EPR and magnetic susceptibility studies of xCuO·(1− x)[2 B2O3· Li2O] glasses

Abstract

The results of EPR and magnetic susceptibility studies on xCuO·(1− x)− [2 B 2 O 3· Li 2 O] glasses with 0⪕x⪕30 mol %, are reported. The modification of EPR spectra with the increasing of CuO content are explained supposing that these are the result of the superposition of two EPR signals, one showing the hyperfine structure typical for isolated Cu 2+ ions and other consisting from a broad line centered at g ∼ 2 typical for the clustered Cu 2+ ions. The values of the EPR parameters prove that the coordination of isolated Cu 2+ -complexes remains approximately the same and show that Cu 2+ ions are situated in axially distorted octahedral vicinities. EPR measurements have shown that the Cu 2+ ions are present mostly as the isolated species when x⪕5 mol %. Beside the dipole-dipole coupling between Cu 2+ ions, the magnetic measurements suggest that for x>10 mol % superexchange interactions appear, too. From Curie constant is established that in this glass system the copper ions are in Cu 2+ and Cu + valence states. Also, the amounts of the copper ions in bivalent state are determined.