Surface Anisotropy Energies of Thin Magnetic Films

Abstract

The shape of the surface anisotropy energy surface of a thin magnetic film is investigated. By generalizing the exchange boundary condition to include the cases of unequal spin pinning at the two surfaces of a film, calculations of the spin‐wave resonance spectrum were made and compared with the results of surface oxidation experiments. It was found that the surface anisotropy is uniaxial with the easy axis perpendicular to the surface of the film: the surfaces of the film being hard planes of magnetization. In addition to the ordinary volume spin‐wave resonance modes due to spin pinning, we found also a set of surface modes whose rf component of the magnetization decreases rapidly from the surface toward the interior of the film. Several surface spin‐pinning mechanisms have been proposed. The implications of these proposals are examined in light of our theoretical and experimental results.