Theory of the blocking temperature in polycrystalline exchange biased bilayers based on a thermal fluctuation model

Abstract

It is well known that the exchange bias between an antiferromagnet (AF) and a ferromagnet (FM) vanishes at a temperature called the “blocking” temperature. The blocking temperature of polycrystalline exchange biased bilayers is theoretically studied on the basis of a thermal fluctuation model, from which an analytic expression for the blocking temperature as a function of the AF thickness and the AF grain size is obtained for a thin AF layer. This study also gives a quantitative understanding of the relationship of the blocking temperature to the Néel temperature of the AF and the Curie temperature of the FM.