Micromagnetic simulation of asymmetric magnetization reversal in exchange biased bilayers

Hysteresis loops were calculated for a model with ferromagnetic grains spin-flop coupled to interacting antiferromagnetic grains with randomly distributed easy axes. The interface between these two layers is assumed to be fully compensated. Field cooling simulated by a Monte-Carlo algorithm and subsequent calculation of the hystersis loop reveals asymmetries in the ascending and descending part of the hysteresis loop, respectively. On the descending branch a steep change of the magnetization can be observed. On the ascending branch homogeneous rotations of the magnetization cause a smoother change of the magnetization. The strong asymmetries vanish after a few hysteresis loop calculations.