Magnetization reversal process of the nanosized elliptical permalloy magnetic dots with various aspect ratios

We have studied systematically the reversal processes of nanosized elliptical dots with various aspect ratios, and found three states of magnetization reversal in micromagnetics simulation results: single vortex, double vortex and vortex-free reversal. Uncontrollable single and double vortex state was observed in dot with small aspect ratio, stable double vortex state in medium aspect ratio and vortex free reversal in large aspect ratio. These varieties of magnetization processes were unified in single vortex state when tilted field was applied.