Progressive magnetic softening of ferromagnetic layers in multilayer ferromagnet-nonmagnet systems and the role of granularity

摘要

We report a study of the structural and magnetic behavior of the topmostmagnetic layer in a ferromagnet-nonmagnet (Co-Au) multilayer system. Glancingangle X-ray diffraction measurements performed on a series of multilayersshowed a gradually increasing degree of amorphization of the topmost magneticlayer with increasing number of bilayers. Concurrently, the magnetic hardnessand magneto-crystalline anisotropy of the top Co layer were found to decrease,as observed by magneto-optical Kerr effect measurements. This magneticsoftening has been discussed in the light of Herzer's random anisotropy model.Micromagnetic simulations of the multilayer system also corroborated theseobservations.