Infrared Kerr measurements in ferromagnetic silicon carbide

We measure the infrared (100-1000 meV) polar Kerr angle in ferromagnetic silicon carbide (SiC). The Kerr angle is sensitive to the Hall conductivity $\sigma _{xy}$ and measures the difference of optical responses for left and right circularly polarized light, which makes it a sensitive spectral probe for small changes in the symmetry of the system due to magnetic order. Both neutron-irradiated and Al-doped samples are studied in the 10-300K temperature range. This study provides new insights into the mechanisms by which non-magnetic impurities and defects can produce magnetic order. Strong frequency dependence and hysteresis are observed in the Kerr measurements. Work supported by NSF-DMR1006078.