Magnetic and magneto-transport properties of Mn4N thin films by Ni substitution and their possibility of magnetic compensation

Ferrimagnets are of interest in spintronics owing to the enhancement of spin transfer and spin-orbit torque in the vicinity of the magnetic compensation point. Here, we study the possibility of achieving compensation at room temperature in Mn4-xNixN films grown on SrTiO3(001) substrates by molecular beam epitaxy. The magnetic and magneto-transport properties of 30-nm-thick epitaxial Mn4-xNixN films (x=0, 0.1, 0.25, and 0.5) were investigated. Ni introduction in Mn4N causes the spontaneous magnetization (M-S) to decrease by 45% at x=0.1 and by 75% at x=0.25. All samples exhibited the perpendicular magnetic anisotropy required for spintronic applications as well as displaying a sharp magnetization reversal. Remarkably, the sign of the anomalous Hall resistivity changed in the samples between x=0.1 and 0.25. Further, the magnetization increased for x=0 and 0.1 and decreased for x=0.25 when the temperature was decreased. Based on these results, we propose that there is a magnetic compensation composition between x=0.1 and 0.25, where the magnetization of Mn4-xNixN becomes zero at room temperature. The small M-S and perpendicular magnetic anisotropy of the Mn4-xNixN thin films, thus, make them suitable candidates for use in spin transfer torque-based devices.