High thermal stability of perpendicular magnetic anisotropy in the MgO/CoFeB/W thin films

Abstract Perpendicular magnetic anisotropy (PMA) with high thermal stability is greatly essential for ultrahigh density and stable data storage devices. Here, the effect of vacuum annealing on PMA of MgO/CoFeB/W stacks was investigated. It was shown that the PMA can be well maintained after annealing at 590 °C, which is much higher than that in traditional Ta-based PMA films. Using the polarized neutron reflectometry, the Co-Fe atoms proportion of the CoFeB/W interface was deliberately determined at different temperatures. It is found that the Co and Fe atoms of CoFeB/W interface had strongly segregation after annealing at 590 °C Furthermore, the effect of different proportion of Co-Fe elements on the PMA was systematically studied by the first-principles calculation. Our first-principles calculation and further analysis reveal that different Co-Fe proportion leads to the modification of orbital hybridization between d xy and d x 2 - y 2 orbitals at the CoFe/W interface, indicating that the interfacial segregation can enhance the PMA. These findings unveil the origin of PMA in W-based devices with high thermal stability and can promote their future industrial applications.