Photoinduced sign inversion of the anomalous Hall effect in EuO thin films

We report on the sign inversion of the anomalous Hall effect (AHE) in EuO thin films along with photoirradiation as well as a temperature scan across ∼25 K that is well below the Curie temperature (TC∼80 K). The former gives an enhancement of the mobile electron density (n) by more than 30%, but the latter gives a negligible modification of n of only 3% with a significant enhancement in mobility. It is found, in addition to the universal scaling law between longitudinal conductivity (σxx) and anomalous Hall conductivity (σAH) as |σAH σxx1.6, that there is a critical value of about 102 Scm-1 in σxx that gives a boundary in the sign inversion of σAH. If n solely governs the sign of σAH, the phenomenon could be explained by a Fermi level shift across the singularity in the band structure. However, our band calculation shows that, within any realistic adjustment of band parameters, the sign inversion of AHE never occurs. Thus, we conclude that other mechanisms of AHE are necessary to account for the AHE of EuO.