Infrared anomalous Hall effect in SrRuO3: Exploring evidence for crossover to intrinsic behavior

The origin of the Hall effect in many itinerant ferromagnets is still not resolved with an anomalous contribution from the sample magnetization that can exhibit extrinsic or intrinsic behavior. We report the midinfrared (MIR) measurements of the complex Hall (theta(H)), Faraday (theta(F)), and Kerr (theta(K)) angles, as well as the Hall conductivity (sigma(xy)) in a SrRuO3 film in the 115-1400 meV energy range. The magnetic field, temperature, and frequency dependence of the Hall effect is explored. The MIR magneto-optical response shows very strong frequency dependence including sign changes. Below 200 meV, the MIR theta(H)(T) changes sign between 120 and 150 K, as is observed in dc Hall measurements. Above 200 meV, the temperature dependence of theta(H) is similar to that of the dc magnetization and the measurements are in good agreement with predictions from a band calculation for the intrinsic anomalous Hall effect (AHE). The temperature and frequency dependence of the measured Hall effect suggests that whereas the behavior above 200 meV is consistent with an intrinsic AHE, the extrinsic AHE may play an important role in the lower-energy response.