Perpendicular Magnetic Anisotropy and Dzyaloshinskii-Moriya Interaction at an Oxide/Ferromagnetic Metal Interface

We report on the study of both perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interaction (DMI) at an oxide/ferromagnetic metal (FM) interface, i.e., ${\mathrm{BaTiO}}_{3}$ $(\mathrm{BTO})/\mathrm{CoFeB}$. Thanks to the functional properties of the BTO film and the capability to precisely control its growth, we are able to distinguish the dominant role of the oxide termination (${\mathrm{TiO}}_{2}$ vs BaO) from the moderate effect of ferroelectric polarization in the BTO film, on the PMA and DMI at an oxide/FM interface. We find that the interfacial magnetic anisotropy energy of the $\mathrm{BaO}\text{\ensuremath{-}}\mathrm{BTO}/\mathrm{CoFeB}$ structure is 2 times larger than that of the ${\mathrm{TiO}}_{2}\text{\ensuremath{-}}\mathrm{BTO}/\mathrm{CoFeB}$, while the DMI of the ${\mathrm{TiO}}_{2}\text{\ensuremath{-}}\mathrm{BTO}/\mathrm{CoFeB}$ interface is larger. We explain the observed phenomena by first principles calculations, which ascribe them to the different electronic states around the Fermi level at oxide/ferromagnetic metal interfaces and the different spin-flip process. This study paves the way for further investigation of the PMA and DMI at various oxide/FM structures and thus their applications in the promising field of energy-efficient devices.