Vortex magnetization reversal in double-layer ferromagnetic/ antiferromagnetic dots

We investigated theoretically the magnetization reversal via vortex nucleation and annihilation in double-layer ferromagnetic/antiferromagnetic cylindrical dots. The influence of the antiferromagnetic layer on the magnetization reversal is accounted for by means of an interfacial, unidirectional exchange field. We consider explicitly a nonuniformity of the magnetization reversal mode along the direction perpendicular to the layers, which gives rise to a nonuniform Bloch line. The vortex annihilation fields, the vortex trajectory, and the average dot magnetization are calculated as functions of the dot geometrical parameters and the external field direction with respect to the exchange-bias field. The calculations are compared with recent experiments.