Anomalous Hall effect in Fe (001) epitaxial thin films over a wide range in conductivity
We report Hall-effect measurements of epitaxial Fe (001) thin films grown on MgO (001). We have focused on the dependence of the anomalous Hall effect (AHE) in heteroepitaxial structures MgO (001)//Fe(t)/MgO with t=10, 2.5, 2, 1.8, and 1.3 nm. Our results have been interpreted in terms of a recent unified theory of the AHE. We have demonstrated that the thickness and roughness of the Fe layer are control parameters to tune both the longitudinal conductivity sigma(xx) and anomalous Hall conductivity sigma(xy). In this way, we report a crossover from the intrinsic moderately dirty region of conductivities where sigma(xy)=const to the dirty region of poorly conducting materials (sigma(xx)< 10(4) S/cm) where we have found that the relation sigma(xy)proportional to sigma(n)(xx) with n=1.66(4) holds, in good agreement, with the expected universal scaling relationship reported in other ferromagnetic compounds.