We have synthesized magnesium cage compounds $R$Ni$_{2}$Mg$_{20}$ ($R$ = Pr and Nd). We report the measurements of electrical resistivity $ρ$, magnetic susceptibility $χ$, 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 $ρ(T)$ 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 $χ(T)$ 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.
The role of controlled disorder in the strong correlated narrow gap semiconductor candidate FeGa$_3$ has been investigated. Polycrystalline samples were synthesized by the combination of arc-melting furnace and successive annealing processes. Deviations of the occupation number of Fe and Ga sites from those expected in the pristine compound were quantified with X-ray analysis. Besides that, electrical transport and magnetization measurements reveal that hierarchy in Fe and Ga site disorder tunes the ground state of FeGa$_3$ from paramagnetic semiconducting to a magnetic metal. These findings a…
The strongly correlated system Ho11B12 with boron sublattice Jahn-Teller instability and nanoscale electronic phase separation (dynamic charge stripes) was studied in detail by inelastic neutron scattering (INS), magnetometry and heat capacity measurements at temperatures in the range 3-300 K. From the analysis of registered INS spectra, we determined parameters of the cubic crystal field at holmium sites, B4=- 0.333 meV and B6= -2.003 meV (in Stevens notations), with an unconventional large ratio B6/B4 pointing on the dominant role of conduction electrons in the formation of a crystal field p…
Double-phase transition and giant positive magnetoresistance in the quasi-skutterudite Gd$_3$Ir$_4$Sn$_{13}$
重新研究了笼状结构准方钴矿Gd $_3$ Ir $_4$ Sn $_{13}$的磁性、热力学和电/热输运性质。磁化强度$M(T)$、比热$C_p(T)$和电阻率$ρ(T)$表明在$T_{N1}\sim$ 10 K和$T_{N2}\sim$ 8.8 K处存在双相变，这在以前的报道中没有观察到。在热输运数据中也可以看到反铁磁转变，从而表明Sn基准方钴矿中电子和晶格自由度之间存在密切联系。$ρ(T)$的温度依赖性进行了分析的费米液体图片相关的电阻率的幂律。在9 T磁场下，在2K下观察到Gd $_3$ Ir $_4$ Sn $_{13}$的巨正磁电阻（MR）$\approx$ 80 $\%$.巨磁电阻和双磁转变可归因于Gd $_3$ Ir $_4$ Sn $_{13}$的准笼状和层状反铁磁结构易受结构畸变和/或偶极或自旋重取向效应的影响。在这类3：4：13型合金中观察到的巨大的MR值，特别是在Gd化合物中，是这项工作的亮点。
Praseodymium-based 1-2-20 cage compounds Pr$T_2X_{20}$ ($T$ is generally Ti, V, Nb, Ru, Rh, Ir; and $X$ is either Al, Zn or Cd) provide yet another platform to study non-trivial electronic states of matter ranging from topological and magnetic orders to unconventional multipolar orders and superconductivity. In this paper, we report measurements of the electronic heat capacity in two Pr-based 1-2-20 materials: PrNi$_2$Cd$_{20}$ and PrPd$_2$Cd$_{20}$. We find that the lowest energy multiplet of the Pr $4f^2$ valence configuration is a $Γ_3$ non-Kramers doublet and the first excited triplet is a…
