Reverse magnetic vortex curling direction of ferromagnetic nanodisk

We reverse the magnetic vortex curling direction of ferromagnetic nanodisk by applying a circular Oersted field. The nanodisk is fabricated without breaking its symmetry. The Oersted field is induced by passing current through an atomic force microscope tip placed at the center of the disk. Micromagnetic simulation indicates that compared to the uniformly distributed current throughout the cross section of disk, the line current concentrated in the center can reverse the chirality more easily, which is in accordance with our experimental results.