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 betwee n Fe3+ tetrahedral and Fe3+ or Cr3+ octahedral cations belong to the L i0.5FexGa2.5-xO4 and Li-0.5(FeCr)(x)Ga2.5-2xO4 systems. New features, such as the interpretation of the iron(III) electronic spectrum in fer rimagnetic spinels, the influence of the nature of the superexchange i nteractions of the pair excitation processes, and the growth of an ele ctronic transition assigned to Cr3+ + Fe3+ --> Cr4+ + Fe2+ intervalenc e charge transfer at 1.8 eV are reported in this study. (C) 1995 Acade mic Press, Inc.