Spin glass transition in geometrically frustrated antiferromagnets with weak disorder

TL;DR

This paper investigates how weak exchange randomness in geometrically frustrated antiferromagnets induces a spin-glass transition, using theoretical replica methods and Monte Carlo simulations, revealing universality with conventional spin glasses.

Contribution

It introduces a theoretical framework for the spin-glass transition caused by weak disorder in frustrated antiferromagnets and maps defect models to pseudospin systems with dipolar interactions.

Findings

Weak exchange randomness favors specific ground states.

Induces a spin-glass transition at a temperature related to disorder strength.

Monte Carlo simulations support the theoretical predictions.

Abstract

We study the effect in geometrically frustrated antiferromagnets of weak, random variations in the strength of exchange interactions. Without disorder the simplest classical models for these systems have macroscopically degenerate ground states, and this degeneracy may prevent ordering at any temperature. Weak exchange randomness favours a small subset of these ground states and induces a spin-glass transition at an ordering temperature determined by the amplitude of modulations in interaction strength. We use the replica approach to formulate a theory for this transition, showing that it falls into the same universality class as conventional spin-glass transitions. In addition, we show that a model with a low concentration of defect bonds can be mapped onto a system of randomly located pseudospins that have dipolar effective interactions. We also present detailed results from Monte Carlo simulations of the classical Heisenberg antiferromagnet on the pyrochlore lattice with weak randomness in nearest neighbour exchange.