XANES, X-ray photo-electron and optical spectra of divalent nickel at the crystallographic transition in NiCr2O4and the Ni1-xCuxCr2O4system: correlation with the Jahn-Teller effect

Abstract
XANES, X-ray photo-electron and optical spectra of divalent nickel in NiCr2O4 and Ni1-xCuxCr2O4 compounds are reported. The characteristic parameters of the Ni(II)tetra-O chemical bond in spinels are not very sensitive to the Jahn-Teller effect. The tetragonal distortion c/a1-xCuxCr2O4 system for the range 0.22+ spin-orbit coupling and the Cu2+ Jahn-Teller effect.