Reflectance−circular dichroism of the magnetic insulator CoxCd1−xCr2S4

Large infrared magneto−optic effects are observed in the series of magnetic compounds CoxCd1−xCr2S4 by means of reflectance−circular dichroism. These effects are associated with the crystal−field transitions of divalent cobalt. Comparison of surface and bulk magneto−optic effects indicate that the surface optical coefficients are representative of bulk phenomena. The magneto−optical effects associated with the 4A2(F) −to−4T1(F) transition are nearly linear with cobalt concentration x. The 4A2(F) −to−4T1(P) transition at about 1.0 μm exhibits a red shift of about 900 cm−1 as x increases from 0.05 to 1.00. Also, the magnitude of the magneto−optic coefficient is not linear in cobalt concentration and reaches a maximum value near x=0.25. The unusual magneto−optical effects associated with the 4T1(P) transition may be utilized in tailoring materials for particular applications.