Anomalous Hall effect of facing-target sputtered ferrimagnetic Mn₄N epitaxial films with perpendicular magnetic anisotropy

Epitaxial Mn_4N films with different thicknesses were fabricated by facing-target reactive sputtering and their anomalous Hall effect (AHE) is investigated systematically. The Hall resistivity shows a reversed magnetic hysteresis loop with the magnetic field. The magnitude of the anomalous Hall resistivity sharply decreases with decreasing temperature from 300 K to 150 K. The AHE scaling law in Mn_4N films is influenced by the temperature-dependent magnetization, carrier concentration and interfacial scattering. Different scaling laws are used to distinguish the various contributions of AHE mechanisms. The scaling exponent \gamma > 2 for the conventional scaling in Mn_4N films could be attributed to the residual resistivity \rho_xx0. The longitudinal conductivity \sigma_xx falls into the dirty regime. The scaling of \rho_\rm AH=\alpha \rho_xx0 +b\rho_xx^n is used to separate out the temperature-independent \rho_xx0 from extrinsic contribution. Moreover, the relationship between \rho_\rm AH and \rho_xx is fitted by the proper scaling to clarify the contributions from extrinsic and intrinsic mechanisms of AHE, which demonstrates that the dominant mechanism of AHE in the Mn_4N films can be ascribed to the competition between skew scattering, side jump and the intrinsic mechanisms.