Strong Magneto-Optical Effects In Acr(2)O(4) (A = Fe, Co) Spinel Oxides Generated By Tetrahedrally Coordinated Transition Metal Ions

Magneto-optical effects have been investigated over the infrared visible spectral range in ACr(2)O(4) ( A = Fe, Co) spinel oxides with noncollinear spin orders in their ground states. We found large magneto-optical Kerr rotation and ellipticity at the on-site d-d transitions of the A(2+) ions located within the charge gap. The magneto-optical Kerr rotation of upsilon(Kerr) approximate to 12 degrees observed in CoCr2O4 is unprecedentedly large among magnetic semiconductors and points toward the uniqueness of tetrahedrally coordinated Co2+ ions in generating strong magneto-optical response. Criteria of strong magneto-optical effects emerging at on-site d-d transitions of transition metal ions are discussed.