Cluster-glass phase in pyrochlore XY antiferromagnets with quenched disorder

TL;DR

This paper investigates how quenched disorder affects pyrochlore XY antiferromagnets, revealing a transition from ordered states to a cluster-glass phase characterized by magnetic domains and spin clusters due to random anisotropies.

Contribution

It demonstrates that quenched disorder destroys long-range magnetic order, leading to a cluster-glass phase driven by off-diagonal exchange anisotropies, supported by analytical and Monte Carlo methods.

Findings

Long-range order is lost beyond a critical disorder level.

Disorder induces magnetic domains and spin-glass behavior.

Random anisotropies originate from off-diagonal exchange couplings.

Abstract

We study the impact of quenched disorder (random exchange couplings or site dilution) on easy-plane pyrochlore antiferromagnets. In the clean system, order-by-disorder selects a magnetically ordered state from a classically degenerate manifold. In the presence of randomness, however, different orders can be chosen locally depending on details of the disorder configuration. Using a combination of analytical considerations and classical Monte-Carlo simulations, we argue that any long-range-ordered magnetic state is destroyed beyond a critical level of randomness where the system breaks into magnetic domains due to random exchange anisotropies, becoming, therefore, a glass of spin clusters, in accordance with the available experimental data. These random anisotropies originate from off-diagonal exchange couplings in the microscopic Hamiltonian, establishing their relevance to other magnets with strong spin-orbit coupling.