Electronic structures and reorientation of perpendicular magnetic anisotropy of Co/Au(111) and Co/Pd(111)

We have investigated electronic and magnetic properties of Co thin films epitaxially grown on Au(111) and Pd(111) substrates by spin- and angle-resolved photoelectron spectroscopy. In the Co/Au(111) system, the magnetization direction of Co changes from perpendicular to parallel to the surface at about 6 ML. The origin of the reorientation is qualitatively explained by the increasing contribution of Co 3d orbitals perpendicular to the surface. In the Co/Pd(111) system, the reorientation of the magnetization direction occurs at about 4 ML, the origin of which is explained as being due to the contribution of the upper A₃ band of Co with increase of film thickness as in the case of the Co/Au(111) system. The stronger hybridization between Co 3d and Pd 4d states in the Co/Pd(111) system causes larger binding energy shifts of the A₃ states than in the Co/Au(111) system.