Impact of interface engineering on domain wall motion in Ta/CoFeB/MgO multilayers with perpendicular magnetic anisotropy

The study investigates the impact of interface engineering on the behaviour of magnetic domain walls (DWs) in perpendicularly magnetized Ta/CoFeB/MgO ultrathin films, for next-generation high-density non-volatile energy efficient memory applications that utilize DW motion. Since perpendicular magnetic anisotropy (PMA) is an interfacial property, the CoFeB interfaces were modified through thermal annealing in the temperature range of 100 to 250 degrees C. It is observed that the multilayer demonstrates PMA up to a temperature of 200 degrees C. Chemical analysis reveals that after annealing, there is diffusion of boron towards MgO leading to the formation of boron oxide along with the reduction of Co-O bonds, which leads to the suppression of PMA along with an increase in coercivity. Furthermore, we examined the velocity of DW driven by an external field within the creep regime through the method of symmetric bubble expansion. Interfacial atomic movement across interfaces induces intermixing, leading to alloy formation. This structural modification enhances the pinning centres, as reflected in the increased roughness of the DWs. This intermixing also led to a significant increase in the creep constant, highlighting the role of interface in controlling DW dynamics.