Elucidate interfacial disorder effects on the perpendicular magnetic anisotropy at Fe/MgO heterostructure from first-principles calculations.

The interfacial perpendicular magnetic anisotropy (PMA) plays a key role in spintronic applications such as memory recording and computational devices. Despite robust PMA being reported at the Fe/MgO interface, there are still inconsistencies in the disorder effects on the interfacial magnetic anisotropy. Here we reported a comprehensive study of the influence of the interfacial disorder, including the underoxidization, overoxidization, and oxygen migration, on the PMA of the Fe/MgO interface using first-principles calculations. Compared to the pristine Fe/MgO interface, the underoxidation at the Fe/MgO interface keeps the interfacial PMA but reduces the interfacial anisotropy constant ( K i ). The overoxidization and oxygen migration at the interface both reduce the K i and even switch the easy magnetization axis from the out-of-plane to in-plane direction at high oxygen percentage. In all the cases, the K i was found strongly correlated to the difference of the orbital magnetic moment along the in-plane and out-of-plane direction. Calculated layer-resolved and orbital-resolved K i revealed that the orbital coupling between the d xy anddx2-y2states of the interfacial Fe layer plays a key role in determining the interfacial magnetic anisotropy. This work provides deep insights into the oxidation effects on the interfacial magnetic anisotropy of Fe/MgO system and a possible avenue to tune the K i via interfacial engineering.