Variation of sign and magnitude of the Dzyaloshinskii-Moriya interaction of a ferromagnet with an oxide interface

We demonstrate that both the magnitude and sign of the Dzyaloshinskii-Moriya interaction can be tuned by modifying the type and thickness of an oxide layer adjacent to a ferromagnet. We focus on Ti/Cu/Co90Fe10/Ta(d(Ta))/Oxide/Ta structures, where the Ta interlayer thickness d(Ta) ranged from 0 nm to 3 nm, followed by an exposure to oxygen and "Oxide" can mean CoFeOx and/or TaOx. We used Brillouin light scattering spectroscopy to directly determine the volume-averaged Dzyaloshinskii-Moriya interaction from the nonreciprocity of the spin-wave frequency. The magnitude of the interfacial Dzyaloshinskii-Moriya interaction, D-DMI, ranges from -0.17 to +0.09(+/- 0.02) mJ/m(2), clearly showing a change in both sign and magnitude, with an increase of Ta interlayer thickness. The modification of the oxide interface allows us to systematically change the hybridization of the 3d-CoFe orbitals from 3d-5d to 3d-2p and analyze the influence on the Dzyaloshinskii-Moriya interaction. Importantly, we can vary the Dzyaloshinskii-Moriya interaction while maintaining a relatively small value of the damping parameter.