Reversal mechanisms and domain structures in thin-film recording media (invited)

Abstract

Magnetization reversal in longitudinal and perpendicular thin films is studied via computer simulation. Collective micromagnetic processes and the formation of magnetization patterns driven by magnetostatic interactions and intergranular exchange coupling is analyzed. In longitudinal thin films, it is found that a reversal starts by formation of magnetization vortices. The collective formation of vortices yields elongated reverse regions along the direction of the applied field. Intergranular exchange coupling enhances these magnetization structures and results in large-size domains. Reversal of a typical perpendicular film (CoCr) consists of discrete nucleation processes. Each individual process is characterized by a planar chain nucleation mode. These collective micromagnetic processes cause film magnetic properties to be significantly different from those of a simple assembly of noninteracting grains. Medium noise in perpendicular films occurs mainly away from transitions in distinct contrast to longitudinal films in which the noise is concentrated at transition centers. Intergranular exchange coupling increases the medium noise in all films.