Magnetization structures in thin-film recording media

A computer simulation study of magnetization configurations in planar isotropic thin-film recording media and their transient behavior during magnetization reversal is presented. Magnetization structures formed during magnetization reversal are characterized for various medium parameters. It is found that a reversed region nucleates by formation of a magnetization vortex. Multiple vortex formation yields elongated reverse domains in the applied field direction. Randomly oriented crystalline easy axes provide natural sites for vortex formation, which are facilitated by magnetostatic interactions. Intergranular exchange coupling significantly enhances vortex motion through which domains expand. Large-size domains occur in exchange coupled films. During a domain expansion, vortex-crosstie pairs can be generated and annihilated. Annihilation of vortices, vortex-crosstie pairs, or vortex-vortex pairs completes local magnetization reversal.