Correlated random fields in dielectric and spin glasses

TL;DR

This paper investigates how intrinsic, correlated random fields in dielectric and spin glasses influence their phase transitions, leading to a crossover rather than a true transition and predicting small impurity domains.

Contribution

It introduces a model of correlated random fields affecting glass behavior, providing predictions for domain sizes and explaining the suppression of glass transitions under certain conditions.

Findings

Random fields suppress the glass transition, causing a crossover instead.

Correlated random fields lead to small impurity 'domains'.

Magnetic fields generate random fields, suppressing spin glass transition.

Abstract

Both orientational glasses and dipolar glasses possess an intrinsic random field, coming from the volume difference between impurity and host ions. We show this suppresses the glass transition, causing instead a crossover to the low $T$ phase. Moreover the random field is correlated with the inter-impurity interactions, and has a broad distribution. This leads to a peculiar variant of the Imry-Ma mechanism, with 'domains' of impurities oriented by a few frozen pairs. These domains are small: predictions of domain size are given for specific systems, and their possible experimental verification is outlined. In magnetic glasses in zero field the glass transition survives, because the random fields are disallowed by time-reversal symmetry; applying a magnetic field then generates random fields, and suppresses the spin glass transition.