Abstract
Effects of spin-orbit interaction (S.O.) and S4 low symmetry crystal field on the Faraday rotation spectra (FRS) of the tetrahedral Co3+ in magnetic garnets are investigated in the scheme of the crystal field theory. The FRS of the magnetic garnets containing tetrahedral Co2+ and Co3+ are also calculated. In order to explain the observed FRS of the tetrahedral Co3+, (1) the coefficient λ of S.O. having negative sign in the -100∼-160 cm-1 range, and (2) a fairly large low-symmetry field are required.