FUNDAMENTAL MAGNETIZATION PROCESSES IN THIN-FILM RECORDING MEDIA

This chapter discusses the magnetic hysteresis, reversal processes, and domain patterns in hard magnetic materials utilized as thin-film recording media. It also presents the results of numerical simulations that exhibit some of the complexities of the magnetic recording technology. In numerical simulations of magnetization patterns and reversal processes in hard as well as soft magnetic materials, the ability to model accurately has been limited by current computational power. The inherent difficulty inaccurate modeling of magnetic systems is the incorporation of the long-range magnetostatic fields. Any reasonable numerical spatial or temporal discretization requires significant computer storage and speed. The simulations exhibit a fascinating interplay between physics and complexity. For example, in a typical in-plane isotropic film, nucleation of magnetization reversal occurs by vortex formation. The expansion of reversed regions during hysteresis is achieved through vortex motion. The vortices are better defined if the magnetostatic interaction strength is large relative to the grain anisotropy; they are larger and more distantly separated if the intergranular exchange coupling is large. Strongly interacting assemblies of magnetic grains exhibit self-organized behavior. © 1992, Academic Press, Inc.