Measurement of the Dzyaloshinskii-Moriya Interaction in Mn₄N Films That Host Skyrmions

Mn₄N thin film is one of the potential magnetic mediums for spintronic devices due to its ferrimagnetism with low magnetization, large perpendicular magnetic anisotropy (PMA), thermal stability, and large domain wall velocity. Recent experiments confirmed the existence of tunable magnetic skyrmions in MgO/Mn₄N/Cu_xPt_1-x(x = 0, 0.5, 0.9, 0.95), and density functional theory (DFT) calculation provided a large theoretical value of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) of Mn₄N/Pt, which is consistent with the predicted chemical trend of the DMI in transition metal/Pt films. So far, the measured DMI has not been reported in Mn₄N, which is needed in order to support the predicted large DMI value. This paper reports the average DMI of MgO/Mn₄N(17 nm)/Cu_xPt_1-x(3 nm) extracted from the anomalous Hall effect with various tilted angles, which is based on magnetic droplet theory with DMI effects. The DMI decreases from 0.267 mJ/m² to 0.011 mJ/m² with non-linear tendencies as Cu concentration in the Cu_xPt_1-x capping layer increases from 0 to 1, demonstrating the control of the DMI through the Cu_xPt_1-x capping layer. Furthermore, a solid solution model is developed based on an X-ray photoelectron spectroscopy (XPS) compositional depth profile to analyze the possible effects on the DMI from the mixing layers at the surface of Mn₄N. After taking into account the mixing layers, the large DMI in Mn₄N film with Pt capping is consistent with the predicted DMI.