Effects of annealing and MgO thickness on perpendicular magnetic anisotropy in Pt/Co₂FeAl_0.5Si_0.5/MgO/Pt multilayers

Magnetic properties have been studied for Ta/Pt/Co₂FeAl_0.5Si_0.5 (CFAS)/MgO/Pt multilayers to investigate the effects of annealing and MgO thickness on perpendicular magnetic anisotropy (PMA). We show that PMA is very sensitive to the annealing conditions and MgO thickness. Strong PMA with high remanence ratio can be achieved after annealing at 300 °C for just 10 min. The thickness of CFAS (t_CFAS) with PMA is strongly dependent on the MgO thickness (t_MgO). A large t_CFAS with PMA is observed to be 4.8 nm for t_MgO = 1.6 nm. The saturation magnetization (M_s) decreases on increasing t_MgO with an obviously periodic oscillation, and the periods of oscillation are between 0.2 and 0.3 nm. Moreover, the annealed structure shows good thermal stability and a weaker temperature dependence of the squareness ratio (M_r/M_s) for the samples with thicker MgO.