Effect of surface roughness on magnetism of ultrathin Co films

Abstract

Interface roughness effect on magnetic anisotropy of Co/Au are studied by using a Au substrate with "sharp" and "rough" surfaces by means of conventional and depth-resolved XMCD techniques. From the Co L-edge XMCD and sum rule analysis, the critical Co thickness of SRT from in-plane to perpendicular magnetization are found to be shifted from ∼0.8 to ∼1.1 nm by Au capping. We also found the sample with "rough" interface favors in-plane magnetization more than the sample with "sharp" interface. Compared to "sharp" sample, "rough" sample has smaller ml/ms values, and no significant probing-depth dependence is observed. These differences in the magnetic state at the interface between "sharp" and "rough" might be caused by structural changes. Moreover, ml/ms is lager for "sharp" sample especially at the interface. This can be interpreted as a large perpendicular anisotropy at the "sharp" interface, i.e. large Ks, while the magnetic anisotropy of the "rough" sample is determined by K v more than by Ks. © Published under licence by IOP Publishing Ltd.