Effects of some transition metal ions on the visible and infrared Faraday rotation of gadolinium iron garnet

Effects of such ions as Co²⁺, Co³⁺, and Fe²⁺on the magnetooptical properties of Gd3Fe5O12were investigated. Single crystals in which a portion of Fe³⁺ions were substituted by these ions were grown from a molten PbO-PbF2flux. It was found that Co²⁺ions affected the infrared Faraday rotation remarkably, as well as the visible one, both due to spin-allowed crystal-field transitions. Co³⁺ions also affected the infrared rotation, but affected the visible one very little. The crystals which contain Fe²⁺ions exhibited no anomalous effect on the Faraday rotation in the infrared region, where a broad absorption occurred due to a charge transfer between Fe²⁺and Fe³⁺ions. In the visible region, however, both the Faraday rotation and the figure of merit were improved. The dominant contributor to this improvement is not likely to be Fe²⁺ions, but Pb²⁺ions which originate from the flux.