Slow Spin Relaxation and Low-Temperature Spin Freezing in Disordered Fluorite Ho$_2$Zr$_2$O$_7$

TL;DR

This study investigates the spin freezing phenomena in disordered Ho$_2$Zr$_2$O$_7$, revealing slow spin dynamics, field-induced relaxation, and a low-temperature spin-frozen state, with insights into relaxation processes similar to canonical spin ice systems.

Contribution

It provides new experimental evidence on the origin of spin freezing and relaxation processes in disordered Ho$_2$Zr$_2$O$_7$, expanding understanding of spin ice behavior in this material.

Findings

No long-range magnetic order down to 280 mK

Presence of slow spin dynamics and field-induced relaxation

Identification of two distinct spin relaxation processes

Abstract

We report on the origin of spin freezing in the disordered fluorite Ho$_2$Zr$_2$O$_7$. The system is investigated by low-temperature heat capacity as well as by DC and AC magnetization. While the system does not show a long-range magnetic order down to at least $T = 280$~mK, we observe signatures of slow spin dynamics, magnetic field induced relaxation processes at relatively high temperatures, and a spin-frozen state below $T = 0.6$~K. Our results suggest that similar to the canonical spin ice systems Ho$_2$Ti$_2$O$_7$ [Ehlers 2004] and Dy$_2$Ti$_2$O$_7$ [Snyder 2001], spin freezing in Ho$_2$Zr$_2$O$_7$ is preceded by two slow spin relaxation processes; the first forms a field-induced region extending to at least 18~K and the second is rather field-independent and appears at $T_{\mathrm g2} = 1$~K [Ramon 2020].