Correlated random fields in dielectric and spin glasses

¹  Department of Physics and Astronomy, University of British Columbia - Vancouver, B.C., Canada V6T 1Z1
²  Department of Physics, Ben Gurion University - Beer Sheva 84105, Israel
³  Pacific Institute for Theoretical Physics, University of British Columbia - Vancouver, B.C., Canada V6T 1Z1

Corresponding author: smoshe@bgu.ac.il

Received: 6 October 2009
Accepted: 23 November 2009

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.