Overlayer-induced anomalous interface magnetocrystalline anisotropy in ultrathin Co films

The full-potential linearized augmented-plane-wave method with the atomic force approach has been used to determine the interface structure and magnetocrystalline anisotropy (MCA) of a Co monolayer on Cu(111), with and without Cu overlayers. It is found in good agreement with experiment, that the interface MCA for a fully relaxed structure is in-plane with a value of -0.30 meV for Co monolayer (ML) on Cu(111). When capped with nonmagnetic Cu, the interface MCA changes dramatically: for one ML Cu coverage, it is perpendicular to the film plane with a MCA value of + 0.23 meV; for two ML Cu coverage, it rapidly drops to -0.02 meV. Our results confirm that the hybridization at the Co/Cu interface plays an important role in the interface MCA of Co/Cu systems. By comparing the results of the fully relaxed structures with those of unrelaxed structures, we also found that relaxation is important for accurate determinations of the interface MCA.