Large enhanced thermal stability of perpendicular magnetic anisotropy films in magnetic tunnel junctions

For magnetic sensor and magnetic random access memory, the thermally tolerant need to be improved at a relatively high operation temperature. In this work, the correlations between the thermal stability and perpendicular magnetic anisotropy films with different heavy metal layers, structures and CoFeB compositions were investigated in details. It was found that the thin films adopting W or Mo heavy metal layer in the bottom structure, and the thin films adopting Mo heavy metal layer in the top structure exhibit a relatively good operation stability, no matter what the CoFeB composition is. Moreover, the thermally robust perpendicular magnetic anisotropy was obtained in the CoFeB with a relatively large Co atomic composition. According to the element distribution states analysis and oxidation conditions at CoFeB/MgO interface, the reasons are attributed to the structural- and composition-dependent Fe-O bonding. This research helps to design and optimize the ultralow-power and thermally stable magnetic devices based on the suitable heavy metal layers, structures, and CoFeB compositions.