Microscopic Origin of Magnetic Anisotropy in Au/Co/Au Probed with X-Ray Magnetic Circular Dichroism

High-field, angle-dependent x-ray magnetic circular dichroism measurements on a Au/Co-staircase/Au structure reveal an anisotropy in the dichroism intensities parallel and perpendicular to the film plane. The size of this effect is related to the anisotropies of the spin density within the Wigner-Seitz cell and of the orbital magnetic moment, both increasing with decreasing Co thickness. The orbital moment anisotropy is shown to be the microscopic origin of the magnetocrystalline energy anisotropy.