Field evolution of tilted vortex cores in exchange-biased ferromagnetic dots.

We developed an analytical model for the magnetization reversal via vortex nucleation and annihilation in double-layer ferromagnetic/antiferromagnetic cylindrical dots. The coupling of the ferromagnet to the antiferromagnet is modeled by means of an interfacial exchange field. The nonuniformity of the magnetization reversal mode perpendicular to the layers is explicitly included and results in a tilted vortex core (tilted Bloch line). The vortex core tilt results in an asymmetry of the nucleation and annihilation fields, which are calculated as a function of the dot geometry.