Magnetic anisotropy and X-ray magnetic circular dichroism of MnNi surface alloy: Ab initio studies

The magnetic properties of MnNi surface alloy grown on fcc Co(0 0 1) surface have been explored through the full potential linearized augmented plane wave (FLAPW) method. It has been found that one monolayer (ML) of Mn0.5Ni0.5 alloy on Co(0 0 1) surface has a ferromagnetic (FM) ground state. We suggest that the direct exchange coupling between Mn and Ni plays an essential role for the ferromagnetism. The vertical position of Mn is higher by 0.26 Å than that of Ni, i.e., the surface has a buckling geometry. In contrast to pure fcc Co(0 0 1) film which has in-plane magnetization, we have obtained that the magnetocrystalline anisotropy of MnNi/Co(0 0 1) due to spin-orbit interaction is perpendicular to the film surface and the magnetic anisotropy energy is 146 μeV/cell. In addition, the theoretically calculated X-ray magnetic circular dichroism (XMCD) is presented.