Vortex motion in magnetic disks with different geometric asymmetry

An asymmetric disk achieves control over the clockwise and counterclockwise vortex states in a magnetic disk with an in-plane magnetic field. In this study, the influence of different geometric asymmetry on the vortex motion in 800 nm disks has been studied. The excised angle, defined as half of the center angle corresponding to the excised arc, is flatted varying from 15 degrees to 90 degrees. For each asymmetric degree disk, the vortex motion is investigated through anisotropic magnetoresistance measurement and hysteresis loops recorded by focused magneto-optic Kerr effect magnetometry. The vortex nucleation and annihilation fields show strong dependence and different sensitivity on the asymmetry of disk. An interestingly evident switching mode change is also observed at particular excised angle. Numerical simulations, corresponding to realistically identical system, are calculated and agree well with the experimental results. (C) 2008 American Institute of Physics.