Vortex annihilation in magnetic disks with different degrees of asymmetry

We investigate the influence of one-side-flat asymmetric degrees on vortex annihilation behavior in different chirality, clockwise or counterclockwise. The vortex annihilation fields are found to depend not only on the vortex chirality but also strongly on the degrees of asymmetry. The sequence of vortex annihilation from the flat to the round edges is observed in low asymmetric disks, and interestingly, the sequence is reversed in high asymmetric disks. Fast and non-contact vortex chirality detection can be realized in high asymmetric disks by analyzing hysteresis loop of focused magneto-optic Kerr effect on vortex annihilation. The experimental results agree well with the micromagnetic simulations.