Preisach model study of nonlinear exchange bias in antiferromagnetically coupled bilayers

In this paper, a theoretical study of the exchange bias as a function of the interfacial exchange and the grain structure of an antiferromagnetically coupled (AFC) bilayer media was performed. AFC structures are more convenient for this purpose then conventional exchange bias structures, because the exchange bias effect can be tuned solely through the applied field history without the need for thermal processing. In particular, a phenomenological Preisach-type model of the AFC bilayer media was proposed. Results gave an explanation for the recent experimental observation of nonlinear hysteretic exchange bias, as being caused by non-uniformity in interfacial exchange coupling. The role of the grain structure of the stabilizing layer on the bias field was also discussed in the framework of the proposed model.