Magnetization distribution in thin films with perpendicular surface anisotropy

Magnetization patterns and remanence states of thin films with a surface anisotropy normal to the film plane are analyzed. The total film energy integral is expanded to second order to find both equilibrium and nucleation. It is shown that for a given film and applied field a critical surface anisotropy is required for the magnetizations to deviate from initial saturation. Analytic expressions are given for these critical conditions for both in-plane and normal applied field. Remanent state magnetization distributions are shown. For small thickness where the exchange energy keeps the magnetization approximately uniform throughout the film, the out-of-plane component increases monotonically with the magnitude of the surface anisotropy. For larger thicknesses, only a layer near the film surfaces rotates into the normal direction. In this case the nucleation condition for formation of these quasiwalls is independent of the film thickness. For large thicknesses the nucleation field varies quadratically with the surface anisotropy. (C) 1997 American Institute of Physics.