Magnetic and Optical Anisotropy in Epitaxial Cobalt Films

Cobalt films were grown by molecular beam epitaxy on CaF2 buffer layers on silicon and showed a variety of magnetic and optical effects. When the substrate is Si(111), CaF2 grows as flat layer with (111) surface and Co grows on it in face centered cubic lattice. Magneto-optical Kerr effect (MOKE) from these structures is isotropic in plane. When the substrate is Si(100), CaF2 growth direction is [110] due to unique properties of CaF2/Si(100) interface. Then CaF2 surface has grooves with {\{}111{\}} facets and cobalt grown on it has in-plane magnetic anisotropy with easy axis along the grooves. The dependence of remanence magnetisation and coercivity on azimuthal angle (between the grooves and field) follows single domain model except the range between 80 to 90 degrees - there is a peak related to crystalographic anisotropy. MOKE from these structures can have different sign depending on incidence angle; this is consistent with calculations of multilayer model. We found that the sign of MOKE can change also versus azimuthal angle, which was unexpected. Physics behind this phenomenon will be presented.