Magneto-Optical Effects of Tetrahedrally Coordinated Co2+ in Ferrites

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