24 research outputs found
Crystalline Electric Field and Kondo Effect in SmOs4Sb12
Our ultrasound results obtained in pulsed magnetic fields show that the
filled-skutterudite compound SmOsSb has the quartet
crystalline-electric-field ground state. This fact suggests that the multipolar
degrees of freedom of the quartet play an important role in the
unusual physical properties of this material. On the other hand, the elastic
response below 20 T cannot be explained using the localized
4-electron model, which does not take into account the Kondo effect or
ferromagnetic ordering. The analysis result suggests the presence of a
Kondo-like screened state at low magnetic fields and its suppression at high
magnetic fields above 20 T even at low temperatures.Comment: 4 pages, 4 figure
Elastic Response in the Dilute non-Kramers System YPrIrZn
Ultrasonic investigations of the single-site quadrupolar Kondo effect in
diluted Pr system YPrIrZn are reported. The
elastic constant is measured down to ~40 mK using
ultrasound for the dilute system YPrIrZn and the
pure compound YIrZn. We found that the elastic constant
of the Pr-dilute system exhibits a logarithmic temperature
dependence below ~0.3 K, where non-Fermi-liquid (NFL) behavior in the
specific heat and electrical resistivity is observed. This logarithmic
temperature variation manifested in the -symmetry quadrupolar
susceptibility is consistent with the theoretical prediction of the quadrupolar
Kondo effect by D. L. Cox. On the other hand, the pure compound
YIrZn without -electron contributions shows nearly no change in
its elastic constants evidencing negligible phonon contributions. In addition,
clear acoustic de Haas-van Alphen (dHvA) oscillations in the elastic constant
were detected for both compounds on applying magnetic field. This is mainly
interpreted as contribution from the Fermi surface of YIrZn.Comment: 9 pages, 4 figures, Proceedings of J-Physics 2019 International
Conferenc
Magnetoelectric effect and phase transitions in CuO in external magnetic fields
Apart from being so far the only known binary multiferroic compound, CuO has
a much higher transition temperature into the multiferroic state, 230 K, than
any other known material in which the electric polarization is induced by
spontaneous magnetic order, typically lower than 100 K. Although the
magnetically induced ferroelectricity of CuO is firmly established, no
magnetoelectric effect has been observed so far as direct crosstalk between
bulk magnetization and electric polarization counterparts. Here we demonstrate
that high magnetic fields of about 50 T are able to suppress the helical
modulation of the spins in the multiferroic phase and dramatically affect the
electric polarization. Furthermore, just below the spontaneous transition from
commensurate (paraelectric) to incommensurate (ferroelectric) structures at 213
K, even modest magnetic fields induce a transition into the incommensurate
structure and then suppress it at higher field. Thus, remarkable hidden
magnetoelectric features are uncovered, establishing CuO as prototype
multiferroic with abundance of competitive magnetic interactions.Comment: 26 pages, 5 figure
Strong anisotropy of electron-phonon interaction in NbP probed by magnetoacoustic quantum oscillations
In this study, we report on the observation of de Haas-van Alphen-type
quantum oscillations (QO) in the ultrasound velocity of NbP as well as `giant
QO' in the ultrasound attenuation in pulsed magnetic fields. The difference of
the QO amplitude for different acoustic modes reveals a strong anisotropy of
the effective deformation potential, which we estimate to be as high as
for certain parts of the Fermi surface. Furthermore, the
natural filtering of QO frequencies and the tracing of the individual Landau
levels to the quantum limit allows for a more detailed investigation of the
Fermi surface of NbP as was previously achieved by means of analyzing QO
observed in magnetization or electrical resistivity.Comment: 5 figure
Multiferroic spin-superfluid and spin-supersolid phases in MnCr2S4
Spin supersolids and spin superfluids reveal complex canted spin structures
with independent order of longitudinal and transverse spin components. This
work addresses the question whether these exotic phases can exhibit spin-driven
ferroelectricity. Here we report the results of dielectric and pyrocurrent
measurements of MnCr2S4 as function of temperature and magnetic field up to 60
T. This sulfide chromium spinel exhibits a Yafet-Kittel type canted spin
structure at low temperatures. As function of external magnetic field, the
manganese spins undergo a sequence of ordering patterns of the transverse and
longitudinal spin components, which can be mapped onto phases as predicted by
lattice-gas models including solid, liquid, super-fluid, and supersolid phases.
By detailed dielectric and pyrocurrent measurements, we document a zoo of
multiferroic phases with sizable ferroelectric polarization strongly varying
from phase to phase. Using lattice-gas terminology, the title compound reveals
multiferroic spin-superfluid and spin-supersolid phases, while the
antiferromagnetic solid is paraelectric.Comment: 14 pages including 5 figure
Magnetoelectric effect and phase transitions in CuO in external magnetic fields
Apart from being so far the only known binary multiferroic compound, CuO has a much higher transition temperature into the multiferroic state, 230 K, than any other known material in which the electric polarization is induced by spontaneous magnetic order, typically lower than 100 K. Although the magnetically induced ferroelectricity of CuO is firmly established, no magnetoelectric effect has been observed so far as direct crosstalk between bulk magnetization and electric polarization counterparts. Here we demonstrate that high magnetic fields of E50 T are able to suppress the helical modulation of the spins in the multiferroic phase and dramatically affect the electric polarization. Furthermore, just below the spontaneous transition from commensurate (paraelectric) to incommensurate (ferroelectric) structures at 213 K, even modest magnetic fields induce a transition into the incommensurate structure and then suppress it at higher field. Thus, remarkable hidden magnetoelectric features are uncovered, establishing CuO as prototype multiferroic with abundance of competitive magnetic interactions
High-field phase diagram of a chiral-lattice antiferromagnet Sr(TiO)Cu4(PO4)4
High-field phase diagram of a chiral-lattice antiferromagnet Sr(TiO)Cu4(PO4)4
is studied by means of the ultrasound, dielectric, and magnetocaloric-effect
measurements. These experimental techniques reveal two new phase transitions at
high fields, which have not been resolved by the previous magnetization
experiments. Specifically, the c66 acoustic mode shows drastic changes with
hysteresis with applied fields along the c axis, indicating a strong
magneto-elastic coupling. Combined with the cluster mean-field theory, we
discuss the origins of these phase transitions. By considering the chiral-twist
effect of Cu4O12 cupola units, which is inherent to the chiral crystal
structure, the phase diagram is reasonably reproduced. The agreement between
the experiment and theory suggests that this material is a unique quasi
two-dimensional spin system with competing exchange interactions and chirality,
leading to the rich phase diagram.Comment: 12 pages, 11 figures, 1 tabl
Quadrupolar Susceptibility and Magnetic Phase Diagram of PrNiCd with Non-Kramers Doublet Ground State
In this study, ultrasonic measurements were performed on a single crystal of
cubic PrNiCd, down to a temperature of 0.02 K, to investigate the
crystalline electric field ground state and search for possible phase
transitions at low temperatures. The elastic constant ,
which is related to the -symmetry quadrupolar response, exhibits the
Curie-type softening at temperatures below 30 K, which indicates that the
present system has a non-Kramers doublet ground state. A
leveling-off of the elastic response appears below 0.1 K toward the
lowest temperatures, which implies the presence of level splitting owing to a
long-range order in a finite-volume fraction associated with
-symmetry multipoles. A magnetic field-temperature phase diagram of
the present compound is constructed up to 28 T for [110]. A clear
acoustic de Haas-van Alphen signal and a possible magnetic-field-induced phase
transition at 26 T are also detected by high-magnetic-field
measurements.Comment: 13 pages, 7 figure
Origin of the quasi-quantized Hall effect in ZrTe5
The quantum Hall effect (QHE) is traditionally considered a purely
two-dimensional (2D) phenomenon. Recently, a three-dimensional (3D) version of
the QHE has been reported in the Dirac semimetal ZrTe5. It was proposed to
arise from a magnetic-field-driven Fermi surface instability, transforming the
original 3D electron system into a stack of 2D sheets. Here, we report
thermodynamic, thermoelectric and charge transport measurements on ZrTe5 in the
quantum Hall regime. The measured thermodynamic properties: magnetization and
ultrasound propagation, show no signatures of a Fermi surface instability,
consistent with in-field single crystal X-ray diffraction. Instead, a direct
comparison of the experimental data with linear response calculations based on
an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the
observed Hall response is an intrinsic property of the 3D electronic structure.
Our findings render the Hall effect in ZrTe5 a truly 3D counterpart of the QHE
in 2D systems