MAGNETIC ANISOTROPIES IN BODY-CENTERED-CUBIC COBALT FILMS

The origin of magnetic anisotropies in thin bcc cobalt films is invest igated using Brillouin light scattering. The in-plane directional and wave-vector dependence of surface and bulk magnon frequencies in (110) and (001) oriented films indicate a twofold anisotropy in these cubic ferromagnets with the easy axis of magnetization lying in plane along [001] and [100], respectively. Using elastic constants determined fro m phonon dispersion measurements, we argue that the observed uniaxial anisotropy can be largely accounted for by magnetoelastic interactions driven by lattice mismatch at the film/substrate interface. The easy axis is also evident by the transformation of the surface spin wave in to the n=0 bulk magnon when the magnon wave vector lies parallel to th e spontaneous (easy) axis of magnetization.