Quadrupolar Susceptibility and Magnetic Phase Diagram of PrNi$_2$Cd$_{20}$ with Non-Kramers Doublet Ground State

TL;DR

This paper investigates the quadrupolar and magnetic properties of PrNi$_2$Cd$_{20}$ using ultrasonic and high-field measurements, revealing a non-Kramers doublet ground state, quadrupolar fluctuations, and field-induced phase transitions.

Contribution

It provides the first detailed ultrasonic study of PrNi$_2$Cd$_{20}$'s ground state and phase diagram, highlighting quadrupolar effects and magnetic field-induced phenomena.

Findings

Identification of a $b3$ non-Kramers doublet ground state.

Observation of quadrupolar softening below 30 K.

Detection of a magnetic-field-induced phase transition around 26 T.

Abstract

In this study, ultrasonic measurements were performed on a single crystal of cubic PrNi$_2$Cd$_{20}$, down to a temperature of 0.02 K, to investigate the crystalline electric field ground state and search for possible phase transitions at low temperatures. The elastic constant $(C_{11}-C_{12})/2$, which is related to the $\Gamma_3$-symmetry quadrupolar response, exhibits the Curie-type softening at temperatures below $\sim$30 K, which indicates that the present system has a $\Gamma_3$ non-Kramers doublet ground state. A leveling-off of the elastic response appears below $\sim$0.1 K toward the lowest temperatures, which implies the presence of level splitting owing to a long-range order in a finite-volume fraction associated with $\Gamma_3$-symmetry multipoles. A magnetic field-temperature phase diagram of the present compound is constructed up to 28 T for $H \parallel$ [110]. A clear acoustic de Haas-van Alphen signal and a possible magnetic-field-induced phase transition at $H \sim$26 T are also detected by high-magnetic-field measurements.