Electronic spectrum and antiferromagnetic A-B interactions between tetrahedral 3d(5) and 3d(5) or 3d(3) octahedral cations in oxidic lithium spinels

The compounds chosen to illustrate the interpretation of ligand field spectra of inorganic solids with A-B antiferromagnetic coupling between Fe3+ tetrahedral and Fe3+ or Cr3+ octahedral cations belong to the Li0.5FexGa2.5-xO4 and Li-0.5(FeCr)(x)Ga2.5-2xO4 systems. New features, such as the interpretation of the iron(III) electronic spectrum in ferrimagnetic spinels, the influence of the nature of the superexchange interactions of the pair excitation processes, and the growth of an electronic transition assigned to Cr3+ + Fe3+ --> Cr4+ + Fe2+ intervalence charge transfer at 1.8 eV are reported in this study. (C) 1995 Academic Press, Inc.