Terahertz Faraday rotation induced by an anomalous Hall effect in the itinerant ferromagnet SrRuO3

We report on the observation of Faraday rotation in the terahertz frequency range in a thin film of itinerant ferromagnet, SrRuO3. As optical counterpart of the anomalous Hall effect (AHE), the complex optical Hall conductivity spectrum σxy(ω) was extracted from the Faraday rotation and ellipticity spectrum. The temperature and frequency (ω) dependences of σxy(ω) in the terahertz regime are consistently connected with the dc AHE. A clear resonance structure is identified in the σxy(ω) spectrum right below the Fermi level as the plausible origin of the large dc AHE.