Spin Freezing in Geometrically Frustrated Antiferromagnets with Weak Disorder

TL;DR

This paper studies how weak disorder affects geometrically frustrated antiferromagnets, revealing that random exchange interactions induce a spin glass transition and may explain observed spin freezing phenomena.

Contribution

It demonstrates that weak disorder in exchange interactions leads to long-range effects and spin glass behavior in pyrochlore antiferromagnets, a novel insight into frustration-induced spin freezing.

Findings

Disorder induces long-range effective interactions.

A spin glass transition occurs at a disorder-dependent temperature.

Disorder from random strains can explain spin freezing in experiments.

Abstract

We investigate the consequences for geometrically frustrated antiferromagnets of weak disorder in the strength of exchange interactions. Taking as a model the classical Heisenberg antiferromagnet with nearest neighbour exchange on the pyrochlore lattice, we examine low-temperature behaviour. We show that random exchange generates long-range effective interactions within the extensively degenerate ground states of the clean system. Using Monte Carlo simulations, we find a spin glass transition at a temperature set by the disorder strength. Disorder of this type, which is generated by random strains in the presence of magnetoelastic coupling, may account for the spin freezing observed in many geometrically frustrated magnets.