The magneto‐optic Kerr effect and Faraday rotation of CdCr2S4 for radiation between 0.1 and 4 eV

The complex polar Kerr effect (rotation and ellipticity) of CdCr2S4 has been measured between 1.6 and 4 eV at temperatures between Tc = 84 and 6 °K. Four well separated magneto‐optical transitions have been identified. Two sharp peaks at 2.12 and 2.29 eV are attributed to the Cr3+ crystal field transitions 4A2 → 2T2 and 4A2 → 4T1, respectively. Crystal field parameters satisfying the optical data have been derived. Only one transition at 1.9 eV shows a magnetic red‐shift. It depends on sample‐stoichiometry and doping. The strongest resonance is found at 3.4 eV and is assigned to a charge transfer transition of an electron from a p‐orbital of sulphur to a chromium orbital. The Faraday rotation in the infrared region is also reported and shown to be caused by the charge transfer transition at 3.4 eV.