Misfit strain and magnetic anisotropies in ultrathin Co films hetero-epitaxially grown on Au/Cu/Si(1 1 1)

Abstract

The relation between misfit strain and uniaxial perpendicular magnetic anisotropy (PMA) has been studied in ultrathin Co single films hetero-epitaxially grown on Au/Cu/Si(1 1 1), by means of spin-wave Brillouin light scattering. The misfit strain in Co was intentionally controlled by the thickness of the Au-interlayer. The interface PMA with Cu-overlayers is proportional to the misfit strain, while the volume PMA is equal to a bulk value. We show Co-thickness dependences of PMA in the atomic-scale thickness region to be thinner than several monolayers (ML). The experimental values of the PMA are smaller than the calculated ones, while assuming constant volume and interface PMAs, when the misfit strain is large. In addition, the interface PMA is largely affected by ultrathin Au-overlayers, which indicate a significant deformation of the Co lattice near the upper interface after forming those overlayers. The interface PMA increases monotonically with increasing Au-overlayer thickness ranging from 1 to 3 ML.