Magnetic anisotropy and lattice strain in Co/Pt multilayers

Abstract

The correlation is reported between perpendicular anisotropy and in-plane lattice strain in Co/Pt multilayers. (Cox/Pty)n samples, where x, y are the thickness of the individual Co and Pt layers and n is the number of repeats that were prepared by molecular beam epitaxy and studied by means of polar magneto-optic Kerr effect and transmission electron microscopy. Kerr rotation data and electron diffraction experiments show that the largest perpendicular anisotropy and square hysteresis loop occur when x=3 Å while the Pt layers are subjected to about -2% in-plane strain. As Co thickness increases, Co and Pt layers gradually lose coherency and the magnetic anisotropy goes from perpendicular to planar. This is accompanied by a relaxation of lattice strain in both Co and Pt layers. The close relationship between magnetic anisotropy and lattice strain can be explained as magnetoelastic anisotropy or stress anisotropy effect due to lattice mismatch between the adjacent epitaxial layers.