The effect of interfacial oxygen migration on the PMA and thermal stability in MTJ with double MgO layers

Abstract The control of the interfacial oxidization between metal and oxide by oxygen migration is highly effective in tailoring the interfacial microstructure and consequently their physical, chemical and magnetic properties in the magnetic films. Here, we study the effect of a Mo-spacer on the Ta/MgO/CoFeB/Mo/CoFeB/MgO/Ta films to ensure their perpendicular magnetic anisotropy (PMA) for the film after annealing at 500 °C. High-resolution transmission electron microscopy (HRTEM) shows that the MgO layers are mainly uncrystallized and energy dispersive X-ray spectroscopy (EDS) shows there is a significant diffusion of the small amount of Mo elements. The X-ray photoelectron spectroscopy (XPS) indicates that some MgO compounds are reduced to metallic Mg after annealing. More Fe and Co oxides are formed as oxygen reduced from MgO combines with Fe and Co in the CoFeB layer, which strengthens the PMA. The control of oxygen migration is therefore demonstrated as an effective way to improve magnetic properties.