Evidence of the oscillatory magnetic anisotropy in Ni/Co/Ni/Cu(100)

Magnetic anisotropy of Ni/Co/Ni/Cu(100) films was studied by the surface magneto-optical Kerr effect and photoemission electron microscopy. The top Ni and Co films enhance the Curie temperature of the bottom Ni layer so that the magnetic anisotropy of the bottom Ni layer can be studied in the monolayer (ML) regime. In addition, the top Ni and Co film thicknesses were chosen to be close to the spin-reorientation transition (SRT) so that the magnetic anisotropy of the bottom Ni layer manifests in the SRT of the whole film. We found that the magnetization direction of the film oscillates as a function of the bottom Ni thickness with a perpendicular magnetic anisotropy appearing at ∼2 ML of Ni. This result indicates the existence of the oscillatory magnetic anisotropy of the Ni film in the ultrathin regime.