¡¡Wellcome!!
Outline
• Current research lines.
• Brief history of the Group
and the context in which it
developed.
• Conclusions.
Who is who in the cake?
In occasion of the 65 birthday of Alberto López García.
Current lines
Zirconia
Ceramics
Ferroelectric
perovskites
Applications of the
Mössbauer Effect
and Magnetism
Magnetism
and magnetic
materials
Physics of
impurities in
Condensed
Matter
Hyperfine
Interactions of
impurities in
solids
Nanostructured
Materials
Research group on Zirconia Ceramics
Dra. Cristina Caracoche
Zirconia (ZrO2) and zirconia based
ceramic materials constitute a vast
ensemble of compounds that can be efficiently
investigated using the TDPAC technique.
Dr. Jorge Martinez
Dr. Agustín Rodríguez
Dra. Patricia Rivas
Dra. Marcela Taylor
Aims: produce stabilized tetragonal and cubic zirconia
based ceramics (powders, films, compacts, glassceramics,
related compounds) and characterize the resulting materials
at nanoscopic scale using the PAC and ME (in compounds
containing Fe) techniques, as a function of temperature up
to 1200C. A PAS equipment will be soon be active.
Study of perovskites and
aurivillius oxides.
Currently investigated materials
Dr. Alberto R. López
García.
Sr1-xBaxHfO3, BaTi1-xHfxO3, Ca1-xSrxHfO3,
SrTi1-xHfxO3, SrTi1-xHfxO3, CaTi1-xHfxO3
x<1
Bi4Srn-3HfxTin1-xO3n+3 with n =3, 4 and x = 0.1, 0.2
Dr. Roberto Alonso.
Dra. Marcela Taylor.
Mr. Martín Falabella.
Aim: Determine material’s properties, some with ferroelectric
characteristics, dependence on composition and temperature:
calorimetric measurements, impedances as a function of
frequency, crystalline and electronic structure, effects of
impurities and defects, phase transitions, hyperfine electric
field gradients, the change of bond types, etc.
Simple calculations based on point charge model and on first
principles theory are performed.
Physics of impurities in Condensed
Matter
Structural, electronic, and magnetic
properties in doped systems:
first principles calculations and
nanoscopic experimental techniques
Aims: *EFG characterization and modeling at impurity sites
in binary oxides.
*Structural and electronic properties of doped
semiconductors.
*Dilute magnetic semiconductors (DMS): structural,
electronic, and magnetic properties in magnetic- and
nonmagnetic-impurity-doped oxide semiconductors.
*Surfaces and clusters in (pure/defect/doped) oxide
semiconductors.
*Applications: Determination of nuclear-quadrupole
moments (Q).
Dr. A.Guillermo
Bibiloni.
Dr. M. Rentería
(Coordinator)
Dr. L.A. Errico
Lic. G.N. Darriba
Mr. E.L. Muñoz
(Diploma Thesis student)
Physics of impurities in Condensed
Matter
Synchrotron radiation techniques
applies to nanostructured systems.
*Catalysis.
*Fundamental properties of
nanoparticles.
*Surfaces and interfaces.
Dr. A.Guillermo
Bibiloni.
Dr. Félix Requejo
(Coordinator)
Dr. José Ramallo López
Lic. L. Giovanetti
Lic. L. Andrini
Laboratory of Applications of the
Mössbauer Effect and Magnetism
Department of Physics, School of Exact Sciences,
National University of La Plata
Promote the academic excellence
in the traditional fields of the
School of Exact Sciences.
Encourage interdisciplinary research
activities, scientific extension and
services in the area of the School.
Bring up graduates able to work in
trans-disciplinary groups, connected
with the local scientific and
technological necessities.
Researchers:
Roberto C. Mercader
Judith Desimoni,
Silvana J. Stewart,
Sonia M. Cotes,
Rodolfo A. Borzi,
Electronic support:
Luis D. Junciel
Technical support:
Flavio R. Sives
PhD Students:
Javier Martínez
Martín D. Mizrahi
Gabriel A. Durán
Academic lines of research:
Nanostructured iron oxide particles
Phase transformations in alloys
Magnetic properties of spinels
Magneto-resistive compounds
Shape-memory alloys
Heterogeneous supported catalysts and
precursor systems.
Aim: dope the pores with Fe oxides to
obtain nanotubes and nanowires.
MCM-41 (Mobile Crystalline Material)
Applied and inter-disciplinary lines:
Loess-paleosols sequences.
Metallurgy.
Clays, soils and iron-bearing minerals.
Archaeology artifacts.
Samples relevant to environmental science.
Group of magnetic
materials
RN3M
2005
National Network of Magnetisn
and Magnetic Materials
Dr. Francisco Sánchez
Magnetic aerogels
SiO2/magnetic nanophase
Isolators and transparent Low
density magnets
Dra. Marcela Fernández van
Raap
Dra. Fabiana Cabrera
Dra. Claudia Rodríguez Torres
Magnetostriction sensors.
Lic. Pedro Mendoza Zélis
Lic. Gustavo Pasquevich
Mössbauer Transmission
Spectroscopy at fixed Doppler
energies.
Nanostructured materials
Aims: studies of
*Nanostructured materials obtained
by mechanical sinthesis.
*Nanoestructured materials
appropriated for hydrogen storage.
*Complex magnetic structures.
Dr. Luis A. Mendoza Zélis.
Dra. Laura Damonte.
Dr. Marcos Meyer.
Lic. Lorena Baum.
Ing. Christian Laborde
Techniques:
MÖSSBAUER SPECTROSCOPY
TDPAC
POSITRON ANNIHILATION SPECTROSCOPY
(Dra. Laura Damonte)
Hyperfine Interactions of
impurities in solids
Aims: Studies of
*Magnetism in thin oxide films,
*Magnetism in intermetallic
compounds,
*Hydrogen in intermetallic
compounds,
*Hafnium-oxygen system,
*Phase transitions in
solids,...
Technique: TDPAC
Dr. Alberto F. Pasquevich.
Dra. Marcela Fernández
van Raap
Dr. Agustin M. Rodríguez.
Perturbed Angular Correlation technique
This technique is appropiated for detecting the
hyperfine interactions at radioactive impurities
(probes) sites .
By Hyperfine Interactions we means the
interactions of the probe nuclear spin with the
surrounding.
Perturbed
Angular
Correlation
equipment of
four detectors
The PAC technique
+ 9/2
requires a radioactive
isotope (probe)
EC
2.83 d
111
In
1/2+
0.12 ns
1
85 ns
245 keV
5/2+
171keV
7/2+
111 Cd
2
estable
The isotope 111Cd,
appropriated for PAC
determinations, results from
the disintegration of 111In
by electron capture.
+
9/2
EC
2.83 d
111
In
1/2+
0.12 ns
1
85 ns
245 keV
5/2+
171keV
7/2+
111 Cd
2
estable
The
probability
of
detecting 2 at an angle 
from the direction of
detection of 1 is measured
as a function of the time t
that the nucleus is in the
intermediate state of the
cascade.
La Plata, August 1964
Uppsala, 1966
Dr. Othaz brough the
electron-gamma
spectrograph gifted for
Uppasala
University,Sweden.
La Plata, 1966
Prof. Dr Othaz
La Noche de los Bastones
Largos
'the night of the long sticks'
"the Night of long knifes."
Beginning of the destruction of the
education at Argentine Universities.
29 de julio de 1966
Ongania´s Time
Our Department of Physics results
benefited. Well recognized theoretical
physicists were incorporated.
For the experimental physics at La
Plata, the shortage of funds made
necessary the use of personal
resources (“piccola cajeta”)
Anyway the Science was preserved
Years later, Prof. Sadosky said:
We believed that, we were doing transcendental things that
the society valorized, and discovered our isolation in the
worst way.
Seeing what came later, with murders and missing
people, we felt that we had been fortunate that night.
The fact had transcendence because an USA
mathematician (Prof. Warren Ambrose from the MIT)
was among the attacked persons.
This prompted the New York Times to publish a
note on the incident, which gave international
notoriety to the situation.
Times of the Civil War (1973-1976)
Those were difficult years but nobody
could imagine what will come later.
How to explain to control patrols and
police barriers that such smoke
substance was not explosive.
The probability of overcoming was bigger if
you talk about liquid Nitrogen than liquid air.
The soldiers and policeman were very clever
for discovering great liars.
Most of them did not know what was the normal
physic state of N2 but all know how looks the air.
The bloody dictatorship
1976 - 1983
The pencil's night
September 1976
C. López Claro,
argentine artist.
Time of IALE (Isotopes far from stability
line) project.
The magnetic Hyperfine field at 140Ce in nickel.
140Xe
was produced by 235U fission
140Ce
is obtained via the - cascade
140
Xe (16 s ) 
140
Cs ( 66 s ) 
140
Ba (12 . 8 d ) 
140
La ( 40 . 2 h ) 
140
Ce ( stable )
Time of IALE (Isotopes far from stability
line) project.
Will they be on the front
cover of the new TDPAC
Herald?
"…something you could
show or not, but
remember that somebody
could visit you to verify if
it is still in your
bookshelf…"
1980, flying to the SLAFES
at Gramado (Brazil).
Synchrocyclotron times:
(1978-1983)
109Ag(
, 2n)111In
E= 56 MeV
Radiation
damage
Alpha
particles
Natural
silver foil
Annealing or melting
required
Acknowledgments: M. Behar and G. García Bermúdez
Sincrociclotron times (Indium jailed in silver)
Impurity-defect interactions
Dose-Rate Dependence of the
Impurity-Defect Interaction in Silver.
L. Thomé and H. Bernas .
Phys. Rev. Lett. 36, 1055–1057 (1976)
Electric field gradients produced by
impurity atoms in a cubic Ag lattice.
F. C. Zawislak, R. P. Livi, L. Amaral,
J. Schaf, and M. Behar.
Hyperfine Interactions, 2, 242,
(1976).
Impurity -impurity interactions
"TDPAC studies of radiation damage in
AgPd and AgPt alloys"
E. Bożek, K. Królas, B. Wodniecka, P.
Wodniecki,
Hyperfine Interactions 4 (1978) 689.
K. Królas, B. Wodniecka, P. Wodniecki,
"Interaction between impurities in Ag
dilute alloys", Hyperfine Interactions
4 (1978) 605.
Charge transfer model for quadrupole
interactions and binding energies of point
defects with 111In/Cd probes in cubic
metals.
Gary S. Collins and Matthew O. Zacate.
Hyperfine Interactions (2004)
Current times
Impurity-defect interactions
1979 – Prof. Erwin Bodenstedt visits for second time
La Plata.
One month before Bibiloni brings two samples implanted in Bonn:
Ag:181Hf
Au:181Hf
Radiation damage,
- PAC
Radiation damage,
e-- PAC
A.F. Pasquevich
F. H. Sánchez
Times of Internal oxidation.
Beginning with the impurity -impurity interaction project we
accidentaly re-discovered the interaction between impurities
and Oxygen in Silver.
The important thing was that we were able to develope an
onw research project.
This discovery give us some international acknowledgement
(not much, of course!). But we were in the herd.
P. Wodniecki, B. Wodniecka, "TDPAC studies of internal AgIn alloy
oxidation", Hyp. Int.12 (1982) 95.
W. Bolse, H. Schröder, P. Wodniecki, M. Uhrmacher, "Innere Oxidation
von Silber-Indium Legierungen", Deutsche Physik. Gesellschaft
Konferenz, Münster 1982.
Splitting: Oxidized and Ionics.
The internal oxidation project produces the first division of the
group:
The short lifetime of indium, conjugated with a manually driven
two detectors equipment required day and night work, and some
members of the lab, because familiar reasons could not work
under such pressure.
The oxidized way:
After all that, "aftereffects were coming".
The study of PAC spectra of internal oxidized indium in
silver, rise the idea of studying normal Indium oxide.
Salomón et al.
Bäverstram and Othaz model.
R (t)
CsF (~ 0,8 ns)
a
Número de coincidencias
The ionic way:
12500
10000
7500
2res = 0.7 ns
5000
2500
t (ns)
0
R(t) spectra of 181Ta in K2ZrF6
b
R (t)
NaI(Tl) (~ 3 ns)
t (ns)
2
4
6
8
Tiempo (ns)
Martinez, 1981
10
12
External War: Malvinas War (1982)
Göttingen 1983
1986, Argentine won the
World Cup of football.
Conclusions:
The group grew and diversify.
Originated at the Hyperfine field has
now many projections in the Solid State
Physics.
…no nos fue tan mal!.
RN3M2
005
National network on magnetism and magnetic materials:
LBT: LOW TEMPERATURE PHYSICS LAB. FCEyN - UBAires
LAL: LASER ABLATION LAB., FI - UBAires
LSA: AMORPHOUS SOLIDS LAB., FI - UBAires
GSM: GROUP OF NANOSTRUCTURED MATERIALS MADE BY
MECHANOSYNTHESIS, FCE - UNLPlata
LAFMACEL: PHYSICAL CHEMISTRY OF CERAMIC ELECTRONIC MATERIALS
LAB., FI - UBAires
LEMöss: MÖSSBAUER SPECTROSCOPY LAB, CAC – CNEAbaires
GMC: CONDENSED MATTER GROUP, CAC – CNEAbaires
GMOxAl: GROUP OF MAGNETISM AND STRUCTURE IN OXIDES AND
ALLOYS, FCE - UNLPlata
HIIS: HYPERFINE INTERACTIONS AT IMPURITY SITES IN SOLIDS, FCE
- UNLPlata
GCM: MATERIALS SCIENCE GROUP, FAMAF - UNCORdoba
LRM-CAB: MAGNETIC RESONANCE GROUP, CAB – CNEAbaires
GTPEM: ELECTRONIC AND MAGNETIC PROPERTIES THEORY GROUP, CAC
– CNEAbaires
LAFISO: SOLID STATE LABORATORY FCyE - UNTucuman
GMM: MAGNETIC MATERIALS GROUP, FCE - UNLPlata