Magnetic properties of a Pt/Co₂FeAl/MgO structure with perpendicular magnetic anisotropy

Microstructures and magnetic properties of Ta/Pt/Co₂FeAl (CFA)/MgO multilayers are studied to understand perpendicular magnetic anisotropy (PMA) of half-metallic full-Heusler alloy films. PMA is realized in a 2.5-nm CFA film with B2-ordered structure observed by a high resolution transmission electron microscope. It is demonstrated that a high quality interface between the ferromagnetic layer and oxide layer is not essential for PMA. The conversions between in-plane anisotropy and PMA are investigated to study the dependence of magnetic moment on temperature. At the intersection points, the decreasing slope of the saturation magnetization (M_s) changes because of the conversions. The dependence of M_s on the annealing temperature and MgO thickness is also studied.