propagation of the normal zone has been monitored by means of 8
voltage probes positioned along the tape during coil manufacturing. Each voltage probe
detects the voltage drop across a tape length of 30 mm. The experiments have been
performed at different temperatures while keeping the magnet current constant during
quench. In the paper we report an analysis of the quench propagation velocity
measurements and a numerical investigation of the thermal and electrical behavior of the
magnet.
DOI: 10.1109/TASC.2008.922527
Record 21 of 39
Title: Thermomagnetic instability and critical current density in MgB2 monofilamentary
tapes
Author(s): Zola, D; Polichetti, M; Adesso, MG; Kovac, P; Martini, L; Pace, S
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 468 (7-10):761764 2008
Conference Title: Vortex V Conference on Nanoscience and Engineering in
Superconductivity
Conference Date: SEP 08-14, 2007
Conference Location: Rhodes, GREECE
Abstract: Thermomagnetic instability in MgB2 monofilamentary tapes with paramagnetic
nickel alloy and superconducting niobium matrix, has been investigated by measuring
hysteresis loops and magnetic relaxations. The analysis has been performed on
monofilamentary tapes where titanium, tungsten and silicon carbide impurities have been
added to the superconducting phase. We show that the addition of impurities results in an
increase of the thermomagnetic instability at low field without considerably increasing the
critical current density. The analysis of the magnetic relaxation measurements shows a
very strong pinning in MgB2, corresponding to an intrinsic critical current density larger
than the experimental measured value. The interplay between thermal and magnetic
diffusion limits the critical current density in MgB2 in spite of impurities addition. (C) 2008
Elsevier B.V. All rights reserved.
DOI: 10.1016/j.physc.2007.11.042
Record 22 of 39
Title: Thickness dependence of vortex critical velocity in wide Nb films
Author(s): Grimaldi, G; Leo, A; Nigro, A; Pace, S; Cirillo, C; Attanasio, C
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 468 (7-10):765768 2008
Conference Title: Vortex V Conference on Nanoscience and Engineering in
Superconductivity
Conference Date: SEP 08-14, 2007
Conference Location: Rhodes, GREECE
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Abstract: Pulsed I-V measurements performed on wide Nb films of different thickness
show the electronic instability, at high driving currents, predicted by Larkin and
Ovchinnikov (LO). We find that the associated vortex critical velocity nu* decreases with
the film thickness, and its temperature and magnetic field dependences exhibit some
discrepancies with respect to the LO theoretical results. (C) 2008 Elsevier B.V. All rights
reserved.
DOI: 10.1016/j.physc.2007.11.043
Record 23 of 39
Title: Local study of the Mg1-xAlxB2 single crystals by scanning tunneling spectroscopy in
magnetic field up to 3 Tesla
Author(s): Giubileo, F; Bobba, F; Scarfato, A; Cucolo, AM; Kohen, A; Roditchev, D;
Zhigadlo, ND; Karpinski, J
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 468 (7-10):828831 2008
Conference Title: Vortex V Conference on Nanoscience and Engineering in
Superconductivity
Conference Date: SEP 08-14, 2007
Conference Location: Rhodes, GREECE
Abstract: We have performed local tunneling spectroscopy on high quality Mg 1-xAlxB2
single crystals by means of variable temperature scanning tunneling spectroscopy in
magnetic field up to 3 Tesla. Single gap conductance spectra due to c-axis tunneling were
extensively measured, probing different amplitudes of the three-dimensional Delta(pi) as a
function of Al content (i.e. as a function of the critical temperature T C). Temperature and
magnetic field dependences of the conductance spectra were studied in S-I-N
configuration: the effect of the doping resulted in a monotonous reduction of the locally
measured TC down to 24 K for x = 0.2. The magnetic field dependence was studied in a
local way: An estimation for upper critical field H -c2 was inferred from the evolution of the
tunneling spectra with the field perpendicular to the sample surface, for different doping
levels. The high spatial resolution of the STS technique allowed us to evidence possible
non-homogeneities of the superconducting properties on the sample surface with variation
of in the same sample depending on different local levels of doping. The locally measured
upper critical field resulted to vary for different dopings, and the maximum value H -c2 similar
or equal to 3 T was found for samples with T C = 33 K. The evolution of the density of states
(DOS) was found to be characterized by two distinct regimes separated by a crossover
region. Our results indicate a rapid suppression of the intrinsic term in pi-band
superconductivity for 0 T < B < 0.5 T. At high fields (0.8 T < B < 3 T) the superconductivity
in the pi-band survives uniquely due to the coupling to the (sigma-band. The shape of
tunneling spectra suggests an important role played by the quasiparticle inter-band
scattering.
DOI: 10.1016/j.physc.2007.11.079
Record 24 of 39
Title: Thermal treatments and evolution of bulk Nd1.85Ce0.15CuO4 morphology
Author(s): Uthayakumar, S; Fittipaldi, R; Guarino, A; Vecchione, A; Romano, A; Nigro,
A; Habermeier, H U; Pace, S
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 468: 2271 2008
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Abstract: The present work focuses on the sintering of the Nd1.85Ce0.15CuO4 phase in the
form of sputtering targets. The method of manufacture, based on a careful control of the
microstructure, is of fundamental importance in ensuring the reliability of Nd1.85Ce0.15CuO4
targets and the subsequent realization of high-quality sputter-deposited thin films. In this
study the Nd1.85Ce0.15CuO4 targets were prepared by a standard solid state reaction
technique. We investigated the influence of the thermal treatment on the phase formation
by employing X-ray diffraction (XRD) technique, scanning electron microscopy (SEM) and
energy dispersion spectrometry (EDS) analyses. As the growth temperature increases
beyond the eutectic point, the achievement of a liquid phase yields a homogeneous grain
growth. The results presented here are expected to be of particular usefulness in tailoring
the growth of high quality thin films.
DOI: 10.1016/j.physc.2007.11.079
Record 25 of 39
Title: Coexistence of itinerant ferromagnetism and a nonunitary superconducting state with
line nodes: Possible application to UGe2
Author(s): Linder, J; Sperstad, IB; Nevidomskyy, AH; Cuoco, M; Sudbo, A
Source: PHYSICAL REVIEW B 77 (18): 2008
Abstract: We construct a mean-field theory for itinerant ferromagnetism coexisting with a
norrunitary superconducting state, where only the majority-spin band is gapped and
contains line nodes, while the minority-spin band is gapless at the Fermi level. Our study is
motivated by recent experimental results, which indicate that this may be the physical
situation realized in the heavy-fermion compound UGe2. We investigate the stability of the
mean-field solution of the magnetic and superconducting order parameters. Also, we
provide theoretical predictions for experimentally measurable properties of such a
nonunitary superconductor: the specific heat capacity, the Knight shift, and the tunneling
conductance spectra. Our study should be useful for direct comparison with experimental
results and also for further predictions of the physics that may be expected in
ferromagnetic superconductors.
DOI: 10.1103/PhysRevB.77.184511
Record 26 of 39
Title: A simple statistical phenomenological model for cation substitutions in Nd1+xBa2xCu3O7-(delta+x/2)
Author(s): Gombos, M; Varesi, E; Tedesco, P; Vecchione, A; Pace, S
Source: PHILOSOPHICAL MAGAZINE 88 (9):1389-1399 2008
Abstract: The first results are presented of calculations using a quite simple
phenomenological model developed to simulate the cationic substitutions in Nd 1+xBa2xCu3O7+x/2-delta (Nd123). Although elementary concepts from statistical mechanics are used
in the model, significant results have been obtained, such as the reconstruction of the
substitution region limits and their dependence on temperature. Particularly interesting is
the prediction of strong temperature dependence for the minimum substitution parameter,
x(min).
DOI: 10.1080/14786430802178079
Record 27 of 39
Title: Multiple superconducting transitions in the Sr3Ru2O7 region of Sr3Ru2O7-Sr2RuO4
100 Scientific Report 2005-2008
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eutectic crystals
Author(s): Kittaka, S; Fusanobori, S; Yonezawa, S; Yaguchi, H; Maeno, Y; Fittipaldi, R;
Vecchione, A
Source: PHYSICAL REVIEW B 77 (21): 2008
Abstract: We report the superconducting properties of Sr 3Ru2O7-Sr2RuO4 eutectic
crystals, which consist of the spin-triplet superconductor Sr2RuO4 with a monolayer
stacking of RuO2 planes and the metamagnetic normal metal Sr3Ru2O7 with a bilayer
stacking. Although Sr3Ru2O7 so far has not been reported to exhibit superconductivity, our
ac susceptibility measurements revealed multiple superconducting transitions that occur in
the Sr3Ru2O7 region of the eutectic crystals. The diamagnetic shielding essentially reached
the full fraction at low ac fields parallel to the c axis. However, both the shielding fraction
and the onset temperature are easily suppressed by ac fields larger than 0.1 mT rms and
no anomaly was observed in the specific heat. Moreover, the critical field curves of these
transitions have a positive curvature near zero fields, which is different from the upper
critical field curve of the bulk Sr2RuO4. These facts suggest that the superconductivity
observed in the Sr3Ru2O7 region is not a bulk property. To explain these experimental
results, we propose the scenario that stacking RuO2 planes, which are the building blocks
of superconducting Sr2RuO4, are contained in the Sr3Ru2O7 region as stacking faults.
DOI: 10.1103/PhysRevB.77.214511
Record 28 of 39
Title: Lithium nitride as hydrogen storage material
Author(s): Palumbo, O; Paolone, A; Cantelli, R; Chandra, D
Source: INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 33 (12):3107-3110 2008
Conference Title: 2nd World Congress of Young Scientists on Hydrogen Energy
Conference Date: JUN 06-08, 2007
Conference Location: Turin, ITALY
Abstract: In this paper we report studies of the elastic modulus and energy dissipation in
lithium amide (LiNH2) during its high temperature decomposition into imide (Li2NH),
according to the reaction: 2LiNH(2) -> Li2NH + NH3. The dynamic modulus variations
allow the time and temperature evolution of decomposition to be monitored. It is shown
that the formation of different phases are detected also at extremely low concentrations.
During the amide to imide transformation a considerable increase of the modulus is
detected. We found that the reaction rates are remarkably faster than those usually
reported. The anelastic spectrum of Li3N presents a strong variation in the elastic
modulus, corresponding to the conversion from the beta to the alpha phase. (c) 2008
International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights
reserved.
DOI: 10.1016/j.ijhydene.2008.02.053
Record 29 of 39
Title: Flux flow velocity instability in wide superconducting films
Author(s): Grimald, G.; Leo, A.; Nigro, A.; Pace, S.; Angrisani, A.A.; Attanasio, C.
Source: Journal of Physics: Conference Series012111 (6 pp.) 2008
Conference Title: 8th European Conference On Applied Superconductivity
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Conference Date: Brussels
Conference Location: Belgium
Abstract: To understand energy losses related to vortex high velocity we study the critical
voltage in the current-voltage (I-V) characteristics above which in the flux flow regime a
sudden voltage jump appears. Different mechanisms have been proposed to account for
the existence of a critical vortex velocity corresponding to the observed instability, such as
heating effects or intrinsic non equilibrium phenomena. Nevertheless experimental studies
of flux flow instabilities in wide superconducting films have been less investigated. We
report on critical voltage measurements in Nb wide superconducting strips. We perform I-V
measurements as function of magnetic field by using different bias modes (sweeping,
compensated long and short pulsing). The magnetic field dependence of the critical
voltage shows different features in the three operation modes. We quantitatively estimate
self-heating effects taking into account cryogenic stabilization criteria and thermal diffusion
calculations, and we demonstrate that the observed dynamics instabilities are not triggered
by Joule self-heating. The Larkin-Ovchinnikov (LO) theory of non linear effects in the
vortex motion has been then applied to interpret the critical velocity results. The magnetic
field dependence of the vortex critical velocity shows some discrepancies with the LO
predicted behaviour.
DOI: 10.1088/1742-6596/97/1/012111
Record 30 of 39
Title: Spin-orbital-lattice physics in Ca-based ruthenates
Author(s): Cuoco, M; Forte, F; Noce, C
Editor(s): Barbara, B; Imry, Y; Sawatzky, G; Stamp, PCE
Source: QUANTUM MAGNETISM67-84 2008
Conference Title: Pacific-Institute-of-Theoretical-Physics Summer School on Quantum
Magnetism
Conference Date: JUN, 2006
Conference Location: Les Houches, FRANCE
Abstract: In this paper, we review some recent results, obtained by means of exact
diagonalization technique, about the competition between the octahedral distortions and
the Coulomb interactions for the t(2g) electrons in layered Ca-based ruthenates. We
provide a scenario where the flattening of the octahedra is the driving mechanism for
yielding an antiferromagnetic state with C- or G-type structure and different orbital
configurations. On the other hand, we show that the elongation of the octahedra gives rise
to a ground state with incomplete ferromagnetism. To further account for unconventional
spin-orbital configurations in the Ca2RuO4 system, where all the t(2g) degrees of freedom
contribute, the role of the spin-orbit coupling and its competition with compressed
octahedral deformations are investigated. One of the main findings is the occurrence of
anisotropic spin patterns with partially filled orbital occupation and coexisting ferro- and
antiferro-type correlations in the spin/orbital channel.
Record 31 of 39
Title: An anelastic spectroscopy, differential scanning calorimetry and X-ray diffraction
study of the crystallization process of Mg-Ni-Fe alloys
Author(s): Palumbo, O; Paolone, A; Cantelli, R; Giannini, C; Gagliardi, A; Reale, P;
Scrosati, B; Lo Russo, S; Maddalena, A; Palade, P; Principi, G; Schinteie, G
102 Scientific Report 2005-2008
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Source: JOURNAL OF ALLOYS AND COMPOUNDS 463 (1-2):148-152 2008
Abstract: The effects of heating-induced crystallization on the structural and mechanical
properties of Mg-Ni-Fe amorphous ribbons were studied by anelastic spectroscopy,
differential scanning calorimetry (DSC) and X-ray diffraction. DSC results show that the
crystallization occurs through several non-reversible steps, which correspond to significant
changes in the Young's modulus and concomitant irreversible elastic energy loss peaks.
Moreover, an anelastic peak is found at 215 K, which for the first time indicates the
presence of some dynamical process related to the simultaneous presence of different
phases. The formation of a metastable Mg6Ni phase is detected, which transforms into Mg
and Mg2Ni stable phases. A quantitative analysis of the different phases present at the
different steps was also carried out. (C) 2007 Elsevier B.V. All rights reserved.
DOI: 10.1016/j.jallcom.2007.08.081
Record 32 of 39
Title: Superconductivity in Sr/sub 2/RuO/sub 4/-Sr/sub 3/Ru/sub 2/O/sub 7/ eutectic
crystals
Author(s): Fittipaldi, R.; Vecchione, A.; Ciancio, R.; Pace, S.; Cuoco, M.; Stornaiuolo, D.;
Born, D.; Tafuri, F.; Olsson, E.; Kittaka, S.; Yaguchi, H.; Maeno, Y.
Source: Europhysics Letters27007 (5 pp.) 2008
Abstract: Superconducting behavior has been observed in the Sr/sub 2/RuO/sub 4/Sr/sub 3/Ru/sub 2/O/sub 7/ eutectic system as grown by the flux-feeding floating-zone
technique. A supercurrent flows across a single interface between Sr/sub 2/RuO/sub 4/Sr/sub 3/Ru/sub 2/O/sub 7/ areas at distances that are far beyond those expected in a
conventional proximity effect. The current-voltage characteristics within the Sr/sub
3/Ru/sub 2/O/sub 7/ macrodomain, as extracted from the eutectic, exhibit signatures of
superconductivity in the bilayered Sr/sub 3/Ru/sub 2/O/sub 7/ region. Detailed
microstructural, morphological and compositional analyses address issues on the
concentration and the size of Sr/sub 2/RuO/sub 4/ inclusions within the Sr/sub 3/Ru/sub
2/O/sub 7/ matrix. We speculate on the possibility of inhomogeneous superconductivity in
the eutectic Sr/sub 3/Ru/sub 2/O/sub 7/ and exotic pairing induced by the Sr/sub
2/RuO/sub 4/ inclusions.
DOI: 10.1209/0295-5075/83/27007
Record 33 of 39
Title: Proximity effect between an unconventional superconductor and a ferromagnet with
spin bandwidth asymmetry
Author(s): Cuoco, M.; Romano, A.; Noce, C.; Gentile, P.
Source: Physical Review B (Condensed Matter and Materials Physics)054503-1-13 2008
Abstract: We study the proximity effect within a junction made of an unconventional
superconductor (US) and a ferromagnet (F) in the clean limit with high barrier
transparency. Superconductivity in the US side is described by an extended Hubbard
model with intersite attractive interaction, while metallic ferromagnetism in the F side is
assumed to be originated by a relative change in the bandwidths of electrons with opposite
spin. The effect of this mass-split mechanism is analyzed in conjunction with the usual
Stoner-like one, where one band is rigidly shifted with respect to the other, due to the
presence of a constant exchange field. Starting from the numerical solution of the
Bogoliubov-de Gennes equations, we show that the two above mentioned mechanisms for
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ferromagnetism lead to different features as concerns the formation at the interface of
dominant and subdominant superconducting components, as well as their propagation in
the ferromagnetic side. This considerably affects the opening of gaplike structures in the
local density of states for majority and minority spin electrons, leading to distinct effects as
one moves toward the half-metallic regime, where the density of the minority carriers
becomes vanishing.
DOI: 10.1103/PhysRevB.78.054503
Record 34 of 39
Title: Proximity effect between an unconventional superconductor and a ferromagnet with
spin bandwidth asymmetry
Author(s): Cuoco, M; Romano, A; Noce, C; Gentile, P
Source: PHYSICAL REVIEW B 78 (5): 2008
Abstract: We study the proximity effect within a junction made of an unconventional
superconductor (US) and a ferromagnet (F) in the clean limit with high barrier
transparency. Superconductivity in the US side is described by an extended Hubbard
model with intersite attractive interaction, while metallic ferromagnetism in the F side is
assumed to be originated by a relative change in the bandwidths of electrons with opposite
spin. The effect of this mass-split mechanism is analyzed in conjunction with the usual
Stoner-like one, where one band is rigidly shifted with respect to the other, due to the
presence of a constant exchange field. Starting from the numerical solution of the
Bogoliubov-de Gennes equations, we show that the two above mentioned mechanisms for
ferromagnetism lead to different features as concerns the formation at the interface of
dominant and subdominant superconducting components, as well as their propagation in
the ferromagnetic side. This considerably affects the opening of gaplike structures in the
local density of states for majority and minority spin electrons, leading to distinct effects as
one moves toward the half-metallic regime, where the density of the minority carriers
becomes vanishing.
DOI: 10.1103/PhysRevB.78.054503
Record 35 of 39
Title: Local dynamical lattice instabilities: Prerequisites for resonant pairing
superconductivity
Author(s): Ranninger, J; Romano, A
Source: PHYSICAL REVIEW B 78 (5): 2008
Abstract: Fluctuating local diamagnetic pairs of electrons, embedded in a Fermi sea, are
candidates for non-phonon-mediated superconductors without the stringent conditions on
T-c which arise in phonon-mediated BCS classical low-T-c superconductors. The local
accumulations of charge, from which such diamagnetic fluctuations originate, are
irrevocably coupled to local dynamical lattice instabilities and form composite charge-lattice
excitations of the system. For a superconducting phase to be realized, such excitations
must be itinerant spatially phase-coherent modes. This can be achieved by resonant pair
tunneling in and out of polaronic cation-ligand sites. Materials in which superconductivity
driven by such local lattice instability can be expected have a T-c which is controlled by the
phase stiffness rather than the amplitude of the diamagnetic pair fluctuations. Above T-c a
pseudogap phase will be maintained up to T*, at which this pairing amplitude disappears.
We discuss the characteristic local charge and lattice properties which characterize this
pseudogap phase and which form the prerequisites for establishing a phase-coherent
104 Scientific Report 2005-2008
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macroscopic superconducting state.
DOI: 10.1103/PhysRevB.78.054527
Record 36 of 39
Title: A new method to detect the vortex glass phase and its evidence in YBCO
Author(s): Adesso, MG; Polichetti, M; Pace, S
Source: JOURNAL OF PHYSICS-CONDENSED MATTER 20 (38): 2008
Abstract: The evidence of the vortex glass phase has been obtained by analysing the
nonlinear magnetic response of type-II superconductors. The method introduced here is
based on a combined frequency dependence analysis of the real and imaginary part of the
1st and 3rd harmonics of the AC magnetic susceptibility. The analysis has been performed
by taking into account both the components and the Cole-Cole plots (i.e. the imaginary part
as a function of the real part). Numerical simulations have been used to identify the
fingerprints of the magnetic behaviour in the vortex glass phase. These characteristics
allowed the vortex glass phase to be distinguished from the other disordered phases, even
those showing similar electrical properties. Finally, this method has been successfully
applied to detecting the vortex glass phase in an YBCO bulk melt-textured sample.
DOI: 10.1088/0953-8984/20/38/385211
Record 37 of 39
Title: Field emission from a selected multiwall carbon nanotube
Author(s): Passacantando, M; Bussolotti, F; Santucci, S; Di Bartolomeo, A; Giubileo, F;
Iemmo, L; Cucolo, AM
Source: NANOTECHNOLOGY 19 (39): 2008
Abstract: The electron field emission characteristics of individual multiwalled carbon
nanotubes were investigated by a piezoelectric nanomanipulation system operating inside
a scanning electron microscopy chamber. The experimental set-up ensures a precise
evaluation of the geometric parameters (multiwalled carbon nanotube length and diameter
and anode-cathode separation) of the field emission system. For several multiwalled
carbon nanotubes, reproducible and quite stable emission current behaviour was obtained,
with a dependence on the applied voltage well described by a series resistance modified
Fowler-Nordheim model. A turn-on field of similar to 30 V mu m(-1) and a field
enhancement factor of around 100 at a cathode-anode distance of the order of 1 mu m
were evaluated. Finally, the effect of selective electron beam irradiation on the nanotube
field emission capabilities was extensively investigated.
DOI: 10.1088/0957-4484/19/39/395701
Record 38 of 39
Title: Coexistence of strong pairing correlations and itinerant ferromagnetism arising from
spin asymmetric bandwidths: A reduced BCS model study
Author(s): Ying, ZJ; Cuoco, M; Noce, C; Zhou, HQ
Source: PHYSICAL REVIEW B 78 (10): 2008
Abstract: We investigate the conditions for the occurrence of the coexisting phases that
exhibit singlet superconductivity and itinerant ferromagnetism arising from spin asymmetric
bandwidths. The exact solution for a reduced BCS pairing model with spin dependent
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bandwidths is used to determine the ground-state diagram as a function of the coupling
parameter, the total density, and the topology of the single-particle spectrum. A spinpolarized superconducting state is obtained in the regime of large pair couplings with a
strong bandwidth asymmetry. The analysis reveals that, for such a type of ferromagnetism,
small (large) values of the density of states at energies close to the edges of the band
enhance (hinder) the tendency toward a coexistence of strong pairing correlations and
finite spin polarizations.
DOI: 10.1103/PhysRevB.78.104523
Record 39 of 39
Title: Low-field transport measurements in superconducting Co/Nb/Co trilayers
Author(s): Carapella, G; Russo, F; Costabile, G
Source: PHYSICAL REVIEW B 78 (10): 2008
Abstract: We report transport measurements in a superconducting Co/Nb/Co trilayer
based on elemental ferromagnetic Co and elemental superconducting Nb. The trilayer
behaves as a superconducting valve, can be operated at liquid-helium temperature, and
can switch from superconductive to normal state in weak applied in-plane magnetic fields.
Current-voltage curves, critical currents as a function of temperature and magnetic field, as
well as preparation of superconductive or resistive state are addressed here. Data analysis
suggests that the superconducting valve behavior can be accounted for by a glassy vortex
phase induced in the superconductor by the stray fields from domain walls proliferating
around the coercive fields of the ferromagnetic electrodes.
DOI: 10.1103/PhysRevB.78.104529
2007
Record 1 of 52
Title: Generalized coupling in the Kuramoto model
Author(s): Filatrella, G; Pedersen, NF; Wiesenfeld, K
Source: PHYSICAL REVIEW E 75 (1): Part 2 2007
DOI: 10.1103/PhysRevE.75.017201
Record 2 of 52
Title: Influence of grain boundaries and Sn distribution on the H-T phase diagram of
Nb3Sn
Author(s): Adesso, MG; Flukiger, R; Uglietti, D; Polichetti, M; Pace, S
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 (2):2619-2622
2007
Conference Title: Applied Superconductivity Conference 2006
Conference Date: AUG 27-SEP 01, 2006
Conference Location: Seattle, WA
106 Scientific Report 2005-2008
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DOI: 10.1109/TASC.2007.898248
Record 3 of 52
Title: Superparamagnetic behavior of ferromagnetic nanoclusters in RuSr2GdCu2O8 and
RuSr2Gd1.6Ce0.4Cu2O10 samples observed by AC and DC magnetic measurements
Author(s): Cimberle, MR; Masini, R; Canepa, F; Costa, G; Artini, C; Vecchione, A;
Polichetti, M; Gombos, M; Adesso, MG
Source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 316 (2):E529-E531
2007
Conference Title: Joint European Magnetic Symposia (JEMS 06)
Conference Date: JUN 26-29, 2006
Conference Location: San Sebastian, SPAIN
DOI: 10.1016/j.jmmm.2007.03.039
Record 4 of 52
Title: Jahn-Teller coupling in Ca-based layered ruthenates
Author(s): Cuoco, M; Forte, F; Noce, C
Editor(s): Avella, A; Mancini, A
Source: Lectures on the Physics of Strongly Correlated Systems XI 918289-296 2007
Conference Title: 11th Training Course in the Physics of Strongly Correlated Systems
Conference Date: OCT 02-13, 2006
Conference Location: Salerno, ITALY
Record 5 of 52
Title: Field tunable spin/orbital correlations in Ca-based ruthenates
Author(s): Cuoco, M; Forte, F; Noce, C
Source: PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 244 (7):23222326 2007
Conference Title: 30th International Conference of Theoretical Physics
Conference Date: SEP 09-14, 2006
Conference Location: Ustron, POLAND
DOI: 10.1002/pssb.200674606
Record 6 of 52
Title: Electronic and magnetic order in La0.7Ca0.3MnO3/YBa2Cu3O7-delta superlattices
Author(s): Deen, PP; Yokaichiya, F; Paolasini, L; Lee, S; de Santis, A; Bobba, F; Cucolo,
AM
Source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2):2286-2288
Part 3 2007
DOI: 10.1016/j.jmmm.2006.10.750
Record 7 of 52
Scientific Report 2005-2008
107
Publications
Title: Thermal expansion of Josephson junctions as an elastic response to an effective
stress field
Author(s): Sergeenkov, S; Rotoli, G; Filatrella, G; Araujo-Moreira, FM
Source: PHYSICAL REVIEW B 75 (1): 2007
DOI: 10.1103/PhysRevB.75.014506
Record 8 of 52
Title: Systematic study of disorder induced by neutron irradiation in MgB2 thin films
Author(s): Ferrando, V; Pallecchi, I; Tarantini, C; Marre, D; Putti, M; Ferdeghini, C; Gatti,
F; Aebersold, HU; Lehmann, E; Haanappel, E; Sheikin, I; Orgiani, P; Xi, XX
Source: JOURNAL OF APPLIED PHYSICS 101 (4): 2007
DOI: 10.1063/1.2405121
Record 9 of 52
Title: Effects of neutron irradiation on magnesium diboride thin films
Author(s): Ferrando, V; Pallecchi, I; Tarantini, C; Putti, M; Aebersold, HU; Lehmann, E;
Orgiani, P; Tumino, A; Xi, XX; Ferdeghini, C
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 (2):2858-2861
2007
Conference Title: Applied Superconductivity Conference 2006
Conference Date: AUG 27-SEP 01, 2006
Conference Location: Seattle, WA
DOI: 10.1109/TASC.2007.899998
Record 10 of 52
Title: Thermal propagation of fluxons in two-dimensional Josephson junction arrays
Author(s): Filatrella, G.; Girotti, S.; Rotoli, G.
Source: Physical Review B (Condensed Matter and Materials Physics)|Physical Review B
(Condensed Matter and Materials Physics) vol.75, no.554510-1-9 2007
Record 11 of 52
Title: Generalized coupling in the Kuramoto model.
Author(s): Filatrella, G; Pedersen, N F; Wiesenfeld, K
Source: Phys Rev E Stat Nonlin Soft Matter Phys 75 (1 Pt 2):017201 2007
Record 12 of 52
Title: Stability measurements in multifilamentary MgB2 tapes
Author(s): Gambardella, U; Saggese, A; Sessa, P; Guarino, A; Pace, S; Masullo, G;
Matrone, A; Petrillo, E; Quarantiello, R
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 (2):2937-2940
2007
Conference Title: Applied Superconductivity Conference 2006
108 Scientific Report 2005-2008
Publications
Conference Date: AUG 27-SEP 01, 2006
Conference Location: Seattle, WA
DOI: 10.1109/TASC.2007.900009
Record 13 of 52
Title: Thermal characterization of GdSr2RuCu2Oy-based mixtures in the GdSr2RuO6CuO pseudobinary system
Author(s): Gombos, M; Ciancio, R; Pace, S; Vecchione, A
Source: JOURNAL OF MATERIALS RESEARCH 22 (6):1579-1584 2007
DOI: 10.1557/JMR.2007.0192
Record 14 of 52
Title: Gd-Nd solubility in the (Gd,Nd)-Sr-Ru-Cu-O system
Author(s): Gombos, M; Vecchione, A; Sisti, D; Ciancio, R; Masini, R; Pace, S
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 (2):2965-2968
2007
Conference Title: Applied Superconductivity Conference 2006
Conference Date: AUG 27-SEP 01, 2006
Conference Location: Seattle, WA
DOI: 10.1109/TASC.2007.898958
Record 15 of 52
Title: Electrical resistivity and magnetic behavior of PdNi and CuNi thin films
Author(s): Iannone, G.; Zola, D.; Armenio, A.A.; Polichetti, M.; Attanasio, C.
Source: Physical Review B (Condensed Matter and Materials Physics)|Physical Review B
(Condensed Matter and Materials Physics) vol.75, no.664409-1-6 2007
Record 16 of 52
Title: Two regimes in the magnetic field response of superconducting MgB2
Author(s): Kohen, A; Giubileo, F; Proslier, T; Bobba, F; Cucolo, AM; Sacks, W; Noat, Y;
Troianovski, A; Roditchev, D
Source: EUROPEAN PHYSICAL JOURNAL B 5721-25 2007
DOI: 10.1140/epjb/e2007-00156-9
Record 17 of 52
Title: Thermal propagation of fluxons in two-dimensional Josephson junction arrays
Author(s): Filatrella, G; Girotti, S; Rotoli, G
Source: PHYSICAL REVIEW B 75 (5): 2007
DOI: 10.1103/PhysRevB.75.054510
Record 18 of 52
Scientific Report 2005-2008
109
Publications
Title: Electron spectroscopy study in the NbN growth for NbN/AlN interfaces
Author(s): Lucci, M; Sanna, S; Contini, G; Zema, N; Merlo, V; Salvato, M; Thanh, HN;
Davoli, I
Source: SURFACE SCIENCE 601 (13):2647-2650 2007
Conference Title: International Conference on NANO-Structures Self Assembling
Conference Date: JUL 02-06, 2006
Conference Location: Aix en Provence, FRANCE
DOI: 10.1016/j.susc.2006.11.078
Record 19 of 52
Title: Direct measurement of sheet resistance R-square in cuprate systems: Evidence of a
fermionic scenario in a metal-insulator transition
Author(s): Orgiani, P; Aruta, C; Balestrino, G; Born, D; Maritato, L; Medaglia, PG;
Stornaiuolo, D; Tafuri, F; Tebano, A
Source: PHYSICAL REVIEW LETTERS 98 (3): 2007
DOI: 10.1103/PhysRevLett.98.036401
Record 20 of 52
Title: The periodic Anderson model: Symmetry-based results and some exact solutions
(vol 431, pg 173, 2006)
Author(s): Noce, C
Source: PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS 439 (3):160160 2007
DOI: 10.1016/j.physrep.2006.12.001
Record 21 of 52
Title: Electrical resistivity and magnetic behavior of PdNi and CuNi thin films
Author(s): Iannone, G; Zola, D; Armenio, AA; Polichetti, AM; Attanasio, C
Source: PHYSICAL REVIEW B 75 (6): 2007
DOI: 10.1103/PhysRevB.75.064409
Record 22 of 52
Title: Direct measurement of sheet resistance R square in cuprate systems: evidence of a
fermionic scenario in a metal-insulator transition
Author(s): Orgiani, P.; Aruta, C.; Balestrino, G.; Born, D.; Maritato, L.; Medaglia, P.G.;
Stornaiuolo, D.; Tafuri, F.; Tebano, A.
Source: Physical Review Letters|Physical Review Letters vol.98, no.3036401/1-4 2007
Record 23 of 52
Title: Direct measurement of sheet resistance Rsquare in cuprate systems: evidence of a
fermionic scenario in a metal-insulator transition.
Author(s): Orgiani, P; Aruta, C; Balestrino, G; Born, D; Maritato, L; Medaglia, P G;
Stornaiuolo, D; Tafuri, F; Tebano, A
110 Scientific Report 2005-2008
Publications
Source: Phys Rev Lett 98 (3):036401 2007
Record 24 of 52
Title: EXAFS study of LaNi5 and LaNi4.5Al0.5
Author(s): Palumbo, O; Castellano, C; Paolone, A; Cordero, F; Cantelli, R; Nakamura, Y;
Akiba, E
Source: JOURNAL OF ALLOYS AND COMPOUNDS 433 (1-2):33-36 2007
DOI: 10.1016/j.jallcom.2006.06.068
Record 25 of 52
Title: Local structure characterization of superconducting MgCNi3 prepared by SHS
technique
Author(s): Paolone, A; Castellano, C; Palumbo, O; Cordero, F; Cantelli, R; Martinelli, A;
Ferretti, M
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 454 (1-2):77-81
2007
DOI: 10.1016/j.physc.2007.01.015
Record 26 of 52
Title: The magnetic characterization of a MgB2 superconducting hollow cylinder, at
variable temperatures up to T-c
Author(s): Perini, E; Ginocchio, S; Giunchi, G; Gambardella, U; Pace, S; Matrone, A;
Quarantiello, R; Cavaliere, V; Cavallin, T
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 (2):2730-2733
2007
Conference Title: Applied Superconductivity Conference 2006
Conference Date: AUG 27-SEP 01, 2006
Conference Location: Seattle, WA
DOI: 10.1109/TASC.2007.898272
Record 27 of 52
Title: 0-pi oscillations in nanostructured Nb/Fe/Nb Josephson junctions
Author(s): Piano, S; Robinson, JWA; Burnell, G; Blamire, MG
Source: EUROPEAN PHYSICAL JOURNAL B 58123-126 2007
DOI: 10.1140/epjb/e2007-00210-8
Record 28 of 52
Title: Transport and magnetic properties of strong ferromagnetic pi-junctions
Author(s): Robinson, JWA; Piano, S; Burnell, G; Bell, C; Blamire, MG
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 (2):641-644
2007
Conference Title: Applied Superconductivity Conference 2006
Scientific Report 2005-2008
111
Publications
Conference Date: AUG 27-SEP 01, 2006
Conference Location: Seattle, WA
DOI: 10.1109/TASC.2007.898720
Record 29 of 52
Title: Vortex interaction energy in planar Josephson junction arrays at high density
Author(s): Rotoli, G; Girotti, S; Filatrella, G
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 (2):3537-3540
2007
Conference Title: Applied Superconductivity Conference 2006
Conference Date: AUG 27-SEP 01, 2006
Conference Location: Seattle, WA
DOI: 10.1109/TASC.2007.898912
Record 30 of 52
Title: Role of interband scattering in neutron irradiated MgB2 thin films by scanning
tunneling spectroscopy measurements
Author(s): Di Capua, R; Aebersold, HU; Ferdeghini, C; Ferrando, V; Orgiani, P; Putti, M;
Salluzzo, M; Vaglio, R; Xi, XX
Source: PHYSICAL REVIEW B 75 2007
DOI: 10.1103/PhysRevB.75.014515
Record 31 of 52
Title: Ultrashort lifetime expansion for indirect resonant inelastic x-ray scattering
Author(s): Ament, LJP; Forte, F; van den Brink, J
Source: PHYSICAL REVIEW B 75 (11): 2007
DOI: 10.1103/PhysRevB.75.115118
Record 32 of 52
Title: Magnetic instability in MgB2 monofilamentary tapes
Author(s): Zola, D; Polichetti, M; Martini, L; Pace, S
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 (2):2734-2737
2007
Conference Title: Applied Superconductivity Conference 2006
Conference Date: AUG 27-SEP 01, 2006
Conference Location: Seattle, WA
DOI: 10.1109/TASC.2007.899488
Record 33 of 52
Title: Magnetic relaxation in MgB2 monofilamentary tapes
Author(s): Zola, D; Polichetti, M; Adesso, MG; Martini, L; Pace, S
112 Scientific Report 2005-2008
Publications
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460795-796
2007
Conference Title: 8th International Conference on Materials and Mechanisms of
Superconductivity and High Temperature Superconductors
Conference Date: JUL 09-14, 2006
Conference Location: Dresden, GERMANY
DOI: 10.1016/j.physc.2007.04.034
Record 34 of 52
Title: Point contact spectroscopy on ferromagnetic/superconducting hetero structures
Author(s): Piano, S; Bobba, F; Giubileo, F; De Santis, A; Cucolo, AM
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460886-887
2007
Conference Title: 8th International Conference on Materials and Mechanisms of
Superconductivity and High Temperature Superconductors
Conference Date: JUL 09-14, 2006
Conference Location: Dresden, GERMANY
DOI: 10.1016/j.physc.2007.03.382
Record 35 of 52
Title: Structure, morphology and composition of superconducting Sr2RuO4-Sr3Ru2O7
eutectic crystals
Author(s): Fittipaldi, R; Fusanobori, S; Kittaka, S; Yaguchi, H; Hooper, J; Vecchione, A;
Maeno, Y
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460524-525
2007
Conference Title: 8th International Conference on Materials and Mechanisms of
Superconductivity and High Temperature Superconductors
Conference Date: JUL 09-14, 2006
Conference Location: Dresden, GERMANY
DOI: 10.1016/j.physc.2007.03.178
Record 36 of 52
Title: Transport measurements on Sr2RuO4-Sr3Ru2O7 eutectic crystals
Author(s): Stornaiuolo, D; Born, D; Fittipaldi, R; Vecchione, A; Tafuri, F; Maeno, Y
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460526-527
2007
Conference Title: 8th International Conference on Materials and Mechanisms of
Superconductivity and High Temperature Superconductors
Conference Date: JUL 09-14, 2006
Conference Location: Dresden, GERMANY
DOI: 10.1016/j.physc.2007.03.409
Scientific Report 2005-2008
113
Publications
Record 37 of 52
Title: Nanoscale spatial non-homogeneity of 3D in Delta pi Mg0.9Al0.1B2 single crystals
Author(s): Giubileo, F; Bobba, F; Scarfato, A; Roditchev, D; Zhigadlo, N; Karpinski, J;
Cucolo, AM
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460585-586
2007
Conference Title: 8th International Conference on Materials and Mechanisms of
Superconductivity and High Temperature Superconductors
Conference Date: JUL 09-14, 2006
Conference Location: Dresden, GERMANY
DOI: 10.1016/j.physc.2007.04.136
Record 38 of 52
Title: Temperature evolution of subharmonic gap structures in MgB2/Nb point-contacts
Author(s): Giubileo, F; Bobba, F; Scarfato, A; Piano, S; Aprili, M; Cucolo, AM
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460587-588
2007
Conference Title: 8th International Conference on Materials and Mechanisms of
Superconductivity and High Temperature Superconductors
Conference Date: JUL 09-14, 2006
Conference Location: Dresden, GERMANY
DOI: 10.1016/j.physc.2007.04.137
Record 39 of 52
Title: Local tunneling study of three-dimensional order parameter in the pi band of Aldoped MgB/sub 2/ single crystals
Author(s): Giubileo, F.; Bobba, F.; Scarfato, A.; Cucolo, A.M.; Kohen, A.; Roditchev, D.;
Zhigadlo, N.D.; Karpinski, J.
Source: Physical Review B (Condensed Matter and Materials Physics)|Physical Review B
(Condensed Matter and Materials Physics)24507/1-6 2007
Times Cited: 0
Record 40 of 52
Title: High-velocity instabilities in the vortex lattice of Nb/permalloy bilayers
Author(s): Armenio, AA; Bell, C; Aarts, J; Attanasio, C
Source: PHYSICAL REVIEW B 76 2007
DOI: 10.1103/PhysRevB.76.054502
Record 41 of 52
Title: Zero to pi transition in superconductor-ferromagnet-superconductor junctions
Author(s): Robinson, JWA; Piano, S; Burnell, G; Bell, C; Blamire, MG
114 Scientific Report 2005-2008
Publications
Source: PHYSICAL REVIEW B 76 2007
DOI: 10.1103/PhysRevB.76.094522
Record 42 of 52
Title: Dynamics of defects in alanates
Author(s): Cantelli, R; Palumbo, O; Paolone, A; Jensen, CM; Kuba, MT; Ayabe, R
Source: JOURNAL OF ALLOYS AND COMPOUNDS 446260-263 2007
Conference Title: 10th International Symposium on Metal-Hydrogen Systems,
Fundamentals and Applications
Conference Date: OCT 01-06, 2006
Conference Location: Lahaina, HI
DOI: 10.1016/jjallcom.2007.01.140
Record 43 of 52
Title: H(D)-lattice interactions in single wall carbon nanotubes
Author(s): Palumbo, O; Paolone, A; Cantelli, R; Dettlaff, U; Roth, S
Source: JOURNAL OF ALLOYS AND COMPOUNDS 446376-379 2007
Conference Title: 10th International Symposium on Metal-Hydrogen Systems,
Fundamentals and Applications
Conference Date: OCT 01-06, 2006
Conference Location: Lahaina, HI
DOI: 10.1016/j.jailcom.2006.12.006
Record 44 of 52
Title: Upper critical fields and interface transparency in superconductor/ferromagnet
bilayers
Author(s): Armenio, AA; Cirillo, C; Iannone, G; Prischepa, SL; Attanasio, C
Source: PHYSICAL REVIEW B 76 2007
DOI: 10.1103/PhysRevB.76.024515
Record 45 of 52
Title: Local tunneling study of three-dimensional order parameter in the pi band of Aldoped MgB2 single crystals
Author(s): Giubileo, F; Bobba, F; Scarfato, A; Cucolo, AM; Kohen, A; Roditchev, D;
Zhigadlo, ND; Karpinski, J
Source: PHYSICAL REVIEW B 76 2007
DOI: 10.1103/PhysRevB.76.024507
Record 46 of 52
Title: Nonlinear current-voltage characteristics measured across circular deoxyribonucleic
acid (DNA) molecule bundles
Author(s): Romano, P; Polcari, A; Verruso, B; Colantuoni, V; Saldarriaga, W; Baca, E
Scientific Report 2005-2008
115
Publications
Source: JOURNAL OF APPLIED PHYSICS 102 (10): 2007
DOI: 10.1063/1.2817648
Record 47 of 52
Title: Crystal growth of a lamellar Sr3Ru2O7-Sr4Ru3O10 eutectic system
Author(s): Fittipaldi, R; Sisti, D; Vecchione, A; Pace, S
Source: CRYSTAL GROWTH & DESIGN 7 (12):2495-2499 2007
DOI: 10.1021/cg070180p
Record 48 of 52
Title: Competition between magnetic and superconducting pairing exchange interactions
in confined systems
Author(s): Ying, ZJ; Cuoco, M; Noce, C; Zhou, HQ
Source: PHYSICAL REVIEW B 76 (13): 2007
DOI: 10.1103/PhysRevB.76.132509
Record 49 of 52
Title: Pseudo spin-valves with Al or Nb as spacer layer: GMR and search for spin switch
behaviour
Author(s): Russo, F; Carapella, G; Granata, V; Martucciello, N; Costabile, G
Source: EUROPEAN PHYSICAL JOURNAL B 60 (1):61-66 2007
DOI: 10.1140/epjb/e2007-00329-6
Record 50 of 52
Title: A local field emission study of partially aligned carbon-nanotubes by atomic force
microscope probe
Author(s): Di Bartolomeo, A; Scarfato, A; Giubileo, F; Bobba, F; Biasiucci, M; Cucolo, AM;
Santucci, S; Passacantando, M
Source: CARBON 45 (15):2957-2971 2007
DOI: 10.1016/j.carbon.2007.09.049
Record 51 of 52
Title: High-velocity instabilities in the vortex lattice of Nb/permalloy bilayers
Author(s): Armenio, A.A.; Bell, C.; Aarts, J.; Attanasio, C.
Source: Physical Review B (Condensed Matter and Materials Physics)054502-1-6 2007
DOI: 10.1103/PhysRevB.76.054502
Record 52 of 52
Title: Long-range orbital order in a degenerate-orbital Hubbard model: absence in lowdimensions
Author(s): Noce, C.
Source: New Journal of Physics238 (7 pp.) 2007
116 Scientific Report 2005-2008
Publications
DOI: 10.1088/1367-2630/9/7/238
2006
Record 1 of 46
Title: Identification of the vortex glass phase by harmonics of the AC magnetic
susceptibility
Author(s): Adesso, MG; Polichetti, M; Pace, S
Source: JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 67 (1-3):457-459 2006
Conference Title: 7th International Conference on Spectroscopies in Novel
Superconductors (SNS 04)
Conference Date: JUL 11-16, 2004
Conference Location: Sitges, SPAIN
DOI: 10.1016/j.jpcs.2005.10.010
Record 2 of 46
Title: Investigations of magnetic behavior in various Nb3Sn multifilamentary wires by
means of the 1st and 3rd harmonics of the AC magnetic susceptibility
Author(s): Adesso, MG; Uglietti, D; Abacherli, V; Flukiger, R; Polichetti, M; Pace, S
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 16 (2):1241-1244
2006
Conference Title: 19th International Conference on Magnet Technology
Conference Date: SEP 18-23, 2005
Conference Location: Geneva, ITALY
DOI: 10.1109/TASC.2006.870799
Record 3 of 46
Title: Transition between the Bragg glass and the disordered phase in Nb3Sn detected by
third harmonics of the ac magnetic susceptibility
Author(s): Adesso, MG; Uglietti, D; Flukiger, R; Polichetti, M; Pace, S
Source: PHYSICAL REVIEW B 73 2006
DOI: 10.1103/PhysRevB.73.092513
Record 4 of 46
Title: Excitation gaps in the orbitally degenerate Hubbard model
Author(s): Amendola, ME; Noce, C
Source: JOURNAL OF PHYSICS-CONDENSED MATTER 18 (35):8345-8351 2006
DOI: 10.1088/0953-8984/18/35/019
Scientific Report 2005-2008
117
Publications
Record 5 of 46
Title: Phase diagrams of half-filled 1D and 2D extended Hubbard model within COM
Author(s): Avella, A; Mancini, F
Source: JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 67 (1-3):142-145 2006
Conference Title: 7th International Conference on Spectroscopies in Novel
Superconductors (SNS 04)
Conference Date: JUL 11-16, 2004
Conference Location: Sitges, SPAIN
DOI: 10.1016/j.jpcs.2005.10.040
Record 6 of 46
Title: Spin polarized electron transport in a superconductor/ferromagnet junction with
intermediate barrier strength
Author(s): Carapella, G; Russo, F; Granata, V; Martucciello, N; Costabile, G
Source: SUPERCONDUCTOR SCIENCE & TECHNOLOGY 19 (11):1191-1195 2006
DOI: 10.1088/0953-2048/19/11/017
Record 7 of 46
Title: Enhancement of flux pinning and high-field critical current density in carbon-alloyed
MgB2 thin films
Author(s): Chen, J; Ferrando, V; Orgiani, P; Pogrebnyakov, AV; Wilke, RHT; Betts, JB;
Mielke, CH; Redwing, JM; Xi, XX; Li, Q
Source: PHYSICAL REVIEW B 74 (17): 2006
DOI: 10.1103/PhysRevB.74.174511
Record 8 of 46
Title: Ferromagnetic nanoclusters observed by ac and dc magnetic measurements in
RuSr2GdCu2O8 samples
Author(s): Cimberle, MR; Masini, R; Canepa, F; Costa, G; Vecchione, A; Polichetti, M;
Ciancio, R
Source: PHYSICAL REVIEW B 73 2006
DOI: 10.1103/PhysRevB.73.214424
Record 9 of 46
Title: Effect of electron-phonon interaction on the single-particle spectral properties of the
Hubbard model
Author(s): Citro, R; Cojocaru, S; Marinaro, M
Source: PHYSICA B-CONDENSED MATTER 378-80463-464 2006
Conference Title: International Conference on Strongly Correlated Electron Systems
(SECES 05)
Conference Date: JUL 26-30, 2005
Conference Location: Vienna, AUSTRIA
118 Scientific Report 2005-2008
Publications
DOI: 10.1016/j.physb.2006.01.201
Record 10 of 46
Title: Green's function and excitation spectrum of finite lattices
Author(s): Cojocaru, S; Barsan, V; Ceulemans, A
Source: PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 243 (8):19631977 2006
DOI: 10.1002/pssb.200541484
Record 11 of 46
Title: General conditions for coexisting itinerant ferromagnetism and singlet
superconductivity
Author(s): Cuoco, M; Gentile, P; Noce, C
Source: JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 67 (1-3):157-159 2006
Conference Title: 7th International Conference on Spectroscopies in Novel
Superconductors (SNS 04)
Conference Date: JUL 11-16, 2004
Conference Location: Sitges, SPAIN
DOI: 10.1016/j.jpcs.2005.10.059
Record 12 of 46
Title: Spin-orbital correlations for t(2g) systems in 4d(4) configuration
Author(s): Cuoco, M; Forte, F; Noce, C
Source: PHYSICA B-CONDENSED MATTER 378-801077-1078 2006
Conference Title: International Conference on Strongly Correlated Electron Systems
(SCES 05)
Conference Date: JUL 26-30, 2005
Conference Location: Vienna, AUSTRIA
DOI: 10.1016/j.physb.2006.01.426
Record 13 of 46
Title: Probing spin-orbital-lattice correlations in 4d/sup 4/ systems
Author(s): Cuoco, M.; Forte, F.; Noce, C.
Source: Physical Review B (Condensed Matter and Materials Physics)|Physical Review B
(Condensed Matter and Materials Physics) vol.73, no.994428-1-13 2006
Record 14 of 46
Title: Probing spin-orbital-lattice correlations in 4d(4) systems
Author(s): Cuoco, M; Forte, F; Noce, C
Source: PHYSICAL REVIEW B 73 2006
DOI: 10.1103/PhysRevB.73.094428
Scientific Report 2005-2008
119
Publications
Record 15 of 46
Title: From an insulating to a superfluid pair-bond liquid
Author(s): Cuoco, M; Ranninger, J
Source: PHYSICAL REVIEW B 74 2006
DOI: 10.1103/PhysRevB.74.094511
Record 16 of 46
Title: Interplay of Coulomb interactions and c-axis octahedra distortions in single-layer
ruthenates
Author(s): Cuoco, M; Forte, F; Noce, C
Source: PHYSICAL REVIEW B 74 2006
DOI: 10.1103/PhysRevB.74.195124
Record 17 of 46
Title: Ferromagnetic clusters and superconducting order in
La0.7Ca0.3MnO3/YBa2Cu3O7-delta heterostructures
Author(s): Deen, PP; Yokaichiya, F; de Santis, A; Bobba, F; Wildes, AR; Cucolo, AM
Source: PHYSICAL REVIEW B 74 2006
DOI: 10.1103/PhysRevB.74.224414
Record 18 of 46
Title: Growth of diborides thin films on different substrates by pulsed laser ablation
Author(s): Ferrando, V; Tarantini, C; Manfrinetti, P; Pallecchi, I; Salvato, M; Ferdeghini, C
Source: THIN SOLID FILMS 515 (4):1439-1444 2006
DOI: 10.1016/j.tsf.2006.04.008
Record 19 of 46
Title: Synchronization of Josephson vortices in multi-junction systems
Author(s): Filatrella, G; Pedersen, NF; Wiesenfeld, K
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 437-3865-68
2006
Conference Title: 4th International Conferene on Vortex Matter in Nanostructured
Superconductors (VORTEX IV)
Conference Date: SEP 03-09, 2005
Conference Location: Iraklion, GREECE
DOI: 10.1016/j.physc.2005.12.020
Record 20 of 46
Title: Morphological and structural characterization of GdSr2RuCu2O8 thin film
Author(s): Fittipaldi, R; Nigro, A; Vecchione, A; Gornbos, M; Savo, B; Pace, S
120 Scientific Report 2005-2008
Publications
Source: JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 67 (1-3):613-615 2006
Conference Title: 7th International Conference on Spectroscopies in Novel
Superconductors (SNS 04)
Conference Date: JUL 11-16, 2004
Conference Location: Sitges, SPAIN
DOI: 10.1016/j.jpcs.2005.10.085
Record 21 of 46
Title: Spin-orbital correlations for t/sub 2g/ systems in 4d/sup 4 / configuration
Author(s): Forte, F.; Cuoco, M.; Noce, C.
Source: Physica B|Physica B vol.378-3801077-8 2006
Record 22 of 46
Title: Angular effects of the critical current in Nb/Pd multilayers
Author(s): Gavrilkin, SY; Lykov, AN; Tsvetkov, AY; Vishniakov, YV; Attanasio, C; Cirillo,
C; Prischepa, SL
Source: PHYSICAL REVIEW B 74 (6): 2006
DOI: 10.1103/PhysRevB.74.064509
Record 23 of 46
Title: Role of spin exchange on the coexistence of superconductivity and itinerant
ferromagnetism in a two carrier model
Author(s): Gentile, P; Noce, C; Sigrist, M
Source: PHYSICA B-CONDENSED MATTER 378-80550-551 2006
Conference Title: International Conference on Strongly Correlated Electron Systems
(SECES 05)
Conference Date: JUL 26-30, 2005
Conference Location: Vienna, AUSTRIA
DOI: 10.1016/j.physb.2006.01.248
Record 24 of 46
Title: STS study of the local density of states in MgB2 thin films
Author(s): Giubileo, F; Bobba, F; Roditchev, D; Cucolo, AM
Source: JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 67 (1-3):357-359 2006
Conference Title: 7th International Conference on Spectroscopies in Novel
Superconductors (SNS 04)
Conference Date: JUL 11-16, 2004
Conference Location: Sitges, SPAIN
DOI: 10.1016/j.jpcs.2005.10.113
Record 25 of 46
Scientific Report 2005-2008
121
Publications
Title: Structural and magnetic characterization of GdSr2RuCu2O8 films deposited by d.c.
sputtering
Author(s): Guarino, A; Fittipaldi, R; Nigro, A; Gombos, M; Vecchione, A; Ciancio, R; Pace,
S; Cimberle, MR; Tropeano, M; Zola, D; Polichetti, M
Editor(s): Stutzmann, M
Source: Physica Status Solidi C - Current Topics in Solid State Physics, Vol 3, No 9 3
(9):3073-3076 2006
Conference Title: 4th International Conference on Magnetic and Superconducting
Materials
Conference Date: SEP 05-08, 2006
Conference Location: Agadir, MOROCCO
DOI: 10.1002/pssc.200567041
Record 26 of 46
Title: Recent progress in vortex studies by tunneling spectroscopy
Author(s): Kohen, A; Cren, T; Noat, Y; Proslier, T; Giubileo, F; Bobba, F; Cucolo, AM;
Zhigadlo, N; Kazakov, SM; Karpinski, J; Sacks, W; Roditchev, D
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 437-38145-148
2006
Conference Title: 4th International Conferene on Vortex Matter in Nanostructured
Superconductors (VORTEX IV)
Conference Date: SEP 03-09, 2005
Conference Location: Iraklion, GREECE
DOI: 10.1016/j.physc.2005.12.025
Record 27 of 46
Title: Critical temperature and interface transparency of N/S/N triple layers: theory and
experiment
Author(s): Kushnir, VN; Prischepa, SL; Cirillo, C; Attanasio, C
Source: EUROPEAN PHYSICAL JOURNAL B 52 (1):9-14 2006
DOI: 10.1140/epjb/e2006-00264-0
Record 28 of 46
Title: The periodic Anderson model: Symmetry-based results and some exact solutions
Author(s): Noce, C
Source: PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS 431 (4):173230 2006
DOI: 10.1016/j.physrep.2006.05.003
Record 29 of 46
Title: A basic thermodynamic problem in the dynamic interaction between vortices and
defects
Author(s): Pace, S; Adesso, MG; Filatrella, G; Grimaldi, G; Nigro, A
122 Scientific Report 2005-2008
Publications
Source: PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 437-38258-261
2006
Conference Title: 4th International Conferene on Vortex Matter in Nanostructured
Superconductors (VORTEX IV)
Conference Date: SEP 03-09, 2005
Conference Location: Iraklion, GREECE
DOI: 10.1016/j.physc.2005.12.035
Record 30 of 46
Title: Additional non equilibrium processes in the dynamic interaction between flux quanta
and defects
Author(s): Pace, S; Filatrella, G; Grimaldi, G; Nigro, A; Adesso, MG
Editor(s): Takano, Y; Hershfield, SP; Hirschfeld, PJ; Goldman, AM
Source: Low Temperature Physics, Pts A and B 850873-874 2006
Conference Title: 24th International Conference on Low Temperature Physics (LT24)
Conference Date: AUG 10-17, 2005
Conference Location: Orlando, FL
Record 31 of 46
Title: Monitoring of chemical reactions and point defect dynamics in sodium alanates
Author(s): Palumbo, O; Paolone, A; Cantelli, R; Jensen, CM; Ayabe, R
Source: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS
PROPERTIES MICROSTRUCTURE AND PROCESSING 442 (1-2):75-78 2006
Conference Title: 14th International Conference on Internal Friction and Mechanical
Spectroscopy (ICIFMS-14)
Conference Date: SEP 05-09, 2005
Conference Location: Kyoto, JAPAN
DOI: 10.1016/j.msea.2006.02.209
Record 32 of 46
Title: Fast H-vacancy dynamics during alanate decomposition by anelastic spectroscopy.
Proposition of a model for Ti-enhanced hydrogen transport
Author(s): Palumbo, O; Paolone, A; Cantelli, R; Jensen, CM; Sulic, M
Source: JOURNAL OF PHYSICAL CHEMISTRY B 110 (18):9105-9111 2006
DOI: 10.1021/jp060401m
Record 33 of 46
Title: Comparative study of the phase transition of Li1+xMn2-xO4 by anelastic
spectroscopy and differential scanning calorimetry
Author(s): Paolone, A; Cantelli, R; Scrosati, B; Reale, P; Ferretti, M; Masquelier, C
Source: ELECTROCHEMISTRY COMMUNICATIONS 8 (1):113-117 2006
DOI: 10.1016/j.elecom.2005.10.033
Scientific Report 2005-2008
123
Publications
Record 34 of 46
Title: Doping effects on the phase transition of LiMn(2)O(4)by anelastic spectroscopy and
differential scanning calorimetry
Author(s): Paolone, A; Cantelli, R; Scrosati, B; Reale, P; Ferretti, M; Masquelier, C
Source: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS
PROPERTIES MICROSTRUCTURE AND PROCESSING 442 (1-2):220-223 2006
Conference Title: 14th International Conference on Internal Friction and Mechanical
Spectroscopy (ICIFMS-14)
Conference Date: SEP 05-09, 2005
Conference Location: Kyoto, JAPAN
DOI: 10.1016/j.msea.2006.01.134
Record 35 of 46
Title: An anelastic spectroscopy investigation of carbon nanotubes produced by the highpressure CO method
Author(s): Paolone, A; Palumbo, O; Cantelli, R; Roth, S; Dettlaff, U
Source: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS
PROPERTIES MICROSTRUCTURE AND PROCESSING 442 (1-2):314-318 2006
Conference Title: 14th International Conference on Internal Friction and Mechanical
Spectroscopy (ICIFMS-14)
Conference Date: SEP 05-09, 2005
Conference Location: Kyoto, JAPAN
DOI: 10.1016/j.msea.2006.01.155
Record 36 of 46
Title: Point-contact spectroscopy on RuSr2GdCu2O8
Author(s): Piano, S; Bobba, F; Giubileo, F; Vecchione, A; Cucolo, AM
Source: JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 67 (1-3):384-386 2006
Conference Title: 7th International Conference on Spectroscopies in Novel
Superconductors (SNS 04)
Conference Date: JUL 11-16, 2004
Conference Location: Sitges, SPAIN
DOI: 10.1016/j.jpcs.2005.10.118
Record 37 of 46
Title: Pairing state in the ruthenocuprate superconductor RuSr2GdCu2O8: A point-contact
Andreev reflection spectroscopy study
Author(s): Piano, S; Bobba, F; Giubileo, F; Cucolo, AM; Gombos, M; Vecchione, A
Source: PHYSICAL REVIEW B 73 2006
DOI: 10.1103/PhysRevB.73.064514
124 Scientific Report 2005-2008
Publications
Record 38 of 46
Title: Thickness dependence of pinning mechanisms in granular Nb thin films
Author(s): Prischepa, SL; Montemurro, D; Cirillo, C; Attanasio, C; Salvato, M; Merlo, V;
Lykov, AN; Tsvetkov, AY
Source: SUPERCONDUCTOR SCIENCE & TECHNOLOGY 19 (11):1124-1129 2006
DOI: 10.1088/0953-2048/19/11/006
Record 39 of 46
Title: Resonating bipolarons
Author(s): Ranninger, J; Romano, A
Source: EUROPHYSICS LETTERS 75 (3):461-467 2006
DOI: 10.1209/epl/i2006-10125-6
Record 40 of 46
Title: Critical current oscillations in strong ferromagnetic pi junctions
Author(s): Robinson, JWA; Piano, S; Burnell, G; Bell, C; Blamire, MG
Source: PHYSICAL REVIEW LETTERS 97 2006
DOI: 10.1103/PhysRevLett.97.177003
Record 41 of 46
Title: Modeling study of the dip-hump feature in Bi2Sr2CaCu2O8+delta tunneling
spectroscopy
Author(s): Romano, P; Ozyuzer, L; Yusof, Z; Kurter, C; Zasadzinski, JF
Source: PHYSICAL REVIEW B 73 2006
DOI: 10.1103/PhysRevB.73.092514
Record 42 of 46
Title: Activation energy in La0.7Ca0.3MnO3/YBa2Cu3O7-delta/La0.7Ca0.3MnO3
superconducting trilayers
Author(s): Salvato, M; Bobba, F; Calabrese, G; Cirillo, C; Cucolo, AM; De Santis, A;
Vecchione, A; Attanasio, C
Source: EUROPEAN PHYSICAL JOURNAL B 51 (1):79-85 2006
DOI: 10.1140/epjb/e2006-00200-4
Record 43 of 46
Title: Coexistence of spin polarization and pairing correlations in metallic grains
Author(s): Ying, ZJ; Cuoco, M; Noce, C; Zhou, HQ
Source: PHYSICAL REVIEW B 74 2006
DOI: 10.1103/PhysRevB.74.012503
Record 44 of 46
Scientific Report 2005-2008
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Publications
Title: Field response of metallic grains with magnetic and pairing correlations
Author(s): Ying, ZJ; Cuoco, M; Noce, C; Zhou, HQ
Source: PHYSICAL REVIEW B 74 (21): 2006
DOI: 10.1103/PhysRevB.74.214506
Record 45 of 46
Title: Coexistence of spin polarization and pairing correlations in metallic grains
Author(s): Zu-Jian Ying; Cuoco, M.; Noce, C.; Huan-Qiang Zhou
Source: Physical Review B (Condensed Matter and Materials Physics)|Physical Review B
(Condensed Matter and Materials Physics) vol.74, no.112503-1-4 2006
Record 46 of 46
Title: Field response of metallic grains with magnetic and pairing correlations
Author(s): Zu-Jian Ying; Cuoco, M.; Noce, C.; Huan-Qiang Zhou
Source: Physical Review B (Condensed Matter and Materials Physics)|Physical Review B
(Condensed Matter and Materials Physics) vol.74, no.21214506-1-13 2006
2005
Record 1 of 25
Title: Nonlocal pure spin current injection via quantum pumping and crossed Andreev
reflection
Author(s): Benjamin, C; Citro, R
Source: PHYSICAL REVIEW B 72 (8): 2005
DOI: 10.1103/PhysRevB.72.085340
Record 2 of 25
Title: Morphological and structural study on GdSr2RuCu2O8 melt-textured samples
Author(s): Ciancio, R; Gombos, M; Vecchione, A; Fittipaldi, R; Pace, S
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15 (2):3149-3152
2005
Conference Title: 2004 Applied Superconductivity Conference
Conference Date: OCT 03-08, 2004
Conference Location: Jacksonville, FL
DOI: 10.1109/TASC.2005.848749
Record 3 of 25
Title: Superconducting proximity effect and interface transparency in Nb/PdNi bilayers
Author(s): Cirillo, C; Prischepa, SL; Salvato, M; Attanasio, C; Hesselberth, M; Aarts, J
Source: PHYSICAL REVIEW B 72 2005
126 Scientific Report 2005-2008
Publications
DOI: 10.1103/PhysRevB.72.144511
Record 4 of 25
Title: Atom-molecule coherence in a one-dimensional system.
Author(s): Citro, R; Orignac, E
Source: Phys Rev Lett 95 (13):130402 2005
Record 5 of 25
Title: Atom-molecule coherence in a one-dimensional system
Author(s): Citro, R; Orignac, E
Source: PHYSICAL REVIEW LETTERS 95 (13): 2005
DOI: 10.1103/PhysRevLett.95.130402
Record 6 of 25
Title: Atom-molecule coherence in a one-dimensional system
Author(s): Citro, R.; Orignac, E.
Source: Physical Review Letters|Physical Review Letters vol.95, no.13130402/1-4 2005
Record 7 of 25
Title: Adiabatic-antiadiabatic crossover in a spin-Peierls chain
Author(s): Citro, R; Orignac, E; Giamarchi, T
Source: PHYSICAL REVIEW B 72 (2): 2005
DOI: 10.1103/PhysRevB.72.024434
Record 8 of 25
Title: Renormalization of the electron-phonon interaction in presence of charge
fluctuations
Author(s): Citro, R; Cojocaru, S; Marinaro, M
Source: PHYSICAL REVIEW B 72 (11): 2005
DOI: 10.1103/PhysRevB.72.115108
Record 9 of 25
Title: YBa2Cu3O7-delta/La0.7Ca0.3MnO3 bilayers: Structural and transport properties
Author(s): De Santis, A; Bobba, F; Salvato, M; Cucolo, AM
Source: INTERNATIONAL JOURNAL OF MODERN PHYSICS B 19 (1-3):491-493 2005
Conference Title: 5th International Conference on New Theories, Discoveries and
Applications of Superconductors and Related Materials
Conference Date: JUN 11-16, 2004
Conference Location: Chongqing, PEOPLES R CHINA
Record 10 of 25
Scientific Report 2005-2008
127
Publications
Title: Subharmonic gap structures and Josephson effect in MgB2/Nb microconstrictions
Author(s): Giubileo, F; Aprili, M; Bobba, F; Piano, S; Scarfato, A; Cucolo, AM
Source: PHYSICAL REVIEW B 72 (17): 2005
DOI: 10.1103/PhysRevB.72.174518
Record 11 of 25
Title: Mechanical fragility and tri-dimensional crack structure in NdBaCuO top seeded and
multi-seeded melt-textured samples
Author(s): Gombos, M; Gomis, V; Vecchione, A; Ciancio, R; Fittipaldi, R; Carrillo, AE;
Pace, S; Obradors, X
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15 (2):3137-3140
2005
Conference Title: 2004 Applied Superconductivity Conference
Conference Date: OCT 03-08, 2004
Conference Location: Jacksonville, FL
DOI: 10.1109/TASC.2005.848742
Record 12 of 25
Title: Superconducting vortex profile from fixed point measurements the "Lazy Fisherman"
tunneling microscopy method
Author(s): Kohen, A; Cren, T; Proslier, T; Noat, Y; Sacks, W; Roditchev, D; Giubileo, F;
Bobba, F; Cucolo, AM; Zhigadlo, N; Kazakov, SM; Karpinski, J
Source: APPLIED PHYSICS LETTERS 86 2005
DOI: 10.1063/1.1939077
Record 13 of 25
Title: New perspectives on the Ising model
Author(s): Mancini, F
Source: EUROPEAN PHYSICAL JOURNAL B 45 (4):497-514 2005
DOI: 10.1140/epjb/e2005-00221-5
Record 14 of 25
Title: The extended Hubbard model in the ionic limit
Author(s): Mancini, F
Source: EUROPEAN PHYSICAL JOURNAL B 47 (4):527-540 2005
DOI: 10.1140/epjb/e2005-00357-2
Record 15 of 25
Title: Disorder-driven phase transitions of the large q-state Potts model in three
dimensions
Author(s): Mercaldo, MT; d'Auriac, JCA; Igloi, F
Source: EUROPHYSICS LETTERS 70 (6):733-739 2005
128 Scientific Report 2005-2008
Publications
DOI: 10.1209/epl/i2005-10042-2
Record 16 of 25
Title: Quantum disorder in the periodic Anderson model
Author(s): Noce, C
Source: PHYSICAL REVIEW B 71 (9): 2005
DOI: 10.1103/PhysRevB.71.092506
Record 17 of 25
Title: High-order correlation effects in the two-dimensional Hubbard model
Author(s): Odashima, S; Avella, A; Mancini, F
Source: PHYSICAL REVIEW B 72 2005
DOI: 10.1103/PhysRevB.72.205121
Record 18 of 25
Title: Lattice anomalies in (La,Sr)(2)CuO4 under epitaxial strain probed by polarized X-ray
absorption spectroscopy
Author(s): Oyanagi, H; Saini, NL; Tsukada, A; Naito, M
Source: JOURNAL OF SUPERCONDUCTIVITY 18 (5-6):731-735 2005
Conference Title: International Conference on Nanoscale Heterogeneity and Quantum
Phenomena in Complex Matter
Conference Date: SEP 26-OCT 01, 2004
Conference Location: Rome, ITALY
DOI: 10.1007/s10948-005-0070-6
Record 19 of 25
Title: Comment on "effect of chromium substitution on the lattice vibration of spinel lithium
manganate: A new interpretation of the Raman spectrum of LiMn2O4"
Author(s): Paolone, A; Sacchetti, A; Postorino, P; Cantelli, R
Source: JOURNAL OF PHYSICAL CHEMISTRY B 109 (15):7587-7588 2005
DOI: 10.1021/jp044931z
Record 20 of 25
Title: Point contact study of the superconducting order parameter in RuSr2GdCu2O8
Author(s): Piano, S; Bobba, F; Giubileo, F; Cucolo, AM; Vecchione, A
Source: INTERNATIONAL JOURNAL OF MODERN PHYSICS B 19 (1-3):323-325 2005
Conference Title: 5th International Conference on New Theories, Discoveries and
Applications of Superconductors and Related Materials
Conference Date: JUN 11-16, 2004
Conference Location: Chongqing, PEOPLES R CHINA
Scientific Report 2005-2008
129
Publications
Record 21 of 25
Title: Effect of geometrical symmetry on the angular dependence of the critical magnetic
field in superconductor/normal metal multilayers
Author(s): Prischepa, SL; Cirillo, C; Kushnir, VN; Ilyina, EA; Salvato, M; Attanasio, C
Source: PHYSICAL REVIEW B 72 (2): 2005
DOI: 10.1103/PhysRevB.72.024535
Record 22 of 25
Title: Resonant pairing isotope effect in polaronic systems
Author(s): Ranninger, J; Romano, A
Source: PHYSICAL REVIEW B 71 (18): 2005
DOI: 10.1103/PhysRevB.71.184520
Record 23 of 25
Title: Metal-insulator transition temperature enhancement in La0.7Ca0.3MnO3 thin films
Author(s): Salvato, M; Vecchione, A; De Santis, A; Bobba, F; Cucolo, AM
Source: JOURNAL OF APPLIED PHYSICS 97 (10): Part 1 2005
DOI: 10.1063/1.1898451
Record 24 of 25
Title: Interface transparency and proximity effect in Nb/Cu triple layers realized by
sputtering and molecular beam epitaxy
Author(s): Tesauro, A; Aurigemma, A; Cirillo, C; Prischepa, SL; Salvato, M; Attanasio, C
Source: SUPERCONDUCTOR SCIENCE & TECHNOLOGY 18 (1):1-8 2005
DOI: 10.1088/0953-2048/18/001
Record 25 of 25
Title: Analysis of coupling losses in multifilamentary untwisted BSCCO/Ag tapes through
a.c. susceptibility measurements
Author(s): Zola, D; Gomory, F; Polichetti, M; Strycek, F; Souc, J; Kovac, P; Pace, S
Source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15 (2):2903-2906
2005
Conference Title: 2004 Applied Superconductivity Conference
Conference Date: OCT 03-08, 2004
Conference Location: Jacksonville, FL
DOI: 10.1109/TASC.2005.848629
130 Scientific Report 2005-2008
General Info
CNR-INFM Laboratorio Regionale “SuperMat”
“Superconducting new materials and multilayers: nanostructure, transport and
magnetic propertie”.
c/o Dipartimento di Fisica “E.R. Caianiello”,
Università degli Studi di Salerno
Via Salvador Allende, 84081 Baronissi (SA) - Italy
Tel. +39.089.965369
Fax +39.089.96
http://supermat.physics.unisa.it
some of us…
Scientific Report 2005-2008
131
General Info
You will probably arrive by airplane either at Rome Airport (Leonardo da Vinci) or
at Naples Airport (Capodichino). In both case you will find hereafter the
instructions [A or B, respectively] to reach by train the Salerno Railway Station
(Salerno).
A. From Rome Airport (Leonardo da Vinci) to Salerno
You have the following two steps.
A1. From Rome Airport (Leonardo da Vinci) to Roma Railway Station (Roma
Termini)
You may reach Roma Railway Station (Roma Termini) from the Rome Airport
(Leonardo da Vinci) by train; a taxi is not recommended because of the distance.
The Railway Station is inside the Airport. Take the train to Roma Railway Station
(Roma Termini): the ticket must be bought at the FS office (about 9,00 Euro) and
stamped at the yellow machines before getting on the train. At the same office you
can also buy the ticket from Roma Railway Station (Roma Termini) to Salerno
Railway Station (Salerno).
Remember to stamp the ticket at the yellow machines before getting on the train.
A2. From Roma Railway Station (Roma Termini) to Salerno Railway Station
(Salerno)
132 Scientific Report 2005-2008
General Info
Once in Roma Railway Station (Roma Termini) get a train to Salerno Railway
Station (Salerno).
Remember to stamp the ticket at the yellow machines before getting on the train.
B. From Naples Airport (Capodichino) to Salerno Railway Station (Salerno)
You have the following two steps.
B1. From Naples Airport (Capodichino) to Napoli Railway Station (Napoli
Centrale)
At Naples Airport (Capodichino) you may take the bus (orange bus) just in front of
the Airport entrance (every 15 minutes): the tickets (about 1,00 Euro) are sold
inside the Airport at the newsagents. You have to get down at "Piazza Garibaldi"
(Garibaldi Square) and walk a little bit through the square towards the Napoli
Railway Station (Napoli Centrale). Another possibility is to take a taxi.
B2. From Napoli Railway Station (Napoli Centrale) to Salerno Railway Station
(Salerno)
Once in Napoli Railway Station (Napoli Centrale) get a train to Salerno Railway
Station (Salerno).
Remember to stamp the ticket at the yellow machines before getting on the train.
You can find an on-line official timetable of the Italian Railways (FS) in english at
Official Timetable of Italian Railways (FS) and you can use the name of the
railway stations we quoted above in rounded parentheses (Fiumicino Aeroporto,
Roma Termini, Napoli Centrale, Salerno) as departure or arrival railway stations.
Outside Salerno Railway Station, you can find CSTP BUS with destination
"Università di Salerno" - N. 27. The tickets are sold inside the Railway Station at
newsstand or outside the Railway Station.
Scientific Report 2005-2008
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General Info
134 Scientific Report 2005-2008