Vortex dynamics in submicron exchange-biased disks

Using micromagnetic simulation we have investigated the vortex dynamics in an exchange-biased permalloy nanodisk with 500 nm-radius and 10 nm-thickness. We found the exchange bias plays an important role in the vortex dynamics. The exchange bias results in the elliptical trajectory. The vortex dynamics in the exchange-biased nanodisk is strongly affected by the angle between the exchange bias field and the external field. We found that it is possible to selectively transform the vortex state into the single domain state with a pulsed magnetic field by controlling the magnitude and the angle of the external magnetic field.