Double magnetization reorientation in epitaxial Cu/Ni/Cu/Si(111) ultrathin films

We have deposited epitaxial Cu/Ni/Cu sandwiches on the 7×7 reconstructed surface of single-crystal (111)-Si substrate with nominal Ni thickness in the range between 10 and 60A°. Brillouin light scattering from thermally excited spin waves and surface magneto-optic Kerr effect magnetometry show that the preferred direction of the magnetization is perpendicular to the film plane for Ni film thicknesses between 15 and 30A° , while it is aligned along the film plane for both thicker and thinner films. The observed double reorientation transition is interpreted in terms of a competition between the magnetostatic energy term (shape anisotropy) and both the magnetoelastic and magnetocrystalline anisotropy energy contributions.