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

Effects of such ions as Co
²⁺
, Co
³⁺
, and Fe
²⁺
on the magnetooptical properties of Gd
3
Fe
5
O
12
were investigated. Single crystals in which a portion of Fe
³⁺
ions were substituted by these ions were grown from a molten PbO-PbF
2
flux. It was found that Co
²⁺
ions affected the infrared Faraday rotation remarkably, as well as the visible one, both due to spin-allowed crystal-field transitions. Co
³⁺
ions also affected the infrared rotation, but affected the visible one very little. The crystals which contain Fe
²⁺
ions exhibited no anomalous effect on the Faraday rotation in the infrared region, where a broad absorption occurred due to a charge transfer between Fe
²⁺
and Fe
³⁺
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 Fe
²⁺
ions, but Pb
²⁺
ions which originate from the flux.