Electronic Specific Heat Coefficient Research Articles

Magnetic properties, phase diagram and low-temperature specific heat of Ni50Mn50-xSbx alloys

This study examines the magnetic properties and temperature-composition phase diagram of the Ni50Mn50-xSbx alloys. The addition of Sb into the antiferromagnetic Ni50Mn50 alloy introduces ferromagnetic interaction, resulting in a sudden decrease in the Néel temperature. The characteristic regions of ferromagnetic (FM) and antiferromagnetic (AFM) interactions were determined on temperature-composition phase diagram, as well as compositional dependence of Néel temperature was computed. Increase of Sb content gives rise to an interplay between AFM and FM interactions, leading to the emergence of a spin glass-like state. We identified six distinct magnetic phases in the Ni50Mn50-xSbx system, encompassing AFM, paramagnetic, and FM martensite, as well as spin glass, and paramagnetic and FM austenite. Importantly, this behavior may extend to other Ni50Mn50-xZx (Z = In, Sn) alloys, where addition of Z elements leads to the introduction of FM interaction. Moreover, a significant impact of magnetic ordering on low-temperature specific heat is demonstrated. Neglecting the magnetic contribution in ferromagnetic phase leads to the overestimation of electronic specific heat coefficient by factor of 2.

Magnetism, heat capacity, magnetocaloric effect, and magneto-transport properties of heavy fermion antiferromagnet CeGaSi

We synthesize high-quality single crystal of CeGaSi by a Ga self-flux method and investigate its physical properties through magnetic susceptibility, specific heat and electrical resistivity measurements as well as high pressure effect. Magnetic measurements reveal that an antiferromagnetic order develops below T m ∼ 10.4 K with magnetic moments orientated in the ab plane. The enhanced electronic specific heat coefficient and the negative logarithmic slope in the resistivity of CeGaSi indicate that the title compound belongs to the family of Kondo system with heavy fermion ground states. The max magnetic entropy change −ΔSMmax (μ 0 H⊥c, μ 0 H = 7 T) around T m is found to reach up to 11.85 J⋅kg−1⋅K−1. Remarkably, both the antiferromagnetic transition temperature and −lnT behavior increase monotonically with pressure applied to 20 kbar (1 bar = 105 Pa), indicating that much higher pressure will be needed to reach its quantum critical point.

Unraveling the effects of phason strain on the thermoelectric properties in Ag-In-Yb icosahedral quasicrystals

This study represents the experimental comparative analysis of the thermoelectric properties in an Ag-In-Yb phason-free icosahedral quasicrystal (iQC) and four phason-strained iQCs. The aim is to understand how phason strain affects these properties. The four phason-strained iQCs are 1/1 and 2/1 approximant crystals (1/1 AC and 2/1 AC), a sample grown by the Bridgman method with a high growth rate (phason QC-1), and a sample obtained by phonon–phason coupling (phason QC-2), the magnitude of phason strain decreasing in this order. Their compositions are similar to that of iQC, and in particular, the compositions of phason QC-1 and 2 are exactly the same as that of iQC, making them suitable for clarifying the correlation between physical properties and the magnitude of phason strain. Systematic changes were observed in the electrical resistivity, Seebeck coefficient, and electronic specific heat coefficient with increasing phason-strain magnitude, which can be interpreted as due to the effect of the phason-strain blunting the pseudogap at the Fermi level in the electronic density of states. In contrast, no appreciable dependence of phonon thermal conductivity on the phason-strain magnitude was observed; very low value and a plateau feature observed consistently for all the samples do not arise directly from the quasiperiodicity or high rotational symmetry but from complex structures with a large unit cell.

Probing the superconducting pairing of the La4Be33Pt16 alloy via muon-spin spectroscopy

We report a study of the superconducting pairing of the noncentrosymmetric La4Be33Pt16 alloy using muon-spin rotation and relaxation (µSR) technique. Below K, La4Be33Pt16 exhibits bulk superconductivity (SC), here characterized by heat-capacity and magnetic-susceptibility measurements. The temperature dependence of the superfluid density , extracted from the transverse-field µSR measurements, reveals a nodeless SC in La4Be33Pt16. The best fit of using an s-wave model yields a magnetic penetration depth nm and a superconducting gap meV at zero Kelvin. The single-gapped superconducting state is further evidenced by the temperature-dependent electronic specific heat and the linear field-dependent electronic specific-heat coefficient . The zero-field µSR spectra collected in the normal- and superconducting states of La4Be33Pt16 are almost identical, confirming the absence of an additional field-related relaxation and, thus, of spontaneous magnetic fields below Tc . The nodeless SC combined with a preserved time-reversal symmetry in the superconducting state proves that the spin-singlet pairing is dominant in La4Be33Pt16. This material represents yet another example of a complex system showing only a conventional behavior, in spite of a noncentrosymmetric structure and a sizeable spin–orbit coupling.

Large positive magnetoresistance and high mobility in topological insulator candidate LaP

We reported herein the single crystal growth and the comprehensive study of basic physical properties including electronic transport, magnetic, specific heat of topological insulator candidate LaP. Single crystal LaP of rock salt type structure was synthesized by Sn flux method. Under low temperature and high magnetic field of T= 2 K and B= 9 T, large positive magnetoresistance (LMR) of 500% was discovered. The Hall effect measurements show that the conduction carriers are dominated by holes among the temperature range from 300 K to 2 K, the carrier concentration n_{h} =4.94times 10^{19} cm−3 and n_{e} =5.02times 10^{16} cm−3 and the mobility of LaP reached as high as mu _{h}=1.57times 10^{4} cm2 V−1 S−1 and mu _{e} = 1.55times 10^{3} cm2 V−1 S−1 obtained at 2 K, which can be explained by multiband model physics like other topological quantum material systems with large MR. LaP shows diamagnetism over a wide temperature range from 2 K to 300 K without any magnetic phase transition by susceptibility measurements. No evidence of phase transitions from 2 K to 300 K was observed in the specific heat measurement. The electronic specific heat coefficient is obtained 0.538 m J mol−1 K−2 for LaP single crystal, which responds to a small electron density state near the Fermi level. Our results would be helpful in renewing interest in studying emergent phenomena arisen from topological semimetals. LaP offers a platform for understanding the interactions between large magnetoresistance, high mobility and topological band structure.

Decreasing the Carrier Concentration of ZrNiSn: An Opposite Way to the Best N-Type Half-Heusler Thermoelectrics.

N-type ZrNiSn-based alloys reach a record thermoelectric figure of merit zT ≈1.2 by increasing the carrier concentration to 4-5 × 1020 cm-3 . In this work, It is reported that a comparable zT can also be realized in trace Ru-doped ZrNiSn-based alloy at even lower temperature by decreasing the carrier concentration. Compared to the previously reported Co doping, the doping of Ru results in a more effective reduction in carrier concentration, and thus higher Seebeck coefficient, lower electronic thermal conductivity, and enhanced thermoelectric performance. The electronic specific heat coefficient of the ZrNi1- x Rux Sn sample remains constant with increasing Ru content, indicating no obvious change in the density of states effective mass. Theoretical calculations show that the doping of Ru has negligible effect on the bottom of conduction band. The lattice thermal conductivity is further reduced by alloying Ti and Hf at the Zr site, and the bipolar diffusion is suppressed by doping of 0.5 at.% Sb. As a result, Ti0.25 Zr0.5 Hf0.25 Ni0.99 Ru0.01 Sn0.995 Sb0.005 reaches not only a zT value of 1.1 at 773 K but also a record average zT value of 0.8 in 300 to 873 K, demonstrating the effectiveness of trace Ru doping on boosting the thermoelectric performance of ZrNiSn-based alloys.

A low-temperature face-centered-cubic polymorph of Cu6GeWSe8 with a semiconductor-like conductivity

Hexagonal Cu6GeWSe8 (H-phase) with an intermediate band gap has been reported lately. In this paper, we show a low-temperature face-centered-cubic modification of Cu6GeWSe8 (C-phase), which crystallizes in the noncentrosymmetric space group F-43m with four formula in the cell of dimension a = 11.1372(2) Å. In the C-phase, double layers organized by MeSe4 (Me = Cu, Ge and W) tetrahedra alternately stack along the <111> direction. A weakly first-order or nearly second-order displacive phase transition from cubic to hexagonal polytypes undergoes initially at ∼ 440 °C upon increasing temperature. Electrical resistivity and Seebeck coefficient reveal a semiconductor-like conduction with holes as the predominant charge carriers. The semiconductivity is also supported by the almost zero electronic specific-heat coefficient γ. The mechanism of thermal conduction was analyzed by abstracting electronic and lattice thermal conductivities through thermal transport measurement and meanwhile the thermoelectric properties were characterized. The differences in band structures and formation energy between the two variants were studied by ab-initio calculations, which indicate that the H-phase is a semiconductor and the C-phase is a semimetal with low density of states, and the hexagonal modification is comparatively stable. The cubic polytype of Cu6GeWSe8 expands the Cu-Ge-W-Se system. A stereo phase diagram making reviews on the rich materials, and multiple crystallographic and electronic states in this system was established, which would be helpful to guide for seeking new materials and to probe the interplay between polymorphism and property in chalcogenide family.

Effects of V concentration on the physical properties of Cr1−x Al x alloy system

Electrical resistivity (ρ), magnetic susceptibility (χ) and thermoelectric power (S) studies reported previously on the (Cr1-x Al x )99V1 alloy system indicate a suppression of antiferromagnetism in the concentration range 0.015 ≤ x ≤ 0.040. The present study incorporates Sommerfeld electronic specific heat coefficient (γ), thermal conductivity (κ), Hall coefficient (R H) and analyses of the previous results in order to have a comprehensive study of the alloy system. γ(x) depicts two peaks close to the same concentrations where dS/dT|T→2K(x) have minima, i.e. at x c1 ≈ 0.015 and x c2 ≈ 0.040. Such peaks and minima, respectively, have been considered as key signatures of quantum criticality (QC) in alloys of Cr. Evidence of band structure modification in the alloy system is shown by a change of slope in the Nordheim-Gorter (N-G) relationship showing a minimum at an extrapolated concentration x = 0.035. The slope is positive for the incommensurate (I) spin-density-wave (SDW) alloys with x < 0.035 and a negative for the commensurate (C) SDW alloys with x > 0.035. A behaviour reminiscent of changes in the band structure is also observed in the Lorenz number, L(x), for the alloy with x = 0. R H(T) results in the range 0 ≤ x ≤ 0.026 have a sharp increase in the charge carrier density, n 2K = [qR H(2k)]−1, at the ISDW to paramagnetic (P) phase transition. The concentrations x = 0.015 and x = 0.040 are therefore considered ISDW to P and P to CSDW quantum critical points, respectively.

Effects of equivalent composition on superconducting properties of high-entropy REOBiS2 (RE = La, Ce, Pr, Nd, Sm, Gd) single crystals

Superconductors are influenced by high-entropy alloys (HEAs); these have been investigated in various functional materials. REOBiS2 (RE = La, Ce, Pr, Nd, Sm, and Gd in different combinations) single crystals with HEAs at the RE-site were successfully grown using the flux method. The obtained crystals were plate-shaped (∼1 mm2) with a well-developed c-plane. Ce was present in both trivalent (Ce3+) and tetravalent (Ce4+) electronic configurations; the concentration of Ce4+ at the RE-site was approximately 10 at% in all single crystals. The single crystals showed superconducting transition temperature with zero resistivity within 1.2–4.2 K. The superconducting transition temperature, superconducting anisotropy, electronic specific heat coefficient, and Debye temperature of the crystals were not correlated with the mixed entropy at the RE-site. Except for the electronic specific heat coefficient, the variation of these parameters as a function of mixed entropy showed different trends for equivalent and non-equivalent RE element compositions. Thus, the configuration of RE elements influences the superconducting properties of REOBiS2 single crystals, alluding to a method of modulating transition temperatures.

Magnetic ground state of YbCo2Zn20 probed by muon spin relaxation

The cubic compound YbCo2Zn20 has huge electronic specific heat coefficient γ=7900 mJ/molK2 and its ground state could be located in the vicinity of the quantum critical point. To investigate magnetic ground state, we have carried out muon spin relaxation measurements and confirmed non-magnetic ground state with fluctuating tiny magnetic moment.

Effect of tunable spin-orbit coupling on the superconducting properties of LaRu3Si2 containing kagome-honeycomb layers

We report a detailed investigation of the superconducting properties of the kagome-honeycomb lattice compound $\mathrm{La}{\mathrm{Ru}}_{3}{\mathrm{Si}}_{2}$ by systematically tuning the spin-orbit coupling (SOC) via doping of heavier elements Rh and Ir at the Ru site. All doped samples (for a doping level of 10 at. %) preserve the pristine hexagonal crystal structure in the space group $P{6}_{3}/mmc$, though a marginal lattice compression was noted for Rh doping. Based on the results of dc magnetization, resistivity, and heat capacity measurements, we derived the normal and superconducting state electronic and thermodynamic properties of the pristine and doped samples. Substitution of Ir/Rh at the Ru site of $\mathrm{La}{\mathrm{Ru}}_{3}{\mathrm{Si}}_{2}$ resulted in a rather slow but linear suppression of superconducting transition temperature (${T}_{\mathrm{c}}$), which may be related to the decrease in the density of states. As manifested by the estimated electron-phonon (el-ph) coupling constant (${\ensuremath{\lambda}}_{\mathrm{el}\text{\ensuremath{-}}\mathrm{ph}}\ensuremath{\sim}0.58\text{--}0.66$) and the normalized specific heat jump at ${T}_{\mathrm{c}}$ ($\mathrm{\ensuremath{\Delta}}C/\ensuremath{\gamma}{T}_{c}\ensuremath{\sim}1.5$), the observed superconductivity in $\mathrm{La}{\mathrm{Ru}}_{3}{\mathrm{Si}}_{2}$ and the doped variants is moderately coupled. We observed a nonmonotonous variation of the upper critical field $[{\ensuremath{\mu}}_{0}{H}_{c2}(0)]$ with respect to the doping concentration, as it is influenced by the effective SOC and the coherence length. Most strikingly, we found an enhancement of the superconducting gap parameter $({\mathrm{\ensuremath{\Delta}}}_{0}/{k}_{\mathrm{B}}{T}_{\mathrm{c}})$ with doping concentration even though ${\ensuremath{\lambda}}_{\mathrm{el}\text{\ensuremath{-}}\mathrm{ph}}$ remains essentially unchanged. Moreover, we also notice a nonzero residual electronic specific heat coefficient (${\ensuremath{\gamma}}_{r}$) in the limit $T$ \ensuremath{\rightarrow}0 for all compositions. Interestingly, the evolution of the ${\ensuremath{\gamma}}_{r}$ with the magnetic field can be well described by a $\sqrt{H}$ dependence, which was attributed to multiband superconductivity.

Structure and Physical Properties of the Layered Titanium-Based Pnictide Oxides (EuF)2Ti2Pn2O (Pn = Sb, Bi).

We report two novel titanium-based pnictide oxide compounds (EuF)2Ti2Pn2O (Pn = Sb, Bi), which are synthesized by replacing Sr2+ in (SrF)2Ti2Pn2O [Liu, R. H. Structure and Physical Properties of the Layered Pnictide-Oxides: (SrF)2Ti2Pn2O (Pn = As, Sb) and (SmO)2Ti2Sb2O. Chem. Mater. 2010, 22, 1503-1508] with Eu2+ using a solid-state reaction. (EuF)2Ti2Sb2O exhibits an obvious anomaly in resistivity and heat capacity at T ∼ 195 K, which may arise from the spin-density wave/charge-density wave instability. Similar features are also observed in BaTi2Pn2O, (SrF)2Ti2Pn2O, and Na2Ti2Pn2O (Pn = As and Sb) [Liu, R. H. Structure and Physical Properties of the Layered Pnictide-Oxides: (SrF)2Ti2Pn2O (Pn = As, Sb) and (SmO)2Ti2Sb2O. Chem. Mater. 2010, 22, 1503-1508, Ozawa, T. C. Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors. Sci. Technol. Adv. Mater. 2008, 9, 033003, Wang, X. F. Structure and physical properties for a new layered pnictide-oxide: BaTi2As2O. J. Phys.: Condens. Matter. 2010, 22, 075702, and Xu, H. C. Electronic structure of the BaTi2As2O parent compound of the titanium-based oxypnictide superconductor. Phys. Rev. B 2014, 89, 155108]. Magnetic susceptibility measurements indicate an antiferromagnetic transition at T ∼ 2.5 K for (EuF)2Ti2Sb2O. In particular, the electronic specific heat coefficients of both (EuF)2Ti2Sb2O and (EuF)2Ti2Bi2O are significantly enhanced compared to those of (SrF)2Ti2Pn2O, Na2Ti2Pn2O, and BaTi2Pn2O,1,5,6 which may be due to a strong electron correlation effect in this system. Thus, (EuF)2Ti2Pn2O (Pn = Sb, Bi) may provide new platforms for studying density wave, magnetic ordering, and electron correlation effects.

Critical behavior of the specific heat in Ti-Si amorphous alloys at the metal-insulator transition

In this paper, we report the measurements of specific heat of an amorphous $Ti_{9.5}Si_{90.5}$ alloy located very close to the critical point of the metal-insulator transition. In the presence of a magnetic field, the specific heat is dominated by the Schottky anomaly caused by magnetic moments associated with the dangling bonds in the matrix of amorphous Si. Subtraction of this contribution exposes the behavior of the electronic specific heat coefficient $\gamma$. The coefficient is temperature-independent above 2 K and is, in order of magnitude, close to the value expected in the absence of electron-electron interactions. In the temperature range 0.4-1.5 K, the coefficient $\gamma$ shows an anomalous downturn, which can be approximated by the dependence $\gamma\left(T\right)=\gamma_0ln{(T/T_0)}$, with $T_0\approx0.2$ K . In a companion paper, we found that the Hall coefficient in Ti-Si alloys is affected by the electron-electron interaction up to much higher temperature of 150 K and also varies critically across the metal-insulator transition. We compare our results with theoretical predictions for three models, which can potentially explain the anomalous behavior of the specific heat: generalized non-linear $\sigma$ model, Coulomb glass, and many-body localization.

Explorations on properties of ε′ phase and new crystalline phase of Fe3Ge alloy under high pressures

We calculated the lattice dynamics, elasticity, electron spin polarizability P(EF), and electron specific heat coefficient γ of the L12-Fe3Ge crystalline alloy under high pressure using first-principles method based on density functional theory. By comparing the lattice dynamics and elasticity of the ferromagnetic and non-magnetic systems, it can be found that the spontaneous magnetization of the system induces the dynamic stability of the system at low pressure (less than 6 GPa). Furthermore, the magnetostriction induced by the spontaneous magnetization enhances the elastic modulus of the system. With the increase of pressure, in the pressure range of 130-290 GPa where the spin magnetic moment of the system decreases sharply, the elastic modulus exhibits an abnormal behavior, which leads to double peaks in Poisson's ratio v and Pugh's ratio B/G, correspondingly, double valleys appear in shear modulus G, Young's modulus E and Debye temperature ΘD, which are associated with dynamic instability in the 130-290 GPa. Finally, for the phonon spectrum at 260 GPa with a significant imaginary frequency, the metastable orthogonal Fmmm structure is obtained using the soft mode phase transition theory. After comparing the enthalpy differences with different structures, it is found that the ferromagnetic Fmmm structure is a metastable phase, which is dynamic stable at 0 GPa and 260 GPa.

Inheritance factor on the physical properties in metallic glasses

Material genetic engineering can significantly accelerate the development of new materials. As an important topic in material science and condensed matter physics, the development of metallic glasses (MGs) with specific properties has largely been the result of trial and error since their discovery in 1960. Yet, property design based on the physical parameters of constituent elements of MGs remains a huge challenge owing to the lack of an understanding of the property inheritance from constitute elements to the resultant alloys. In this work, we report the inherent relationships of the yield strength σ y, Young’s modulus E, and shear Modulus G with the valence electron density. More importantly, we reveal that the electronic density of states (EDOSs) at the Fermi surface (E F) is an inheritance factor for the physical properties of MGs. The physical properties of MGs are inherited from the specific element with the largest coefficient of electronic specific heat (γi ), which dominates the value of the EDOS at E F. This work not only contributes to the understanding of property inheritances but also guides the design of novel MGs with specific properties based on material genetic engineering.

Insulator–metal phase transition in novel Sr2OsTiO6 double perovskite via doping - Computational FP study

The structural, electronic, bonding, magnetic, optical and thermal properties of parent perovskite namely SrTiO3 (STO) and novel double perovskite namely Sr2OsTiO6 (SOTO) compounds are analyzed by using Full Potential (FP) - Linearized Augmented Plane Wave (LAPW) method through WIEN2K code. The optimized lattice parameter, bond length, bond angles, Fermi energy (EF), Density of States (DOS) at Fermi Level (FL), electronic specific heat coefficient are computed for the optimized STO and SOTO compounds. At ambient condition SrTiO3 is behaving as a semiconductor with a band gap 1.966 eV and via doping of SrOsO3 and SrTiO3, the resultant product of double perovskite phase namely Sr2OsTiO6 is shifted from the semiconductor state to a normal conductor state. Electron density plots, band structure plots and DOS are illustrated and compared for both STO and SOTO compounds. Diverse bonding and electronic band characteristics are noted and compared. Our band structure calculation results are reveal that the possibility of Electronic Topological Transition (ETT) in these compounds under the effect of doping. Since there is a predominant variation over the structural, electronic and magnetic properties of double perovskite even though not much variation over their mechanical properties. To illustrate the illumination properties of the compounds under study, the optical properties are also analyzed. Hence this study helps to lead the complete examination of suitable photovoltaic properties of STO and SOTO compounds.

Evidence of fully gapped superconductivity in NbReSi: A combined μSR and NMR study

We report a comprehensive study of the noncentrosymmetric NbReSi superconductor by means of muon-spin rotation and relaxation ($\mu$SR) and nuclear magnetic resonance (NMR) techniques. NbReSi is a bulk superconductor with $T_c = 6.5$ K, characterized by a large upper critical field, which exceeds the Pauli limit. Both the superfluid density $\rho_\mathrm{sc}(T)$ (determined via transverse-field $\mu$SR) and the spin-lattice relaxation rate $T_1^{-1}(T)$ (determined via NMR) suggest a nodeless superconductivity (SC) in NbReSi. We also find signatures of multigap SC, here evidenced by the field-dependent muon-spin relaxation rate and the electronic specific-heat coefficient. The absence of spontaneous magnetic fields below $T_c$, as evinced from zero-field $\mu$SR measurements, indicates a preserved time-reversal symmetry in the superconducting state of NbReSi. Finally, we discuss possible reasons for the unusually large upper critical field of NbReSi, most likely arising from its anisotropic crystal structure.

Band Structure Studies of the R5Rh6Sn18 (R = Sc, Y, Lu) Quasiskutteridite Superconductors.

We report on X-ray photoelectron spectroscopy and ab initio electronic structure investigations of the skutterudite-related RhSn superconductors, where R = Sc, Y, and Lu. These compounds crystallise with a tetragonal structure (space group I) and are characterised by a deficiency of R atoms in their formula unit (RhSn, ). Recently, we documented that the vacancies and atomic local defects (often induced by doping) are a reason for the enhancement in the superconducting transition temperature of these materials, as well as metallic () or semimetallic () behaviours in their normal state. Our band structure calculations show the pseudogap at a binding energy of −0.3 eV for the stoichiometric compounds, which can be easily moved towards the Fermi level by vacancies . As a result, dychotomic nature in electric transport of RhSn (metallic or semimetallic resistivity) depends on , which has not been interpreted before. We have shown that the densities of states are very similar for various RhSn compounds, and they practically do not depend on the metal R, while they are determined by the Rh d-and Sn s- and p-electron states. The band structure calculations for ScRhSn have not been reported yet. We also found that the electronic specific heat coefficients for the stoichiometric samples were always larger with respect to the of the respective samples with vacancies at the R sites, which correlates with the results of ab initio calculations.

Frustrated antiferromagnetism and heavy-fermion-like behavior in PrPdAl

We report on the long-range antiferromagnetic ordering with two successive phase transitions at ${T}_{\mathrm{N}1}=4.0\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, ${T}_{\mathrm{N}2}\phantom{\rule{4pt}{0ex}}\ensuremath{\approx}1.3\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and the heavy-fermion-like behaviors in PrPdAl, a Kondo lattice with kagome-like structure of non-Kramers Pr ions in the hexagonal basal plane. The ground-state antiferromagnetism forms by two-thirds Pr ions with nearly full magnetic moment and one-third with strongly frustrated and reduced moment. The easy magnetization axis points along $c$ whereas the ordered Pr $4f$ moments reside in the basal plane, mirroring the important effect of spin frustrations. The electronic specific-heat coefficient is strongly enhanced to $\ensuremath{\sim}940\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}/\mathrm{mol}\phantom{\rule{4pt}{0ex}}{\mathrm{K}}^{2}$, and the Kadowaki-Woods ratio is factor-of-25 smaller than that of conventional heavy-fermion compounds with Kramers doublet ground state. The effective Gr\"uneisen ratio estimated from thermal expansion reveals large values in the vicinity of the broadened phase transition at ${T}_{\mathrm{N}2}$, manifesting its instability against pressure. Accordingly, PrNiAl, a chemically pressurized analog of the titled compound, was found to reveal only one antiferromagnetic transition at a considerably higher temperature of 6.9 K. These results demonstrate that PrPdAl and related homologues can offer excellent cases for investigating competing ground states in frustrated Kondo lattices formed by non-Kramers magnetic ions.

Low-temperature physical properties of new orthorhombic compounds RE2Au3Sn6 (RE = Ce, La)

We have prepared polycrystalline samples of RE2Au3Sn6 (RE = Ce, La) and investigated their magnetic, transport and thermal properties. We found that Ce2Au3Sn6 shows antiferromagnetic transition at T N = 2.54 K, while La2Au3Sn6 shows no phase transition above 0.4 K. The electronic specific heat coefficient of Ce2Au3Sn6 is γ = 350 mJ Ce-mol K2, which indicates that Ce2Au3Sn6 is a heavy fermion compound. The magnetic entropy of Ce2Au3Sn6 at T N is estimated to be 70% of Rln2, which can be attributed to the shielding of the magnetic moment by the Kondo effect.