Interdiffusion in epitaxial ultrathin Co 2 FeAl/MgO heterostructures with interface-induced perpendicular magnetic anisotropy

The interfacial atomic structure of epitaxial ultrathin Co 2 FeAl/MgO(001) heterostructures, which is related to the interface-induced perpendicular magnetic anisotropy (PMA), was investigated using scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray magnetic circular dichroism. Al atoms from the Co 2 FeAl layer significantly interdiffused into MgO, forming an Al-deficient Co–Fe–Al/Mg–Al–O structure near the Co 2 FeAl/MgO interface. This atomic replacement may have enhanced the PMA, which is consistent with the observed large perpendicular orbital magnetic moments of Fe atoms at the interface. This work suggests that control of interdiffusion at ferromagnet/barrier interfaces is critical for designing an interface-induced PMA system.