Evolution of non-Kramers Doublets in Magnetic Field PrNi${}_2$Cd${}_{20}$ and PrPd${}_2$Cd${}_{20}$

Abstract

Praseodymium-based 1-2-20 cage compounds Pr$T_2{X}_{20}$ ($T$ 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 $\hat{I}{“}_3$ non-Kramers doublet and the first excited triplet is assumed to be a magnetic $\hat{I}{“}_5$. By analyzing the dependence of the energy splitting between the ground and first excited singlet states on external magnetic field, we found that the maximum in the heat capacity corresponding to the Schottky anomaly in PrPd${}_2$Cd${}_{20}$, unlike PrNi${}_2$Cd${}_{20}$, shows pronounced linear dependence on external magnetic field at higher field values. This effect is associated with the exchange interactions between the field-induced magnetic dipole moments.