Wednesday 10 July 2013, Strathblane & Cromdale Halls, 16:30-18:30
Poster session B - F-electron systems
P.058 Modulated magnetic states on the border of ferromagnetism in PrPtAl
G Abdul-Jabbar1, A Huxley1, D Sokolov1, C Stock1, F Demmel2 and D Wermeille3
1
University of Edinburgh, UK, 2ISIS Neutron and Muon Spallation Source, UK, 3ESRF, France
On approaching a ferromagnetic quantum critical point there is an inherent instability towards modulated state
formation [1-3] which has recently been interpreted by Karahasanovic et al in terms of "order by disorder" [3].
Predictions based on this and more conventional explanations for modulated state formation will be compared with
detailed observations of the evolution of the magnetic structure as a function of temperature in PrPtAl [4].
On decreasing temperature, PrPtAl, rather than ordering directly into a ferromagnetic state, first passes through
two modulated incommensurate states each characterised by a pair of distinct co-linear ordering vectors. Each pair
of ordering vectors exists over narrow temperature intervals: 5.7-5.2K and 5.2-4.7K respectively [4].
Our discussion will centre on the results of polarised neutron diffraction (SPINS, NCNR), inelastic neutron scattering
(OSIRIS, ISIS), resonant magnetic x-ray scattering (XMaS, ESRF) and bulk thermodynamic measurements taken on
single crystalline PrPtAl.
[1]
[2]
[3]
[4]
G. J. Conduit et al, Phys Rev Lett, 103, 207201 (2009)
V.Chubukov et al, Phys Rev B, 74, 195126 (2006)
U. Karahasanovic et al, Phys. Rev. B, 85, 165111 (2012)
G. Abdul-Jabbar et al (In preparation)
P.059 Comparison of Laue and four-circle single-crystal diffraction in the course of determination magnetic
structures in R2RhIn8 series
P Čermák1, J Rodriguez-Carvajal2, B Ouladdiaf2, M-H Lemee-Cailleau2, K Prokes3, M Boehm2 and P Javorsky1
1
Charles University in Prague, Czech Republic, 2Institute Laue-Langevin, France, 3Helmholtz Zentrum Berlin, Germany
Intermetallic compounds R2RhIn8 (R is a rare earth) are structurally related to a class of Ce-based heavy-fermion
superconductors. Study of their magnetic structure and behavior is important for understanding mechanism of the
unconventional heavy-fermion superconductivity [1]. We have successfully grown single crystals of these
compounds with R = Nd, Tb, Dy, Ho, Er and Tm from the melt in the flux.
We report the evolution of the magnetic structure in this series. All studied compounds exhibit antiferromagnetic
behavior and moreover phase-diagrams of compounds with R = Nd, Tb, Dy and Ho contains additional field-induced
antiferromagnetic phase [2]. Magnetic structures were studied by neutron Laue diffraction technique at the Institute
Laue-Langevin (ILL) in Grenoble on the instruments VIVALDI and CYCLOPS. Laue patterns were indexed and
integrated using software Esmeralda [3] and obtained intensities were treated in the new version of FullProf [4].
Selected compounds were also measured using four-circle diffractometer D10 (ILL) and two-axis diffractometers IN3
(ILL) and E4 (Helmholtz-Zentrum Berlin). These complementary measurements give us valuable comparison and
shows usability of neutron Laue diffraction for magnetic structure determination.
[1]
[2]
[3]
[4]
T. Park et al., Nature 440 (2006) 65
P. Čermák et al., J. Phys.: Condens. Matter 24 (2012) 206005
J. Rodriguez-Carvajal et al., software under development
J. Rodriguez-Carvajal, Physica B 192 (1993) 55
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P.060 Low energy nuclear spin excitations in Ho and Ho-based compounds
T Chatterji1 and N Jalarvo2
1
Institut Laue-Langevin, France, 2Forschungszentrum Juelich, Germany
We have investigated low energy nuclear spin excitations in Ho metal and also in a series of Ho-based compounds,
HoAl2, HoCrO3, HoMnO3, HoNi2Ge2, and HoPd2Ge2 by high-resolution neutron spectroscopy with the back-scattering
neutron spectrometer BASIS at SNS, Oak Ridge National Laboratory. In all cases we detected low energy
excitations at low temperatures and we have interpreted these signals to be due to transitions between hyperfinesplit nuclear levels. In Ho metal and also in HoAl2 we obtained strong and clear signals at E = 26.6 and 25.0 microeV, respectively at T = 3 K both in the energy loss and energy gain sides. The energy of the excitations decreases
with increasing temperature and becomes zero at TC at which temperature the inelastic peaks merge with the central
elastic peak. The temperature dependence of the low-energy excitations was found to follow the order parameter of
the magnetic phase transitions. In two-sublattice magnetic systems like HoCrO3 and also HoMnO3 where the
ordering of Ho ions are only induced by the field of the ordered transition metal ions, the energy of the excitations
stays more or less constant with increasing temperature and the signals get rapidly masked at higher temperatures
by the appearance of strong quasi-elastic scattering presumably due to the fluctuations of the disordered Ho
electronic moments. We plotted the energy of the low energy nuclear excitations as a function of the ordered
electronic magnetic moment and have found an approximate linear relationship.
P.061 Spin wave excitations in the amplitude-modulated magnetic structure of PrNi2Si2
B Fak2, J A Blanco1, J Jensen3, M Rotter4, A Hiess5, D Schmitt6 and P Lejay7
1
University of Oviedo, Spain, 2SPSMS-UMR-E CEA Grenoble, France, 3Niels Bohr Institute, Denmark, 4Max-Planck
Institute for Chemical Physics of Solids, Germany, 5ESS, Sweden, 6ISTerre, CNRS Grenoble, France, 7Institut Neel,
France
In most “equal-moment” systems the magnetic moments saturate at low temperatures, in which case the
longitudinal excitations are quenched, allowing only the presence of transversely polarized spin waves. In contrast,
low-temperature amplitude modulated magnetic structures may support the presence of well-defined longitudinal
excitations, which derive from a modulation of the amplitudes of the moments. PrNi 2Si2 presents a peculiar
magnetic character: it is one of the few examples in nature where the magnetic ions, Pr3+, have a longitudinal
amplitude-modulated magnetic structure below TN = 20 K, which is stable down to 0 K. In this way, the material is
characterized by an Ising-type magnetic structure, where the magnetocrystalline anisotropy confines the magnetic
moments along the c-axis. The magnetic excitations in the low-temperature amplitude-modulated magnetic
structure of PrNi2Si2 have been investigated by inelastic neutron scattering. The dispersions and intensities of both
longitudinal and transverse excitations were measured along the high-symmetry directions. The modulated
magnitude of the ordered moments implies that the longitudinally polarized magnetic excitations are more intense
and dispersive than the usual transverse spin waves. Several well-defined longitudinal amplitude modes are
observed to coexist with the longitudinal phason mode. The experimental results are in good overall agreement with
predictions from the random-phase approximation, using parameters already established from the macroscopic
properties and the paramagnetic excitations. At low energies in the neighborhood of the magnetic zone center, the
magnetic phason appears to hybridize with an unidentified dispersionless mode.
ICNS 2013 International Conference on Neutron Scattering
P.062 Magnetic excitations in YbCo2Si2
A Hannaske1, O Stockert1, K Schmalzl2, D L Quintero Castro3, N Mufti1, C Geibel1 and F Steglich1
1
Max-Planck-Institut für Chemische Physik fester Stoffe, Germany, 2Forschungszentrum Jülich, Jülich Centre for
Neutron Science at Institut Laue-Langevin, France, 3Helmholtz-Zentrum Berlin Germany
The tetragonal heavy-fermion compound YbRh2Si2 is located very close to a quantum critical point (QCP). However,
the direct observation of the spin excitations and quantum critical fluctuations is hindered by the low ordering
temperature TN = 70 mK, the small ordered magnetic moment and the high absorption of neutrons by Rh. One idea
to get a hint how magnetism behaves in YbRh2Si2 is to use isoelectronic YbCo2Si2 as a magnetically well ordered
reference compound. YbCo2Si2 orders antiferromagnetically below TN = 1.7 K with an incommensurate propagation
vector τ1 = (0.25 0.08 1) and changes to a commensurate magnetic structure below TL = 0.9 K with a propagation
vector τ2 = (0.25 0.25 1). Magnetic excitations could be clearly resolved and were studied in the commensurate as
well as in the incommensurate phase in zero field and in applied magnetic field. The dispersions along several
principal directions could be determined. Comparing the dispersions in the commensurate phase with the
incommensurate phase, marked changes occur only in the vicinity of Q = (0 0 1). The results help us to understand
the basic magnetic interactions in YbCo2Si2
P.063 Investigating the polarization dependence of the spin resonance in UPd2Al3 by inelastic neutron scattering
A Hiess1, S Raymond2, K Kaneko3, A Schneidewind4, E Blackburn5, P Steffens6 and G H Lander6
1
ESS AB, Sweden, 2CEA/Grenoble, France, 3JAEA, Tokai, Japan, 4JCNS, FRM2, Germany, 5University of Birmingham,
UK, 6ILL, France
As in the case of high temperature superconductors, the spin dynamics changes on entering the superconducting
state in cerium- and uranium-based intermetallic superconductors: a gap opens at low energies and inelastic
neutron scattering experiments reveal that an increased magnetic intensity is present above the gap, forming in
most cases a sharp inelastic peak (so-called ‘spin resonance peak’). Its momentum space dependence is related to
the symmetry of the superconducting order parameter but its relevance for the paring mechanism is still subject of
debate. The recently observed polarization dependence of the spin resonance in the heavy fermion superconductor
CeCoIn5 (Tc = 2.3K) under magnetic field [S. Raymond et al; PRL 109 (2012) 237210] reveals three excitation
channels. We here report on similar neutron investigations on the AF magnetic superconductor UPd2Al3 (TN = 14K,
Tc = 2K) using the triple-axis spectrometer IN14 at ILL. The magnetic field influences the intensity and the energy of
the spin resonance. Contrary to CeCoIn5, the signal shows no influence by the neutron polarization. The implication
on the theoretical description of the spin resonance will be discussed.
P.064 Magnetic structure and crystalline electric field effect in antiferromagnetic superconductor Pr2Pt3Ge5
S Hwang1, S Lee2, K Lee1, N Sung3, B Cho3, R Kajimoto4 and S Ji4
1
Pohang University of Science and Technology (POSTECH), Korea, 2Korea Atomic Energy Research Institute (KAERI),
Korea, 3Gwangju Institute of Science and Technology (GIST), Korea, 4Comprehensive Research Organization for
Science and Society (CROSS), Japan
The rare-earth ternary intermetallic compounds R2T3X5 (R = rare-earth, T = transition metal, and X= Si, Sn or Ge)
have been well known for their diverse physical properties such as Kondo lattice behavior, heavy fermion behavior,
unusual magnetic order and superconductivity. Amongthe so-called 235 compounds, Pr2Pt3Ge5 single crystal has
been recently reported as a novel magnetic superconductor showing rather high superconducting phase transition
at Tc=7.9 K with successive antiferromagnetic transitions at TN1=4.2 K and TN2=3.4K. We have investigated the
magnetic structure and crystalline electric field (CEF) excitation in this compound by elastic and inelastic neutron
ICNS 2013 International Conference on Neutron Scattering
scattering measurements. The magnetic structure is refined by the group theoretical analysis of powder diffraction
data, and the CEF level scheme is obtained from the inelastic neutron scattering data as well as heat capacity and
magnetic susceptibility data with help of model calculation.
P.065 Magnetic structures in R2TIn8 compounds
P Javorský1, P Čermák1, K Pajskr1, B Ouladdiaf2 and K Prokeš3
1
Charles University in Prague, Czech Republic, 2Institut Laue Langevin, France, 3Helmholtz Zentrum Berlin, Germany
The R2RhIn8 compounds belong to a group of structurally related tetragonal compounds described by a general
formula RmTnX3m+2n (R = rare earth or actinide, T = transition metal, X = In or Ga, m = 1 or 2 and n = 0, 1 or 2).
Unconventional superconductivity was observed in some of the cerium members of this group, what makes rather
interesting also the investigation of their magnetic analogues.
In this work, we present the investigation of magnetic structures in several R2RhIn8 compounds based on single
crystal neutron diffraction and magnetization measurements. Magnetic structures in the studied compounds are
characterized by the propagation vector (1/2 1/2 1/2) for R = Nd, Tb, Dy and Er, (1/2 0 1/2) in Tm2RhIn8 and by
(1/2 0 0) propagation in Ho2RhIn8. The magnetic moments are oriented along the c-axis, except for Er2RhIn8 and
Tm2RhIn8 where the rare-earth moments lie perpendicular to the c-axis. The in-plane moment direction in the erbium
and thulium compounds are in a general agreement with the sign of the crystal field parameters of the R3+ ions. The
results are compared with the magnetic order in related RRhIn5 compounds and the relation of the direction of the
antiferromagnetic coupling with crystallographic parameters is discussed.
P.066 Stability of vibron bound states in Ce(Cu,Al)4 compounds
M Klicpera1, D T Adroja2, P Javorsky1, J W Taylor2 and V Garcia Sakai2
1
Charles University in Prague, Czech Republic, 2ISIS Facility, Rutherford Appleton Laboratory, UK
Abstract unavailable
P.067 Quadrupolar order in UPd3
M D Le1 and K A McEwen2
1
Seoul National University, Korea, 2University College London, UK
The exchange coupling of electronic spins of neighbouring ions to produce magnetic order is a well known
phenomena in solid state physics. In certain compounds, however, the electronic charge distribution may also be
correlated between different ionic sites. These charge distributions may be parameterised by electric multipole
moments, leading one to speak of multipolar order. In UPd3, the successive ordering of different types of
quadrupolar moments leads to a series of four phase transitions at low temperatures.
We present in this paper a model of these phase transitions using the mean-field, random-phase approximation
calculation package McPhase[1] based on the extensive published inelastic neutron scattering data[2]. In
particular we focus on the quasi-cubic site excitations which are modulated by the quadrupolar interactions.
Although these excitations connect the ground state to states with mostly ΔJz=±2, due to the mixing of excited
states into the ground state below the phase transitions, a small dipole transition matrix element exists allowing
their measurement by inelastic neutron scattering.
Finally we explore the possibility to use inelastic neutron scattering to differentiate between dipolar and quadrupolar
interactions. The dispersion in zero field due to the dipolar interactions Jx and Jy are identical to that of the
ICNS 2013 International Conference on Neutron Scattering
quadrupolar interactions Qzx and Qyz. This is not the case in an applied magnetic, however, and whilst the effect is
small, it may be measureable with good enough resolution.
[1]
[2]
M. Rotter, M. D. Le, A. T. Boothroyd and J. A. Blanco, J. Phys. Condens. Matter 24 (2012) 213201
M. D. Le et al., J. Phys. Condens. Matter 24 (2012) 036002
P.068 Observation of charge density wave fluctuations by neutron total scattering in KNi2S2 and KNi2Se2 associated
with heavy fermion behaviour
A Llobet1, J R Neilson2, J Wen2, A V Stier2, L Wu2, J Tao3, Y Zhu3, Z B Tesanovic2, M R Suchomel4, N P Armitage2 and T
M McQueen2
1
Lujan Neutron Scattering Center, Los Alamos National Laboratory, USA, 2Institute for Quantum Matter and
Department of Physics and Astronomy, Johns Hopkins University, USA, 3Brookhaven National Laboratory,
USA, 4Advanced Photon Source, Argonne National Laboratory, USA
Materials with the ThCr2Si2-type structure host myriad examples of many-body physics, including high-temperature
superconductivity and heavy fermion behaviour. In these compounds, the emergence of the collective state
frequently occurs near a magnetic instability, suggesting that magnetic fluctuations underlie the electronic
phenomena. We will provide evidence for similar many-body physics in the structurally related compounds, KNi2S2
and KNi2Se2, but without any signature of a significant magnetic response. From pair-distribution function (PDF)
analysis of temperature-dependent neutron total scattering data, complemented by Rietveld analysis of highresolution synchrotron x-ray diffraction, we observe spatially incoherent charge density wave fluctuations that
disappear on cooling. Accompanying this implied and unusual increase in local symmetry with decreasing
temperature, we find that there is negative thermal expansion and enhancement of the electronic band mass below
T 15 K, with superconductivity emerging below 1 K. These findings, first discovered from PDF analysis of neutron
scattering data, demonstrate that collective electronic phenomena occurs in ThCr2Si2-type materials without direct
proximity to localized magnetism. Furthermore, these results highlight the importance of atomistic structures of
quantum materials, as charge fluctuations and their hybridization may drive the emergence of coherent or manybody electronic states, akin to localized magnetism associated with heavy fermion behaviour.
P.069 Lattice dynamics of the heavy-fermion superconductor CeCu2Si2
M Loewenhaupt1, S Danilkin2, G Deng2, L Capogna3, A Schneidewind4, O Stockert5 and K Hradil6
1
TU Dresden, Germany, 2ANSTO, Australia, 3ILL, France, 4FZJ/FRM2, Germany, 5MPI-CPfS, Germany, 6TU Wien,
Austria
CeCu2Si2 crystallizes in the tetragonal ThCr2Si2-type structure with 5 atoms in the primitive unit cell. It exhibits nonconventional superconductivity driven by low-energy magnetic excitations [1]. The Ce3+ Hund’s rule J=5/2 ground
state is split by the action of the crystalline electric field into 3 doublets, with two excited doublets forming a quasiquartet at around 30 meV [2]. Except for Raman data [3] no information about the lattice dynamics was available
up to date. We therefore performed inelastic neutron scattering at 10 K on a large single crystal on the thermal
triple-axis spectrometers PUMA (FRM II) and TAIPAN (OPAL) to determine the phonon spectra in the [001/110]
plane. The measured dispersion curves will be compared with ab-initio DFT calculations. In addition we could refine
the crystal field level scheme resulting in the observation that the excited quasi-quartet actually consists of two
doublets situated at 30 and 35 meV, respectively [4].
[1]
[2]
[3]
[4]
O. Stockert et al., Nature Physics 7, 119 (2011)
E. A. Goremychkin and R. Osborn, Phys. Rev. B 47, 14280 (1993)
S. L. Cooper et al., Phys. Rev. B 34, 6235 (1986)
M.Loewenhaupt et al., to be published
ICNS 2013 International Conference on Neutron Scattering
P.070 Magnetic properties and magnetocaloric effect in layered NdMn1.7V0.3Si2
M F Md Din1, J Wang2, R Zeng2, M Avdeev3, S Kennedy3, S James Campbell4 and S X Dou2
1
University of Wollongong, Australia, 2Institute for Superconductivity and Electronic Materials, University of
Wollongong, Australia, 3Bragg Institute, ANSTO, Australia, 4School of Physical, Environmental and Mathematical
Sciences, UNSW, Australia
Magnetocaloric effect (MCE) around TC 18 K is found in NdMn1.7V0.3Si2 associated with first order magnetic
transition from antiferromagnetic to ferromagnetic. The magnetic entropy change –ΔSM=12 Jkg/K and adiabatic
temperature change ΔTad = 4.7 K have been determined using magnetization and specific heat measurement.
Neutron investigations indicate that magnetostructural coupling plays a critical role on the magnetocaloric effect.
The study of MCE has become an interesting area of research in the field of magnetic materials as magnetic
refrigerant especially in first order transition material. NdMn1.7V0.3Si2 was be selected for our investigation because
the ferromagnetic (FM) ordering of the Nd sub-lattice offer scope for simultaneous FM ordering of the Mn sub-lattice
.Regarding to the large difference in the atomic radius of Mn (1.24Å) and V (1.34Å), we expect that replacement of
Mn by V in NdMn2Si2 will significantly modify the magnetic states of both the Nd and Mn sub-lattices.
Neutron diffraction study indicates that, above TC, Nd sublattice does not order but Mn sublattice orders
antiferromagnetic (AFil-type) with full moment without any canting. We observe that spontaneous magnetization
decreases with V concentration - indicating that replacement of Mn by V dilutes magnetism in NdMn2-xTixSi2
compounds due to fact that V is nonmagnetic element.
P.071 Interplay of low-energy phonons and magnetic excitations in the Kondo insulator YbB12
K Nemkovskiy1, P Alekseev2, J-M Mignot3, A Ivanov4, M Krisch5, V Lazukov6, P Parshin6, F Iga7, T Takabatake7 and N
Shitsevalova8
1
JCNS FRM II, Forchungszentrum Jülich GmbH, Germany, 2National Research Centre “Kurchatov Institute” &
National Research Nuclear University, Russia, 3Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay, France, 4Institut
Laue-Langevin, France, 5European Synchrotron Radiation Facility, France, 6National Research Centre “Kurchatov
Institute”, Russia, 7Hiroshima University, Japan, 8Frantsevich Institute for Problems of Materials Science, Ukraine
Peculiarities in the lattice dynamics of the Kondo insulator YbB12 have been studied by means of inelastic neutron
and x-ray scattering. Selected phonon modes were traced above and below the characteristic temperature T* 50
K, which corresponds to the opening of the gap in the electron density of states along with a transformation of the
magnetic excitation spectrum. The intensities of some low-energy modes exhibit an anomalous temperature
dependence for q vectors close to the Brillouin zone boundary. This effect is thought to arise from a coupling with
magnetic excitations of the same symmetry, which exist at nearby energies. It is argued that this magnetovibrational coupling could be responsible for the steep temperature crossover existing in YbB12 between the lowtemperature (Kondo insulator) and high-temperature (incoherent spin-fluctuation) regimes.
ICNS 2013 International Conference on Neutron Scattering
P.072 Complex magnetic phase diagram of a geometrically frustrated Sm Lattice: SmPd2Al3 case
J Pospisil1, G Nenert2, S Miyashita3, H Kitazawa4, Y Skourski5, M Divis1, J Prokleska1 and V Sechovsky1
1
Charles University Prague, Czech Republic, 2Institut Laue Langevin, France, 3The University of Tokyo,
Japan, 4National Institute for Materials Science, Japan, 5Dresden High Magnetic Field Laboratory, HelmholtzZentrum Dresden Rossendorf, Germany
SmPd2Al3 represents an example of Sm magnetism with a complex magnetic phase diagram where four consecutive
magnetic phase transitions (MPT) at 3.4, 3.8, 4.3 and 12.5 K have been observed. The complexity of magnetism in
this compound is caused by specific features of the Sm3+ ion, namely by nearness of the ground-state multiplet J =
5/2 and the first excited multiplet J = 7/2 in conjunction with strong crystal field influence. We have established a
magnetic phase diagram of this compound. Since the magnetic characteristics had been obtained from bulk
measurements detailed information regarding the magnetic structure of each magnetic phase was lacking and
neutron diffraction was highly desirable. To reduce the problem of the strong neutron absorption by the natural Sm
isotope we performed the experiment at the ILL Grenoble D9 diffractometer with the hot source providing neutrons of
a short wavelength (l = 0.5 Å). We will report on the temperature evolution of the magnetic reflections in comparison
with bulk data. The (5/3 5/3 0) and (4/3 1/3 0) reflections emerged at 12.5 K which is in good agreement with
bulk magnetic and specific-heat data. The maximum of the intensity was found at 4.3 K, where the second MPT
occurs. Further lowering temperature leads to gradual suppression of these reflections and emerging new magnetic
reflections, which reflect formation of another magnetic structure. This observation classifies the SmPd2Al3
compound as a magnetically frustrated system. The complex magnetic behavior of this material is further illustrated
by kinetic effects of the magnetization inducing rather complicated magnetic structure with various metastable
states.
P.073 Evidence for three fluctuation channels in the spin resonance of the unconventional superconductor CeCoIn 5
S Raymond1, K Kaneko2, A Hiess3, P Steffens4 and G Lapertot1
1
CEA, France, 2Japan Atomic Energy Agency, Japan, 3European Spallation Source, Sweden, 4Institut Laue Langevin,
France
The spin resonance is a ubiquitous magnetic excitation that appears in many unconventional superconductors:
cuprates, iron pnictides, and chalcogenides and heavy fermion systems. This mode is observed in inelastic neutron
scattering (INS) experiments below the superconducting transition temperature. It appears at the wave vector for
which the superconducting gap changes sign and at an energy below the one of the superconducting gap. While
there is no consensus on the origin of such an excitation and its relevance to the pairing mechanism, this feedback
effect of superconductivity on the magnetic excitation spectrum provides important information about the
superconducting state.
Polarized inelastic neutron scattering under a magnetic field was used to get a microscopic insight into the spin
resonance of the heavy fermion superconductor CeCoIn5 (Tc=2.3 K). It is found that the spin resonance splits under
magnetic field, a feature expected for Pauli limited superconductors. However this splitting involves only one part of
the magnetic response, which has a chiral nature. The remaining spectral weight consists of a nonchiral contribution
that appears at the same energy as the lowest of the Zeeman split peaks. The spin resonance in CeCoIn5 is thus a
composite excitation which contains, under magnetic field, three excitation channels. This result puts strong
constraints on theoretical descriptions of spin resonances.
[1]
Physical Review Letter 109, 237210 (2012)
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P.074 Neutron depolarisation imaging of the kondo cluster glass formation in CePd 1-xRhx
P Schmakat1, M Schulz2, M Brando3, C Geibel3, C Pfleiderer4 and P Böni4
1
Technische Universität München, Germany, 2Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II),
Germany, 3Max-Planck-Institut für Chemische Physik fester Stoffe, Germany, 4Technische Universität München,
Germany
At the neutron imaging beam line ANTARES at FRM II, Munich, we have recently developed the Neutron
Depolarisation Imaging (NDI) technique. The NDI method, which is a combination of neutron radiography and
polarisation analysis, allows mapping of variations of magnetic properties over a sample on a length scale of about
300 µm. These may, for instance, result from variations of the chemical composition of the sample. A closed cycle
cryostat in combination with a 3He/4He dilution insert has enabled us to reach temperatures as low as 75 mK in
such measurements. A study on the metallurgically inhomogenous Kondo lattice system CePd1-xRhx has been
performed to demonstrate the potential of the NDI technique at such low temperatures. Additional magnetic fields
applied at the sample position allowed us to identify spin glass behaviour in CePd1-xRhx at low temperatures for
moderate Rh concentration x. In our contribution we will discuss the experimental technique as well as its
application to disordered, ferromagnetic materials that undergo quantum phase transitions.
[1]
[2]
[3]
[4]
[5]
M. Schulz et al., Nucl. Instr. and Meth. in Phys. Res. A, 605, 2009, p.43-46
M. Schulz et al., Physica B, Vol. 406, 2011, p.2412-2414
C. Pfleiderer et al., J. Low Temp. Phys., Vol. 161, 2010, p.167-181
T. Westerkamp et al., Phys. Rev. Lett., Vol. 102, 2009, 206404.
J. G. Sereni et al., Phys. Rev. B, Vol. 75, 2007, 024432
P.075 Transition from three-dimensional to two-dimensional magnetic order at high magnetic field in singlecrystalline CeCu2Ge2
A Schneidewind1, E Faulhaber2, M Loewenhaupt3, M Deppe4 and O Stockert4
1
JCNS Forschungszentrum Jülich, Germany, 2TU München, FRM II, Germany, 3Institut für festkörperphysik, TU
Dresden, Germany 4MPI-CPfS Dresden, Germany
Abstract unavailable
P.076 Magnetic field dependence of the antiferromagnetic order in CeCu2(Si1-xGex)2
A Schneidewind1, P Geselbracht2, J Arndt3, E Faulhaber2, U Witte4, A Hoser4, N Stüßer4, M Deppe3 and O Stockert3
1
JCNS Forschungszentrum Jülich, Germany, 2TU München, FRM II, Germany, 3MPI-CPfS Dresden, Germany,
Helmholtz-Zentrum Berlin, Germany
4
Substituting germanium for silicon, the intermetallic system CeCu2(Si1-xGex)2 can be tuned from the heavy-fermion
superconductor CeCu2Si2 to the antiferromagnet CeCu2Ge2. The transition temperatures and ordered magnetic
moments increase with x, while the magnetic structures in CeCu2(Si1-xGex)2 seem to be similar to those in CeCu2Si2.
CeCu2(Si0.55Ge0.45)2 orders antiferromagnetically at a rather high Néel temperature of TN = 3.1 K with an ordered
magnetic moment of m = 0.75 muB. Three magnetically ordered phases are observed in zero magnetic field, two of
them being clearly incommensurate and a low temperature phase below 1.5 K most likely being a lock-in phase
with a no further change in the propagation vector. The zero-field magnetic structure has been revealed by neutron
diffraction [1]. Changes of the magnetic structure in CeCu2(Si0.55Ge0.45)2 with field are expected from heat capacity
measurements above B = 6 T [2] as well as from the analogy to CeCu2Si2 [3].
ICNS 2013 International Conference on Neutron Scattering
Here we present single crystal neutron diffraction on E6, HZB, to study the magnetic field dependence of the
magnetic order in CeCu2(Si0.55Ge0.45)2 combined with magneto-caloric measurements at similar temperatures. In
contrast to the expectation, no magnetic intensity has been detected above 2T in the lock-in-phase at lowest
temperatures, while it survives up to 4.4 T with changing magnetic moment direction at higher temperature.
[1]
[2]
[3]
E. Faulhaber et al., J. Mang. Magn. Mater. 272-276, 44 (2004)
N. Oeschler, Dissertation Dresden 2003
E. Faulhaber et al., BENSC Experimental Report PHY-01-1547 (2004)
P.077 Magnetic structures of HoRh2Si2 having successive component-separated magnetic transitions
T Shigeoka1, H Cao2, T Fijiwara1 and Y Uwatoko3
1
Yamaguchi University, Japan, 2Oak Ridge National Laboratory, USA, 3University of Tokyo, Japan
The ternary compound HoRh2Si2, which is crystallized in the tetragonal ThCr2Si2-type structure, orders
antiferromagnetically and shows successive magnetic transitions at TN1=29 K, Tt=27 K and TN2=12 K. Previous
magnetic studies have suggested that the transitions at TN1 and TN2 are so called “component-separated magnetic
transitions”. Such transitions often appear in frustration systems. The geometrical frustration of exchange
interactions between magnetic ions is responsible for most of this-type transitions. In the case of HoRh2Si2,
however, no geometrical frustration is considered. So the origin for the transitions is very interesting. Then neutron
diffraction experiments on a HoRh2Si2 single crystal compound were performed using a triple axis spectrometer and
a four circle diffractometer in order to determine the magnetic structures as the first step. Antiferromagnetic
structures determined are as follows; For T< TN2, the propagation vector k1= (0, 0, 1) with magnetic moments tilted
from the c-axis by 26 degree. For TN2<T< Tt, the propagation vector k1 = (0, 0, 1) with magnetic moment parallel to
the c-axis; the tilt angle changes to zero above TN2. For Tt <T< TN1, the propagation vector becomes k2 = (1/2, 1/2,
1/2) with magnetic moments along the c-axis. Above TN2, diffuse scattering, which suggests that the ab-component
of magnetic moments is disordered, is observed around the (1 0 0) antiferromagnetic reflection. We believe this
compound is a frustration system. The origin will be discussed.
P.078 Neutron scattering studies of the non-centrosymmetric antiferromagnets CePdSi3 and CePtSi3
M Smidman1, D Adroja2, M M Koza3, C Ritter3, R Singh4, M Lees5, E Goremychkin2, S Rols3, D Paul5 and G
Balakrishnan5
1
Department of Physics, University of Warwick, 2ISIS facility, UK, 3Institut Laue Langevin, France, 4Indian Institute of
Science Education and Research Bhopal, India, 5University of Warwick, UK
Inelastic neutron scattering (INS) and neutron diffraction measurements have been carried out on the heavy fermion
antiferromagnets CePdSi3 and CePtSi3. These are isostructural to the unconventional non-centrosymmetric
superconductors CeCoGe3, CeRhSi3 and CeIrSi3. Both compounds exhibit two magnetic transitions. CePdSi3 orders
at TN1 = 5.2 K and undergoes a second transition at TN2 = 3 K, whilst for CePtSi3, TN1 = 4.8 K and TN2 = 2.4 K.
Low energy INS measurements have revealed spin wave excitations below TN1 and quasielastic scattering above the
ordering temperature. The temperature dependence of the quasielastic linewidth has been determined and
compared to other members of the CeTX3 (T = transition metal, X = Si or Ge) family. INS studies have also been
used to examine the crystal-field (CEF) excitations. Well defined CEF excitations have been observed at 4.9 meV in
CePtSi3 and 5.6 meV and 32 meV in CePdSi3, with linewidths narrower than those measured in the superconducting
analogues. This indicates local moment magnetism with relatively weak hybridization between the cerium 4f
electrons and the conduction band.
Neutron diffraction studies on CePtSi3 reveal magnetic Bragg peaks at 1.2 K, which change in position above TN2.
This suggests that the propagation vector changes between the two magnetic phases.
ICNS 2013 International Conference on Neutron Scattering
P.079 Spin fluctuations and Lifshitz transition in UGe2 probed by Larmor neutron diffraction under pressure
D Sokolov and A Huxley
University of Edinburgh, UK
We present high resolution measurements of the lattice constants of ferromagnetic superconductor UGe2 under
pressure probed by a novel technique that utilizes Larmor precession of polarized neutrons to surpass the resolution
of conventional scattering methods by an order of magnitude [1]. At low temperature UGe2 is ferromagnetic up to
critical pressure pc but superconductivity is peaked at a lower pressure px coinciding with a less well understood
transition within the ferromagnetic state [2]. We report a new phase line in the (p,T) phase diagram at temperatures
above that at which the magnetization transition is observed. The line is inferred from the onset of anisotropic
change of the lattice expansion at p< px. Our results suggest that the magnetization transition may be driven by the
collapse of the Kondo resonance near px accompanied by the topological Fermi-surface transition [3]. Both effects
could be pre-requisite for unconventional superconductivity in 4f and 5f heavy fermion compounds [4].
[1]
[2]
[3]
[4]
D. A. Sokolov, et al., J. Phys.: Conf. Series, 271, 012085 (2011)
S. S. Saxena, et al., Nature 406, 587 (2000)
I. M. Lifshitz, Sov. Phys. JETP 11, 1130 (1960)
D. A. Sokolov, et al., Phys. Rev. Lett. submitted (2012)
P.080 Magnetic structure of PrPd3
H S Suzuki1, N Terada1, K Kaneko2 and N Metoki2
1
National Institute for Materials Science, Japan, 2Japan Atomic Energy Agency, Japan
PrPd3 with AuCu3-type structure show a complex magnetic phase diagram. The specific heat shows double peaks at
TN = 0. 88 K and 0.77 K, which are relatively low compared with the Curie-Weiss temperature TCW 17 K. The
temperature of the peak at higher temperature is increased but another decreased with the magnetic field. A large
tail above TN in the specific heat is also observed. Considering no geometric frustrations in the simple cubic
structure of the Pr site, these behavior suggest a competition of inter-site interactions. The magnetic field
dependence of the peak at higher temperature, which is typical in the quadrupole ordering system, also suggests an
importance of the multipole effect arising from the crystalline electric field ground state.
We have investigated the multipole effect using the single crystal by specific heat, magnetic susceptibility, ultrasonic and also neutron scattering measurements. In this report, we focus on the magnetic structure and its
transition. We have found first the 1st transition of the magnetic phase at 0.5 K. The propagation vector observed in
the neutron scattering is changed from the incommensurate to commensurate one. We will discuss the complex
magnetic phase based of the multipole effect.
P.081 Inelastic neutron scattering study on cubic Pr compounds with doublet gamma-3 ground state
H S Suzuki1, N Terada1, K Kaneko2, N Metoki2, T Onimaru3, R-M Galera4, M Amara4 and L-P Regnault5
1
National Institute for Materials Science, Japan, 2Japan Atomic Energy Agency, Japan, 3Hiroshima University,
Japan, 4Neel Institute, CNRS, France, 5CEA-Grenoble, France
Cubic compound including non-Kramers rare-earth ion are of special interest since a non-magnetic doublet
Gamma-3 ground state, i.e. with degrees of freedom of not magnetic dipole but electrical quadupole and magnetic
octupole, is possibly realized due to a crystalline-electric-field (CEF). We have investigated the CEF excitation in the
cubic Pr compounds with the Gamma-3 ground state and the triplet Gamma-4 1st excited state, such as PrMg3,
PrPb3 and PrAg2In by the inelastic neutron scattering. The common peculiar feature of the observed spectra in the
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paramagnetic phase for those compounds is that the excitation spectrum of the Gamma-3 - Gamma-4 transition
consists of two peaks, resulting in the two branches in dispersion relation. While one branch shows a relatively
strong q-dependence, the other branch is almost dispersionless and its width is relatively broadened. The two
branches in the paramagnetic phase can not be explained by considering only usual crystal field model because
the crystallographic sites of Pr ion is only one. A theoretical study has shown an appearance of the double peak
structure of the inelastic spectrum in term of the doublet degeneracy of the ground state and multipole exchange
interactions under cubic point symmetry. In this conference, we will show the results for those compounds and
discuss the origin of this anomaly in the spectra of the inelastic neutron excitation.
P.082 Magnetic order in Tm3Cu4X4 (X = Si, Ge, Sn) compounds
A Szytuła1, S Baran1, D Kaczorowski2, A Hoser3 and A Szytuła1
1
Jagiellonian University, Poland, 2Institute of Low Temperature and Structure Research PAS, Poland, 3HelmholtzZentrum Berlin für Materiailen und Energie GmbH, Germany
The Tm3Cu4X4 compounds crystallize in the orthorhombic crystal structure for X = Si and Ge (space group Imma) and
the monoclinic one for X = Sn (space group C2/m). The properties of these compounds were studied by magnetic,
specific heat and electrical resistivity measurements and neutron diffraction. The analysis of the experimental data
revealed no magnetic ordering in Tm3Cu4Si4 and antiferromagnetic order below TN = 2.8 K for remaining compounds.
Below the Néel temperature the additional phase transition at Tt = 2.1 K (X = Ge) and 1.8 K (X = Sn) is detected.
The neutron diffraction data revealed the complex magnetic order. Below TN the Tm magnetic moment at the 2d site
in Tm3Cu4Ge4 and the 2c one in Tm3Cu4Sn4 form a collinear magnetic order described by the propagation vector k =
(0, ½, 0) and k = (0, 0, ½), respectively. Below Tt the Tm moments at the 4c site (X = Ge) and the 4d one (X = Sn)
form a modulated incommensurate structure described by the propagation vector k = (¼, 0, kz) for X = Ge and k =
(¼, ky, 0) for X = Sn, with kz and ky being close to 0.5. The Tm moments are close to 7.0 μB and they are parallel to
c-axis for the 2d site and b-axis for the 4d site (X = Ge) and to b-axis (2c) and c-axis (4d) for X = Sn. These data are
compared with the data for isostructural R3Cu4X4 compounds.
This research project has been supported by the European Commission under the 7th Framework Programme
through the Key Action Strengthening the European Research Area, Research Infrastructures, Contract no: 226507
(NMI13) and the Ministry of Science and Higher Education in Poland under Grant no. N N202 201 039.
P.083 Field-induced changes in the magnetic state and crystal structure of Ho5Pd2 magnetocaloric compound
P Terent'ev1, A Gubkin1, E Sherstobitova1, A Hoser2, S Belyaeva3 and N Baranov4
1
Institute for metal physics, UB RAS, Russia, 2Helmholtz-Zentrum Berlin, Germany, 3Ural Federal University,
Russia, 4Institute of Natural Sciences, Ural Federal University, Russia / Institute for metal physics, UB RAS, Russia
The binary rare-earth intermetalliс compound Ho5Pd2 crystallizes in the cubic Dy5Pd2-type structure (SG Fd3m) and
exhibit a giant magnetocaloric effect at low temperatures [1]. In this work the neutron powder diffraction (NPD)
study in applied magnetic fields up to 50 kOe has been performed in order to reveal the effect of the magnetic field
on the magnetic state and crystal structure of Ho5Pd2. It has been found that a long-range magnetic order does not
develop in this compound with cooling down to 2 K. Instead, the broad diffuse maxima were observed to appear in
the low Q-range around 30 K. These maxima can be ascribed to the incommensurate antiferromagnetic (AF) spin
clusters persisting down to 2 K, which is in agreement with results of our preliminary magnetic measurements.
Application of an external magnetic field up to 10 kOe results in the suppression of a short-range AF order and
formation of the field-induced long-range ferromagnetic order, which agrees well with the field dependence of the
magnetization measured on a polycrystalline sample [1]. Moreover, new additional narrow Bragg reflections were
found to appear at the NPD pattern along with developing ferromagnetic order. These reflections can’t be indexed
within the Fd3m space group and simple k = 000 ferromagnetic structure. These changes in the neutron powder
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diffractogram are suggested to result from the rhombohedral distortions of the crystal lattice due to the
ferromagnetic ordering caused by application of the magnetic field. This work was supported by the program of the
Ural Branch of RAS (project No. 12-T-2-1012) and RFBR (Grant No 12-02-31137).
P.084 Magnetism in UCo0.88Ru0.12Ge studied by polarized neutrons
M Vališka1, J Pospíšil1, G Nénert2, A Stunault2, K Prokeš3 and V Sechovský1
1
Charles University, Czech Republic, 2Institut Laue Langevin, France, 3HZB Berlin, Germany
UCoGe is an archetype of coexisting the 5f-electron ferromagnetism (TC 3 K) and superconductivity (TSC 0.6 K)
in ambient pressure. The low spontaneous magnetic moment of UCoGe (0.03μB/f.u) indicates nearness of
ferromagnetic instability. We have prepared a series of UCo1-xRuxGe polycrystals in order to study development of
magnetism and superconductivity. The Ru doping leads to an initial sharp increase of the Curie temperature up to
the maximum of TC = 8.5 K for x = 0.12 and suppression of superconductivity.
Further increase of Ru content yields gradual decrease of TC towards the ferromagnetic quantum critical point at
x ≈ 0.3. We have grown the UCo0.88Ru0.12Ge single crystal and observed that it exhibits strong magnetocrystalline
anisotropy analogous to UCoGe and a spontaneous easy-axis magnetization considerably higher than found in the
parent compound. To see the microscopic background of these findings we performed a polarized neutron
diffraction experiment at D3 in ILL. In contrast to the antiparallel orientation of the Co and U moments in UCoGe (in
12 T μCo=-0.27μB, μU =μU,L+μU,S=0.49-0.17=0.32μB) we have found that the Co and U moments are parallel in
UCo0.88Ru0.12Ge (in 9T μCo=0.069μB, μU=μU,L+μU,S=0.457-0.20=0.257μB). This stands behind the magnetization
increase with Ru doping which evokes a question whether the magnetic state of Co can be a critical parameter for
presence of superconductivity in U(Co,Ru)Ge compounds.
ICNS 2013 International Conference on Neutron Scattering