Magnetoelastic mechanism of spin-reorientation transitions at step edges

The symmetry-induced magnetic anisotropy due to monoatomic steps at strained Ni films is determined using results of first-principles relativistic full-potential linearized augmented-plane-wave calculations and an analogy with the Néel model. We show that there is a magnetoelastic anisotropy contribution to the uniaxial magnetic anisotropy energy in the vicinal plane of a stepped surface. In addition to the known spin-direction reorientation transition at a flat Ni/Cu(001) surface, we propose a spin-direction reorientation transition in the vicinal plane for a stepped Ni/Cu surface due to the magnetoelastic anisotropy. We show that with an increase of Ni-film thickness, the magnetization in the vicinal plane turns perpendicular to the step edge at a critical thickness calculated to be in the range of 16-24 Ni layers for the Ni/Cu(1,1,13) stepped surface.