Micromagnetics of soft magnetic thin films in presence of defects

We solve numerically the Landau-Lifshitz-Gilbert equation and calculate the magnetization in a magnetic film including a nonmagnetic defect for two initial magnetization states consisting of circular structure with 4 domains and 7 domains. The defect at the vortex wall restrains the magnetization temporarily but the vortex wall comes out of the defect beyond a critical applied field. This critical field increases as the defect size becomes large. The defect at the film side fixes the magnetization at the film edge. The edge defect leads to a reproducible magnetization state inside the film, though a locally stable structure appears for the magnetic thin film without defects. It seems that the defect may improve the stability of the magnetic thin film head.