Candidate quantum spin ice in the pyrochlore Pr$_2$Hf$_2$O$_7$

TL;DR

This study investigates Pr$_2$Hf$_2$O$_7$, revealing quantum spin ice behavior with Ising anisotropy, ferromagnetic correlations, and quantum fluctuations at very low temperatures, suggesting a new candidate for quantum spin ice materials.

Contribution

The paper reports the discovery of quantum spin ice behavior in Pr$_2$Hf$_2$O$_7$, highlighting its non-Kramers doublet ground state and quantum fluctuations, which are novel in this compound.

Findings

Development of ferromagnetic correlations below 0.5 K

Observation of a discrete inelastic excitation indicating spin dynamics

Identification of quantum fluctuations related to cooperative behavior

Abstract

We report the low temperature magnetic properties of the pyrochlore Pr$_2$Hf$_2$O$_7$. Polycrystalline and single-crystal samples are investigated using time-of-flight neutron spectroscopy and macroscopic measurements, respectively. The crystal-field splitting produces a non-Kramers doublet ground state for Pr$^{3+}$, with Ising-like anisotropy. Below 0.5 K ferromagnetic correlations develop, which suggests that the system enters a spin ice-like state associated with the metamagnetic behavior observed at $\mu_0H_c\sim2.4$~T. In this regime, the development of a discrete inelastic excitation in the neutron spectra indicates the appearance of spin dynamics which are likely related to cooperative quantum fluctuations.