DMI measurement in ferrimagnetic Mn₄N thin film

Ferrimagnetic Mn4N thin film with perpendicular magnetic anisotropy is a candidate for spintronic devices due to its low magnetization (40-100 emu/cc), high perpendicular anisotropy (7-10 kJ/m³ and large domain wall velocity (~900 m/s). Recently, tunable magnetic skyrmions have been reported in 15nm Mn4N thin films on MgO (100) substrates with Cu_xPt_1-x capping layers, and the interfacial Dzyaloshinskii-Moriya Interaction (DMI) is calculated with density functional theory. Measured DMI is necessary for comprehensively exploring the skyrmions in Mn₄N. However, the DMI of the Mn₄N system is hard to be measured directly with Brillouin light scattering (BLS) due to its large saturation field(>3T). Here, based on magnetic droplet theory, we report the DMI of MgO/Mn₄N(15nm)/Cu_xPt_1-x (x=0, 0.5, 0.9, 1) by extracting the effective field of DMI from angular dependence of anomalous Hall effect. The DMI of the MgO/Mn4N/Cu_xPt_1-x decreases non-linearly as Cu concentration increases. Finally, the possible effect on the DMI of the mixing layer at the surface of Mn₄N is discussed.