Magneto-optical properties of substituted cobalt ferrites: CoFe2−<i>x</i>Me<i>x</i>O4 (Me=Rh3+, Mn3+, Ti4++Co2+)

Abstract

The Faraday rotation has been calculated at 1.55-eV photon energy (800 nm wavelength) for various substitutions in CoFe2O4 from the optical constants and the Kerr rotation and ellipticity spectra of polycrystalline bulk samples. The Faraday rotation consists of contributions both from the Co2+→Fe3+ charge transfer transition on octahedral sites as well as from the Co2+ 4A2→4T1 (P) crystal-field transition on tetrahedral sites, both centered around 2-eV photon energy. For the various substitutions the contribution of the crystal field transition to the Faraday rotation at 1.55 eV is determined by the amount of Co2+ on tetrahedral sites as well as the shift in energy of this transition upon substitution. A significant contribution of the 4A2→4T1 (P) transition to the Faraday rotation at 1.55 eV is reached in Rh3+ substituted CoFe2O4.