Asymmetric Reversal in Exchange Bias: experiment and micromagnetic simulations

Asymmetric reversal process in several exchange biased systems is a yet unexplained problem. Recent experimental results on epitaxial FeF$_{2}$/Ni bilayers reveal strongly asymmetrical hysteresis loops. A systematic micromagnetic study based on the assumption of pinned AF moments at the ferromagnetic interface is performed. The simulation result suggests a winding and unwinding of \textit{local} incomplete domain walls in the ferromagnet parallel to the ferro-/antiferromagnet interface at only one side of the saturation is responsible for the asymmetry observed. The simulations are in very good agreement with the experiment results.