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

TL;DR

This study investigates the electronic heat capacity and energy level splitting of PrNi$_2$Cd$_{20}$ and PrPd$_2$Cd$_{20}$, revealing field-dependent behavior linked to exchange interactions in non-Kramers doublets.

Contribution

It provides the first detailed analysis of magnetic field effects on non-Kramers doublets in these Pr-based compounds, highlighting differences in their heat capacity responses.

Findings

Pr is in a $b3$ non-Kramers doublet ground state.

PrPd$_2$Cd$_{20}$ shows a linear magnetic field dependence of the Schottky anomaly.

Exchange interactions influence the magnetic field dependence of energy level splitting.

Abstract

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 $\Gamma_3$ non-Kramers doublet and the first excited triplet is assumed to be a magnetic $\Gamma_5$. 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.