Scaling of anomalous Hall effects in facing-target reactively sputtered Fe4N films

Abstract

The anomalous Hall effect (AHE) in the reactively sputtered epitaxial and polycrystalline γ′-Fe₄N films is investigated systematically. The Hall resistivity is positive over the entire temperature range. The magnetization, carrier density and grain boundary scattering have a major impact on the AHE scaling law. The scaling exponent γ in the conventional scaling of ρ_AH ∝ ρ^γ_xx is larger than 2 in both the epitaxial and polycrystalline γ′-Fe₄N films. Although γ > 2 has been found in heterogeneous systems due to the effects of the surface and interface scattering on AHE, γ > 2 is not expected in homogenous epitaxial systems. We demonstrated that γ > 2 results from residual resistivity (ρ_xx0) in γ′-Fe₄N films. Furthermore, the side-jump and intrinsic mechanisms are dominant in both epitaxial and polycrystalline samples according to the proper scaling relation.