Magneto-Optical Effects of Tetrahedrally Coordinated Co2+ in Ferrites

A large magneto-optical effect near the 0.7 and 1.5 ¿m wavelengths in ferrites containing tetrahedral Co²⁺ ions was studied on the basis of crystal field theory, and the calculated spectrum described herein was found to essentially reproduce the experimentally observed Faraday rotation curves of the Co²⁺ ion substituted ferrites. Eigenstates corresponding to the 0.7 and 1.5 ¿m transitions were determined in the framework of the strong crystal field approximation, using data for the absorption spectra of tetrahedral Co²⁺ ions in the garnets. The strengths of these transitions and the spin-orbit interaction coefficients of the excited states were calculated from the eigenstates. From these parameters, the Faraday rotation spectrum was calculated for the wavelength range from 0.5 to 2.0 ¿m.