The manipulations of surface anisotropy and interfacial Dzyaloshinskii–Moriya interaction by an amorphized oxide Ta capping layer

The perpendicular magnetic anisotropy (PMA) and the interfacial Dzyaloshinskii–Moriya interaction (iDMI) energy density in Ta/Pt/Co/plasma-enhanced oxide layer systems are systematically investigated by using the magneto-optical Kerr effect and Brillouin light scattering spectroscopy. The wedge-type top Ta layer is grown and the in-situ plasma-enhanced oxidation process is performed to form an amorphized oxide layer. Consequently, the surface anisotropy energy is significantly reduced in a certain TaO x thickness range and the iDMI energy density is relatively maintained. From these systematic experiments, we reveal that the PMA energy is strongly affected by both top and bottom interfaces, but the contribution from the bottom interface is dominant for the iDMI energy density.