Theoretical study of the blocking temperature in polycrystalline exchange biased bilayers

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 numerical calculations the dependencies of the blocking temperature on the AF layer thickness, the AF grain size, the hysteresis loop measurement time, the interface exchange coupling, the Curie temperature of the FM layer, the Neel temperature of the AF layer, and the AF uniaxial anisotropy have been obtained. Comparisons of the results with the analytical expressions of the blocking temperature in previous study and with the experimental observations are also provided and discussed. (C) 2004 Elsevier B.V. All rights reserved.