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The one-dimensional coordination polymers {[CuII(hfac)2]3(m-BNN)}n·nCH2Cl2 (1·CH2Cl2, P1̄) and {[CuII(hfac)2]3(m-BNN)}n (1′, P2/n), were obtained from CH2Cl2 and CHCl3, respectively. 1·CH2Cl2 is transformed to 1 at 335 K.

The cubic neodymium-based compound ${\mathrm{NdCo}}_{2}{\mathrm{Zn}}_{20}$ exhibits a first-order antiferromagnetic (AFM) transition at ${T}_{\text{N}}=0.53$ K. Strong magnetic fluctuations at temperatures up to 5 K were suggested by the downward curvature of the electrical resistivity $\ensuremath{\rho}(T)$ and the reduced magnetic entropy ${S}_{\text{m}}$ of $0.5R\mathrm{ln}2$ at ${T}_{\text{N}}$. In this study, we measured $\ensuremath{\rho}(T)$, the isothermal magnetization $M(B)$, magnetic susceptibility $\ensuremath{\chi}(T)$, and specific heat $C(T)$ of ${\mathrm{NdCo}}_{2}{\mathrm{Zn}}_{20\ensuremath{-}x}{\mathrm{Cd}}_{x}$ for $x=1$ and ${\mathrm{NdCo}}_{2}{\mathrm{Zn}}_{20\ensuremath{-}y}{\mathrm{Ga}}_{y}$ for $y=1$ and 2. The sharp peak of the magnetic specific heat ${C}_{\text{m}}(T)$ at ${T}_{\text{N}}$ for $x$ = 0 is changed to a weak and broad maximum at 0.55 K for $x$ = 1. This drastic change in ${C}_{\text{m}}(T)$ suggests that the isovalent Cd substitution for Zn disorders the exchange interactions between the Nd moments to hinder the first-order AFM transition. On the other hand, ${C}_{\text{m}}(T)$ for $y=1$ and 2 exhibits a lambda-shaped anomaly, which is a characteristic of a second-order AFM transition, at elevated temperatures of 0.78 and 1.5 K, respectively. The stabilization of the AFM order by the Ga substitution indicates that $4p$ electron doping strengthens the AFM interaction. We therefore propose that the first-order transition in ${\mathrm{NdCo}}_{2}{\mathrm{Zn}}_{20}$ is maintained by competitive magnetic interactions inherent in the Nd diamond sublattice.

The cerium-based compound $\mathrm{Ce}{\mathrm{Pt}}_{6}{\mathrm{Al}}_{3}$, in which Ce atoms form a honeycomb lattice hosting magnetic frustration, has a heavy-fermion ground state. We have observed development of magnetic order in partially Pd-substituted $\mathrm{Ce}{({\mathrm{Pt}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x})}_{6}{\mathrm{Al}}_{3}$ series up to $x$ = 0.3 by the measurements of magnetic susceptibility, electrical resistivity \ensuremath{\rho}, and specific heat $C$. In the whole range of $x$, the unit cell volume remains unchanged within 0.2%, and the effective magnetic moment stays at $2.4\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}/\mathrm{Ce}$. For $x$ = 0.05, both $C/T$ and $\ensuremath{\rho}(T)$ jump on cooling at ${T}_{m}=1.8\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. With increasing $x$ to 0.2, ${T}_{m}$ increases to 3.8 K, where $C/T$ shows a pronounced \ensuremath{\lambda}-type anomaly. Application of magnetic fields suppresses ${T}_{m}$, which is indicative of an antiferromagnetic (AFM) ordered state. Thus, a long-range AFM order is induced by the substitution of isovalent Pd for Pt in $\mathrm{Ce}{\mathrm{Pt}}_{6}{\mathrm{Al}}_{3}$ without carrier doping and chemical pressure. We attribute the emergence of AFM order in $\mathrm{Ce}{({\mathrm{Pt}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x})}_{6}{\mathrm{Al}}_{3}$ to the randomness in the spin-orbit interaction in the Pt-Pd sublattice, which weakens both the coherent Kondo effect and magnetic frustration in the honeycomb Kondo lattice.

Kondo semiconductors based on rare-earth elements possess a narrow gap in the renormalised density of states near the Fermi level. Their ground states remain nonmagnetic due to strong hybri...

We have synthesized magnesium cage compounds $R$Ni$_{2}$Mg$_{20}$ ($R$ = Pr and Nd). We report the measurements of electrical resistivity $\rho$, magnetic susceptibility $\chi$, isothermal magnetization $M$, and specific heat $C$. Polycrystalline samples with $R$ = Pr and Nd were obtained by annealing, while the counterparts for $R$ = La, Ce, and Y were found to be absent. The ${\rho}(T)$ data for $R$ = Pr and Nd monotonically decrease on cooling from 300 K to 40 K and exhibit shoulders at around 13 K and 15 K, respectively. The Curie-Weiss behaviors of the ${\chi}(T)$ data indicate the trivalent states of both the Pr and Nd ions. For $R$ = Pr, the maximum in $C(T)$ at around 7 K is reproduced by a doublet-triplet two-level model with an energy gap of 14 K. The peak in $C(T)$ at 0.7 K is attributed to a short-range order of quadrupolar degrees of freedom in the non-Kramers ground doublet. On the other hand, for $R$ = Nd, a maximum in $C(T)$ at around 9 K is explained by thermal excitation from a ground state doublet to an excited quartet separated by 23 K. Upon further cooling, $C(T)$ shows a lambda-shaped peak at 1.5 K. By applying magnetic fields up to 2 T, the peak becomes broad and shifts to higher temperatures, which is a characteristic of a ferromagnetic order., Comment: 7 pages, 10 figures

Superconductivity in ${\mathrm{PrIr}}_{2}{\mathrm{Zn}}_{20}$ appears at ${T}_{\mathrm{c}}=0.05$ K in the presence of an antiferroquadrupolar order below ${T}_{\mathrm{Q}}=0.11$ K. We have studied pressure dependences of ${T}_{\mathrm{c}}$, ${T}_{\mathrm{Q}}$, and non-Fermi-liquid behaviors in the resistivity $\ensuremath{\rho}(T)$ by using two pressure-transmitting media: argon, maintaining highly hydrostatic pressure, and glycerol, which solidifies above 5 GPa, producing nonhydrostatic pressure. Upon applying $P$ with argon up to 10.6 GPa, ${T}_{\mathrm{c}}$ hardly changes, while ${T}_{\mathrm{Q}}$ monotonically increases from 0.11 to 0.23 K. With glycerol, however, ${T}_{\mathrm{Q}}$ and ${T}_{\mathrm{c}}$ simultaneously fall below 0.04 K at 6.3 GPa. The contrasting results indicate that on-site quadrupolar fluctuations induce superconductivity in this compound.

We have studied the pressure effect on the rattling of tetrahedrite ${\mathrm{Cu}}_{10}{\mathrm{Zn}}_{2}{\mathrm{Sb}}_{4}{\mathrm{S}}_{13}$ (CZSS) and type-I clathrate ${\mathrm{Ba}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Sn}}_{30}$ (BGS) by specific heat and x-ray diffraction measurements. By applying pressure $P$, the rattling energy for CZSS initially decreases and steeply increases for $Pg1\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. By contrast, the energy for BGS increases monotonically with $P$ up to 6.5 GPa. An analysis of the pressure-dependent specific heat and x-ray diffraction indicates that the out-of-plane rattling of the Cu atoms in the ${\mathrm{S}}_{3}$ triangle of CZSS originates from the chemical pressure, unlike the rattling of the Ba ions among off-center sites in an oversized cage of BGS. The rattling in CZSS ceases upon further increasing $P$ above 2 GPa, suggesting that Cu atoms escape away from the ${\mathrm{S}}_{3}$ triangle plane.

The cubic Kondo lattice ${\mathrm{YbCo}}_{2}{\mathrm{Zn}}_{20}$ is one of the heaviest known Fermi liquids. We have measured the low-temperature electrical resistivity $\ensuremath{\rho}(T)$, magnetic susceptibility $\ensuremath{\chi}(T)$, and heat capacity $C(T)$ in single crystals of $\mathrm{Yb}{({\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x})}_{2}{\mathrm{Zn}}_{20}$ ($x\ensuremath{\le}0.126$) and $\mathrm{Yb}{({\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{y})}_{2}{\mathrm{Zn}}_{20}$ ($y\ensuremath{\le}0.07$). While pure ${\mathrm{YbCo}}_{2}{\mathrm{Zn}}_{20}$ displays maxima in $\ensuremath{\rho}(T)$ and $\ensuremath{\chi}(T)$, ascribed to an enhanced crystal electric field (CEF) degeneracy, the maxima are suppressed by small amounts ($\ensuremath{\approx}6$ at.%) of substitutions of the Co atoms. This goes along with a suppression of superheavy Fermi liquid behavior as manifested in the divergence of $C/T$. We ascribe the observations to local distortions at the Yb site due to the chemical disorder in the environment, rather than to a chemical pressure effect. This fragileness to the local distortion indicates that superheavy Fermion behavior in ${\mathrm{YbCo}}_{2}{\mathrm{Zn}}_{20}$ is closely linked to an enhanced CEF degeneracy.

Superconductivity in PrIr$_{2}$Zn$_{20}$ appears at $T_{\rm c} = 0.05$ K in the presence of an antiferroquadrupolar order below $T_{\rm Q} = 0.11$ K. We have studied pressure dependences of $T_{\rm c}$, $T_{\rm Q}$, and non-Fermi liquid behaviors in the resistivity $\rho (T)$ by using two pressure transmitting media: argon maintaining highly hydrostatic pressure, and glycerol, which solidifies above 5 GPa producing nonhydrostatic pressure. Upon applying $P$ with argon up to 10.6 GPa, $T_{\rm c}$ hardly changes, while $T_{\rm Q}$ monotonically increases from 0.11 to 0.23 K. With glycerol, however, $T_{\rm Q}$ and $T_{\rm c}$ simultaneously fall below 0.04 K at 6.3 GPa. The contrasting results indicate that onsite quadrupolar fluctuations induce superconductivity in this compound., Comment: 15 pages, 4 figures

We synthesized a new ternary stannide CePd 3 Sn 2 and determined its crystal structure from single crystal x-ray diffraction. This compound crystallizes in the orthorhombic structure with space group Pnma (No.62). One-dimensional chains of the shortest Ce-Ce contacts at 0.47663(1) nm run along the b axis. Both specific heat C and susceptibility χ of polycrystalline samples show a pronounced peak at T N = 0.6 K indicating an antiferromagnetic order. An obvious tail in C ( T ) appears in the temperature range from T N up to 3 K where the magnetic entropy S m reaches Rln2. Meanwhile, the electrical resistivity ρ exhibits an upward curvature without showing any sign of Kondo scattering. The unusual behaviors of C ( T ) and ρ ( T ) above T N are attributed to antiferromagnetic short-range correlations in the Ce-Ce chain.

PrIr2Zn20 exhibits an antiferroquadrupolar (AFQ) order at TQ = 0.11 K, above which temperature the electrical resistivity ρ(T) shows an upward curvature and the magnetic specific heat divided by temperature Cm/T follows − lnT dependence. The non-Fermi Liquid (NFL) behaviors have suggested formation of a quadrupole Kondo lattice. In the present work, we have studied the effect of Ga substitution for Zn on the NFL behavior by the measurements of the specific heat C, the magnetic susceptibility χ, and ρ of PrIr2Zn20-xGax (0 ≤ x ≤ 0.25). With increasing x, the characteristic temperature T0 defined as the temperature where the magnetic entropy Sm reaches (3/4)Rln2 is increased by a factor of 3.5. Similarly, another characteristic temperature TR below which ρ(T) starts decreasing with the upward curvature increases with x by a factor of 1.2. The increments of both T0 and TR may be attributed to the possible split of the Γ3 doublet by symmetry lowering of the Pr sites. Otherwise, the quadrupole Kondo lattice would be stabilized by the enhanced c-f hybridization due to the increment of the 4p electronic density and/or the chemical pressure effect.

Electrical resistivity ρ , magnetization M and specific heat C are reported for polycrystalline samples of the hexagonal system PrRh 3 . The magnetic susceptibility M / B obeys the Curie-Weiss law with the effective magnetic moment μ eff = 3.88 μ B /Pr and the paramagnetic Curie temperature θ p = +2.9 K, which indicates ferro-type magnetic interaction between the trivalent Pr ions. A cusp in C ( T ) at 3.0 K coincides with a bend in ρ ( T ). Applying magnetic fields, the peak broadens and shifts to higher temperatures. The field dependence indicates a ferro-type magnetic order. The magnetic entropy S m is (1/3) R ln2 at T C = 3.0 K, suggesting that part of the Pr ions take part in the magnetic order. A broad tail of the magnetic specific heat C m observed above T C may result from short-range correlations and/or fluctuations of the active magnetic dipole and quadrupoles in the ground state doublet.

The rare-earth chiral compound ${\mathrm{DyNi}}_{3}{\mathrm{Ga}}_{9}$ with trigonal structure shows successive phase transitions at 10, 9, 5.5, and 2.5 K. We previously reported that the transverse elastic modulus ${C}_{66}$ exhibits significant softening toward ${T}_{\mathrm{Q}}=10$ K and the phase transition at ${T}_{\mathrm{Q}}$ is ferroquadrupolar ordering due to the quasidegenerate quartet under a crystal electric field (CEF). To investigate the order parameter and magnetic field-temperature phase diagrams of the ferroquadrupolar ordering, we performed ultrasonic measurements under magnetic fields. ${T}_{\mathrm{Q}}$ decreases drastically at low fields in the magnetic field in the $c$ plane. In contrast, ${T}_{\mathrm{Q}}$ remains even at high fields in the field along the $c$ axis. We found anisotropic and complex phase diagrams, and this anisotropy of the diagrams originates from the field dependences of the CEF energies and a quadrupole interaction. From our calculated results, we propose that the order parameter of the ferroquadrupolar ordering will be the electric quadrupole ${O}_{xy}$. There are first-order successive phase transitions in the field sweep in the $c$ plane, and a magnetic-field-induced phase appears in the phase diagram for the $a$ axis.

The crystalline electric field (CEF) level scheme and magnetic structure of a tetragonal antiferromagnet CePd

Structural, transport and magnetic properties of single-crystalline samples of a praseodymium-based cubic compound PrMgNi4 were studied. The single-crystal X-ray structural analysis revealed that Mg atoms are substituted for the Pr atoms at the 4a site by 4.5%. The chi(T) data follow the Curie-Weiss law with an effective moment for the Pr3+ ion. The magnetic specific heat divided by temperature, Cm/T, shows a broad maximum at around 3 K, which is reproduced by a two-level model with a ground state doublet. On cooling below 1 K, Cm/T approaches a constant value, which behavior is reproduced by a random two-level model. The twofold degeneracy of the ground state is lifted by symmetry lowering due to the substituted Mg atoms for the Pr atoms or strong hybridizations between the 4f2 electron states and conduction bands, which hinders the long-range quadrupole order.

We have synthesized single crystals of CePt6Al3 in which Ce atoms form a honeycomb lattice in a trigonal basal plane. The measurements of magnetic susceptibility χ, electrical resistivity ρ, thermo...

Magnetic properties of an Yb-based semiconductor YbCuS2 with a zigzag chain of Yb3+ ions were studied. The Curie–Weiss behavior of the magnetic susceptibility χ(T) indicates antiferromagnetic inter...

The Ce atoms in CeIrSn form a quasikagome lattice in the hexagonal $c$ plane. Our single-crystal x-ray diffraction analysis has confirmed the absence of superstructure in the ZrNiAl-type structure. Motivated by the recent observation of quantum critical behaviors in the isostructural and isoelectronic compound CeRhSn, we have studied low-temperature properties of single-crystalline samples of CeIrSn by measuring the electrical resistivity, magnetic susceptibility $\ensuremath{\chi}$, magnetization $M$, and specific heat $C$ down to 0.05 K. Our study does not show evidence of a long-range magnetic ordering down to the lowest temperature. The $\ensuremath{\chi}(T)$ data show an Ising character, ${\ensuremath{\chi}}_{c}\ensuremath{\gg}{\ensuremath{\chi}}_{a}$, and power-law behaviors at low temperatures: ${\ensuremath{\chi}}_{c}\ensuremath{\propto}{T}^{\ensuremath{-}0.8}$ and ${\ensuremath{\chi}}_{a}\ensuremath{\propto}{T}^{\ensuremath{-}0.6}$. When external field $B$ is applied along the $a$ axis, both $M(B)$ and $C(B)/T$ exhibit metamagnetic anomalies at 5.5 T, which resemble those observed in CeRhSn at 3.5 T. We attribute the metamagnetic crossover under in-plane magnetic fields to the alleviation of magnetic frustration inherent in the quasikagome Ising Kondo lattice.

Electrical resistivity ρ(T) and specific heat C(T) measurements have been made on the diluted 4f^{2} system Y(Pr)Ir_{2}Zn_{20}. Both data of ρ and magnetic specific heat C_{m} per Pr ion are well scaled as a function of T/T_{0}, where T_{0} is a characteristic temperature of non-Fermi-liquid (NFL) behaviors. Furthermore, the temperature dependences of ρ and C_{m}/T agree with the NFL behaviors predicted by the two-channel Kondo model for the strong coupling limit. Therefore, we infer that the observed NFL behaviors result from the single-site quadrupole Kondo effect due to the hybridization of the 4f^{2} states with multichannel conduction electrons.

The chiral compound ${\mathrm{YbNi}}_{3}{\mathrm{Ga}}_{9}$ with a trigonal structure, which is a valence fluctuating material at ambient pressure, undergoes a magnetic order under pressure above ${P}_{\mathrm{c}}$ of 9 GPa. We have studied the temperature-pressure-magnetic-field phase diagrams of this compound by ac calorimetric measurements under pressures $P$ up to 12 GPa. The specific heat $C$ divided by temperature $T,C/T$, markedly increases with applying pressure up to ${P}_{\mathrm{c}}$. At 8.6 GPa, just below ${P}_{\mathrm{c}},C/T$ exhibits $\ensuremath{-}ln\phantom{\rule{0.16em}{0ex}}T$ dependence in the temperature range 2--9 K. At $Tl1.5\phantom{\rule{0.16em}{0ex}}\mathrm{K},C/T$ is saturated to a large value $1\phantom{\rule{0.16em}{0ex}}\mathrm{J}/{\mathrm{K}}^{2}\phantom{\rule{0.16em}{0ex}}\mathrm{mol}$, i.e., heavy Fermi-liquid behavior. At $P=9.3\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, just above ${P}_{\mathrm{c}}$, a broad maximum in $C/T$ appears at 1.6 K, indicating the onset of the magnetic order. With increasing $P$ further, the maximum shifts to a higher temperature and transforms to a sharp $\ensuremath{\lambda}$-type peak at 5 K for $P\ensuremath{\ge}11\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. By using the temperature, pressure, and magnetic field $B$ dependences of the specific-heat data $C(T,P,B)$ obtained under $B\ensuremath{\perp}c$ and $B\ensuremath{\parallel}c$, we have constructed $B\text{\ensuremath{-}}T$ phase diagrams at each $P$ value. Another field-induced ordered phase appears in the diagrams only for $B\ensuremath{\perp}c$ at $P\ensuremath{\ge}11\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. The origin of this induced phase is discussed in relation to the chiral soliton lattice and the skyrmion lattice reported for chiral magnets.

We have measured the strain, magnetization, and specific heat of the antiferromagnetic (AFM) Kondo semiconductors $\mathrm{Ce}{T}_{2}\mathrm{A}{\mathrm{l}}_{10}$ ($T=\mathrm{Ru}$ and Os) under uniaxial pressures applied along the orthorhombic axes. We found a linear dependence of ${T}_{\mathrm{N}}$ on the $b$-axis parameter for both compounds under uniaxial pressure $P\ensuremath{\parallel}b$ and hydrostatic pressure. This relation indicates that the distance between the Ce-$T$ layers along the $b$ axis is the key structural parameter determining ${T}_{\mathrm{N}}$. Furthermore, the pressure dependence of the spin-flop transition field indicates that Ce-Ce interchain interactions stabilize the AFM state with the ordered moments pointing to the $c$ axis.

lectronic structure of the Kondo lattices YbNiX3 (X =Si, Ge) has been investigated by means of hard x-ray photoemission spectroscopy (HAXPES) with hν = 5.95 keV. From the Yb 3d HAXPES spectra, the Yb valence in YbNiSi3 is estimated to be ∼ 2.92, which is almost temperature-independent. On the other hand, the valence in YbNiGe3 is estimated to be 2.48 at 300 K, showing significant valence fluctuation, and gradually decreases to 2.41 at 20 K on cooling. The Ni 2p3/2 and Yb3+ 4f peaks exhibit opposite energy shifts amounting to ∼ 0.6 eV between YbNiSi3 and YbNiGe3. We propose a simple model for the electronic structure of YbNiX3 based on the HAXPES results. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Magnetic properties in a caged compound NdOs2Zn20 have been studied by the measurements of magnetization M, magnetic susceptibility M/B, and specific heat C. The measurements indicate that NdOs2Zn20 shows a structural transition at Ts = 62K and a ferromagnetic transition at TC = 0.6K. The structural transition is also observed in the La counter-part LaOs2Zn20 at Ts = 151K. The results of M (T)/B, M (B), and C(T) of NdOs2Zn20 are reproduced by a crystalline electrical field scheme with a Kramers doublet ground state.

CeRhSn with a quasikagome lattice of Ce atoms in the hexagonal $c$ plane has been expected to be in close vicinity to a zero-field quantum criticality derived from magnetic frustration. We have studied how the ground state changes with substitution of Pd for Rh in $\mathrm{CeR}{\mathrm{h}}_{1\ensuremath{-}x}\mathrm{P}{\mathrm{d}}_{x}\mathrm{Sn}$ $(x\ensuremath{\le}0.75)$ by measuring the specific heat $C$, magnetic susceptibilities ${\ensuremath{\chi}}_{\mathrm{dc}}$ and ${\ensuremath{\chi}}_{\mathrm{ac}}$, magnetization $M$, electrical resistivity \ensuremath{\rho}, and magnetoresistance. For $x=0$, the field dependence of ${\ensuremath{\chi}}_{\mathrm{ac}}$ at $T=0.03\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ shows a peak at $B\ensuremath{\parallel}a=3.5\phantom{\rule{0.16em}{0ex}}\mathrm{T}$, confirming the spin-flop crossover in the field applied along the hard axis. The temperature dependence of ${\ensuremath{\chi}}_{\mathrm{ac}}$ shows a broad maximum at 0.1 K whereas $C/T$ continues to increase down to 0.08 K. For $x\ensuremath{\geqq}0.1,\ensuremath{\rho}(T)$ is dominated by incoherent Kondo scattering and both $C/T$ and ${\ensuremath{\chi}}_{\mathrm{ac}}(T)$ exhibit peaks, indicating the development of an antiferromagnetic order. The ordering temperature rises to 2.5 K as $x$ is increased to 0.75. Our results indicate that the ground state in the quasikagome Kondo lattice $\mathrm{CeR}{\mathrm{h}}_{1\ensuremath{-}x}\mathrm{P}{\mathrm{d}}_{x}\mathrm{Sn}$ leaves the quantum critical point at $x=0$ with increasing $x$ as a consequence of suppression of both the magnetic frustration and Kondo effect.

The praseodymium-encaged compound PrIr2Zn20 with a non-Kramers doublet ground state undergoes an antiferroquadrupolar transition at TQ = 0.11 K. On heating above TQ, the magnetic specific heat Cm/T...

Electrical resistivity ρ, magnetization M, and specific heat C were measured for 4f3 Kramers systems NdT2Zn20 (T = Co and Rh), in which Nd3+ ions form a diamond sublattice. The magnetic susceptibil...

The crystalline electric field (CEF) level scheme and magnetic structure of a tetragonal antiferromagnet CePd5Al2 with [Formula: see text] K and [Formula: see text] K were studied by neutron scattering, magnetization and magnetoresistance measurements. Inelastic neutron scattering measurements on the powder sample revealed CEF excitations at 21.3 and 22.4 meV. The derived wave functions of the CEF ground state for the Ce3+ ion consist primarily of [Formula: see text] under the tetragonal symmetry. By means of single-crystal neutron diffraction, magnetic Bragg peaks characterized by a propagation vector [Formula: see text] were observed at [Formula: see text]. Our analysis indicates a sinusoidally modulated magnetic structure with amplitude of 2.0(1) [Formula: see text]/Ce, where the magnetic moments point to the [Formula: see text]-axis. The intensity of the third-order harmonic at 0.8 K is 1/30 as small as that expected for an antiphase structure, suggesting that the modulated structure remains at least down to 0.8 K. Both the magnetization and magnetoresistance show several anomalies in the magnetically ordered phase, indicating field-induced successive changes of the magnetic structure.

A developed alternating current calorimeter for measuring the absolute value of specific heat C of a very small sample under a pressure up to 10 GPa and low temperature below 10 K is described. A Bridgman anvil cell made of tungsten carbide with a top diameter of 3 mm is used. A hollow at the top prevents expansion of the sample space over the anvil top. Two chip resistors, which act as a thermometer and a heater, are mounted on the outer part of a copper–beryllium gasket with a frying pan-like shape. Thus, the thermometer is not pressurized. In order to isolate the gasket from the anvil thermally, diamond powder with a grain size of 0.25 μm is placed on the anvil top. Two jumps of C at the superconducting transitions of Pb (3.3 mg) and In (5.0 mg) are observed under various pressures up to 9 GPa, as clearly as those at the ambient pressure.

Orbital degrees of freedom in condensed matters could play important roles in forming a variety of exotic electronic states by interacting with conduction electrons. In 4f electron systems, because of strong intra-atomic spin-orbit coupling, an orbitally degenerate state inherently carries quadrupolar degrees of freedom. The present work has focussed on a purely quadrupole-active system PrIr2Zn20 showing superconductivity in the presence of an antiferroquadrupole order at TQ = 0.11 K. We observed non-Fermi liquid (NFL) behaviors emerging in the electrical resistivity and the 4f contribution to the specific heat, C_4f, in the paramagnetic state at T > TQ. Moreover, in magnetic fields below 6 T, all data set of the electrical resistivity and C_4f(T) are well scaled with characteristic temperatures T0's. This is the first observation of the NFL state in the nonmagnetic quadrupole-active system, whose origin is intrinsically different from that observed in the vicinity of the conventional quantum critical point. It implies possible formation of a quadrupole Kondo lattice resulting from hybridization between the quadrupoles and the conduction electrons. Below 0.13 K, the electrical resistivity and C_4f(T) exhibit anomalies as B approaches 5 T. This is the manifestation of a field-induced crossover toward a Fermi-liquid ground state in the quadrupole Kondo lattice., 8 pages, 6 figures

We report magnetic, transport, and specific-heat measurements for single crystals of the antiferromagnetic (AFM) Kondo semiconductor alloy series Ce(Ru1−xOsx)2Al10 (0 ≤ x ≤ 1), which crystallize in...

We report on thermoelectric and Raman scattering studies of single crystalline samples of a type I clathrate Ba8Ga16Sn30. The n- and p-type samples have a thermopower of −300 μV/K and +270 μV/K, and electrical resistivity of 20 mΩ cm and 40 mΩ cm at room temperature, respectively. Regardless of the charge carrier type, the lattice thermal conductivity κ L shows typical glass-like behavior. The low-energy vibration of Ba(2) in the tetrakaidecahedron is manifested in the Raman scattering spectrum as a peak at 15 cm−1. This energy agrees with the characteristic vibrational temperature of 20 K derived from the analysis of the specific heat data with a soft-potential model. The fact that both the vibrational energy and the magnitude of κ L for Ba8Ga16Sn30 are lowest among the type I clathrates is evidence that off-center vibrations are responsible for the strong reduction of κ L. Analysis of κ L(T) revealed that the positional disorder associated with the off-center vibrations acts as the Rayleigh scattering center, and the coupling between guest vibrational modes and acoustic phonons is stronger than that in Sr8Ga16Ge30 and Eu8Ga16Ge30.

We report a detailed study of the pressure–temperature ( P – T ) phase diagrams of two Yb-based heavy-fermion compounds, namely, the antiferromagnet YbAgGe and weak ferromagnet YbRhSb. YbAgGe with a quasikagome lattice of Yb ions undergoes two magnetic phase transitions at T M1 = 0.8 K (second order) and T M2 =0.65 K (first order). With increasing pressure ( P ) up to 0.5 GPa, the transitions at T M1 and T M2 merge into one transition. For 0.5 < P < 1.6 GPa, T M2 remains constant and abruptly rises above 1.6 GPa. This rise occurs with a significant change in the specific heat anomaly from a small cusp at T M2 into a large peak at T M3 . This finding suggests that the suppressed magnetic entropy is released due to geometrical frustration at ambient pressure. On the other hand, YbRhSb undergoes a transition into an unusual magnetic state at T M1 = 2.7 K, which is associated with a small spontaneous moment of 3 ×10 -3 µ B /Yb. Measurements of the resistivity, specific heat, and ac magnetic susceptibility χ a...

We have investigated the anomalous ordered phase of CeTe under high pressure, which has been suggested to be an antiferroquadrupole ordered phase. An anisotropic magnetic phase diagram has been obtained from magnetization and specific heat measurements for the three main field directions along [100], [110], and [111]. We discuss the magnetic phase diagram using a two-sublattice mean-field calculation including antiferromagnetic and antiferroquadrupolar interactions. The anomalous ordered phase can be interpreted as an antiferromagnetic ordered phase, which is strongly affected by the antiferroquadrupolar interaction through the off-diagonal matrix element between the Γ7 crystal-field ground state and the Γ8 excited state., This work was supported by Grants-in-Aid for Scientific Research (Nos. 21204456, 21102515, and 2430087) from JSPS and MEXT.

Magnetic and thermoelectric properties of the skutterudites AT4Sb12 filled with non-magnetic atoms, A=Ca, Sr, Ba and La, are found to depend strongly on the transition-metal elements, T=Fe, Ru and Os. The strong spin fluctuations in the Fe-based compounds manifest themselves as an enhanced specific-heat coefficient γ=100 mJ/K2 mol. The maximum of the magnetic susceptibility at 50 K observed for A=Ca, Sr and Ba is a characteristic of a nearly ferromagnetic system. The increase of the paramagnetic Curie temperature from 3 to 54 K on going from A=La, Ba, Sr to Ca indicates the enhancement of ferromagnetic interactions in the Fe 3d narrow band. Except for A=La, a marked shoulder appears in the thermopower at 50 K which is totally suppressed by the application of a magnetic field of 14 T. The Ru compounds are metallic diamagnets with γ=10 mJ/K2 mol, while the Os compounds are strongly enhanced Pauli paramagnets with γ=45 mJ/K2 mol and show behaviors of a strongly coupled electron–phonon system. The lattice thermal conductivity for either A=La or T=Os does not show a peak near 50 K and its value is much smaller than other compounds. The strong phonon scattering can be caused by rattling of the relatively small La3+ ion in the T4Sb12 cage or tunneling of Sr2+ and Ba2+ ions in the Os4Sb12 cage.

We investigated ground state properties of a heavy-fermion antiferromagnet Ce 7 Ni 3 under hydrostatic pressures and magnetic fields. This compound undergoes two antiferromagnetic phase transitions at T N1 = 1.9 K and T N2 = 0.7 K. Below T N1 , a spin-density-wave (SDW) develops. Upon applying rather weak pressure 0.39 GPa = P c , both T N1 and T N2 vanish, and non-Fermi liquid behavior appears in the specific heat and magnetic susceptibility. The enhancement of residual resistivity along the a axis near P c is attributed to the increased spin fluctuations along the a axis. By applying fields B along the c axis, T N1 is suppressed and vanishes at 0.3 T. Magnetoresistance, specific-heat, and magnetization measurements revealed another field-induced magnetic (FIM) phase in the region B || c > 0.7 T and T < 0.5 K. Neutron diffraction experiments indicate that the magnetic unit cell in the c-plane for the FIM phase is treble that of the chemical unit cell. Moreover, this magnetic reflection intensity remains even in the region between the FIM phase and SDW phase. This observation indicates the presence of large spin fluctuations in the c-plane associated with the magnetic frustration, which should be responsible for the magnetic instability of Ce 7 Ni 3 .