Tailoring the magnetic vortex annihilation field in shape asymmetric nanocaps

We investigate the influence of geometrical asymmetry in manipulating the annihilation field of a magnetic vortex in nanocap structures. Geometrical asymmetry in the nanocap controls the annihilation sites and thereby, the annihilation field of the magnetic vortex. Appropriate field sequences via major or minor loops lead to distinct vortex circularities and annihilation fields. The origin of the distinct annihilation field is correlated with the difference in the field-dependent energy barrier for clockwise and counter clockwise vortex annihilation, which in turn arises from the asymmetry in geometry. Further, the study also investigated the impact of thickness of asymmetric nanocaps on the vortex annihilation fields. As the thickness of the hemishell increases, the difference between the energy barriers for vortex annihilation during the major and minor loops increases, leading to a greater difference between the annihilation fields along major and minor loops.