Optical and magneto-optical polar Kerr spectra of Fe3O4 and Mg2+- or Al3+-substituted Fe3O4

The diagonal elements of the dielectric tensor, between 0.5 and 5.0 eV, and the magneto-optical polar Kerr spectra, between 0.7 and 4.0 eV, have been determined for a synthetic crystal of magnetite, Fe3O4 and a systematic investigation of these properties for Mg2+ and Al3+ substitutions has been carried out. From these spectra the off-diagonal elements of the dielectric tensor was calculated between 0.7 and 4.0 eV. Through fitting simultaneously both the diagonal and the off-diagonal elements of this tensor with one set of parameters and consistently for all partially substituted ferrite samples. we were able to resolve the magneto-optital spectrum of Fe3O4 between 0.7 and 4.0 eV. The observed trends in the major transitions upon substitution provide the experimental evidence for intervalence charge transfer and intersublattice charge transfer transitions in Fe3O4.