Multipolar Phase Transition in the 4$f^2$ fcc lattice compound PrCdNi$_{4}$

Abstract

Transport and magnetic properties of a 4$f^{2}$ fcc lattice compound, PrCdNi$_4$, were studied. The magnetic susceptibility, $\chi(T)$, follows the Curie--Weiss law from 300 K to 20 K, as expected for a free Pr$^{3+}$ ion. As the temperature decreases below 5 K, $\chi(T)$ approaches a constant, indicating van-Vleck paramagnetic behavior. The specific heat, $C(T)$, displays a broad shoulder at around 4 K, which can be reproduced by a doublet triplet two-level model with an energy gap of 12 K. These results suggest a non-magnetic $\Gamma_3$ doublet ground state of the Pr$^{3+}$ ion in the cubic crystalline electric field. $C(T)$ exhibits a peak at $T_{\rm O}$ = 1.0 K and this peak remains robust against magnetic fields up to 5 T. In powder neutron diffraction measurements, no magnetic reflection was observed at 0.32 K $<$ $T_{\rm O}$. Two anomalies at $B$ = 2.1 and 5.3 T in magnetoresistance $\rho(B)$ at 0.05 K likely originate from switching in the order parameter. These results suggest that the phase transition at $T_{\rm O}$ is ascribed to an antiferro-type order of the electric quadrupole or magnetic octupole of the $\Gamma_3$ doublet in the 4$f^2$ fcc lattice.