Domain state model for exchange bias

Monte Carlo simulations of a system consisting of a ferromagnetic layer exc hange coupled to a diluted antiferromagnetic layer described by a classical spin model show a strong dependence of the exchange bias on the degree of dilution in agreement with recent experimental observations on Co/CoO bilay ers. These simulations reveal that diluting the antiferromagnet leads to th e formation of domains in the volume of the antiferromagnet carrying a rema nent surplus magnetization which causes and controls exchange bias. To furt her support this domain state model for exchange bias we study, in the pres ent article, the dependence of the bias field on the thickness of the antif erromagnetic layer. It is shown that the bias field strongly increases with increasing film thickness and eventually goes over a maximum before it lev els out for large thicknesses. These findings are in full agreement with ex periments. (C) 2001 American Institute of Physics.