Rare-earth-free Mn4N has attracted increasing attention as a spintronic material thanks to its ferrimagnetism, perpendicular magnetic anisotropy, and controllability of magnetic properties by partial replacement of Mn atoms with other elements. Here, we grew ∼25-nm-thick Mn4− xSn xN epitaxial films ( x = 0–1.4) on MgO(001) substrates by molecular beam epitaxy and investigated their lattice constants and magneto-transport properties. The ratio of the out-of-plane lattice constant c to the in-plane lattice constant a in the Mn4− xSn xN films, c/ a, was less than 1 for x < 0.9, but it changed to more than 1 for x = 1.0. Amazingly, the sign of the anomalous Hall effect changed twice with increasing x. These results suggest that the magnetic structure of the Mn4− xSn xN films varies with Sn composition. Possible mechanisms of the magnetic structure change include magnetic compensation, ferrimagnetic–ferromagnetic phase transition, and the formation of noncollinear magnetic structures.
The antiperovskite ferrimagnet Mn4N has perpendicular magnetic anisotropy and small spontaneous magnetization, both of which are favorable properties for current induced domain wall motion. Previously we have investigated the magnetic structure of 3d-element-doped Mn4N thin films and demonstrated ultrafast domain wall velocities reaching 3000 m s−1 in the vicinity of the magnetic compensation composition of Ni-doped Mn4N at the current density of j = 1.2 × 1012 A m−2 at room temperature (RT). In this study, we investigate the effect of Au doping on the magnetic structure of Mn4N films, and present a composition ratio-dependent sign reversal of the anomalous Hall effect at RT. X-ray magnetic circular dichroism measurement revealed that the magnetic moment of the face-centered Mn atoms of Mn4− xAu xN reversed between x = 0.1 and 0.2, and became parallel to that of the corner-site Mn atoms for x = 0.2 and 0.3. This result suggests that the ferrimagnetic-ferromagnetic phase transition occurred in Au-doped Mn4N epitaxial films as in the In-doped Mn4N epitaxial films.
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