Electronic structure and magnetic anisotropy of Co/Au(111): A spin-resolved photoelectron spectroscopy study

We have measured spin- and angle-resolved photoemission spectra of Co thin films epitaxially grown on the Au(111) substrate and investigated their electronic and magnetic properties. At the Co/Au(111) interface, we observed strong mixing between Au 5d and Co 3d states resulting in the spin polarization of Au 5d states and the increase of Co 3d orbitals parallel to the surface, which causes the perpendicular magnetic anisotropy of Co films. The electronic structure of Co thin films in a low-coverage region is different from that of bulk hcp Co and it becomes closer to those of the bulk as film thickness increases. The reorientation of the magnetization direction was observed at about 6 ML, the origin of which is qualitatively explained by the relaxation of the atomic distance of Co perpendicular to the surface.