The valence states of manganese ion in potassium-borate oxide glasses

Abstract

EPR and magnetic susceptibility measurements have been performed on xMnO·(1- x) [2B 2O 3·K 2O] with 0⩽ x⩽50 mol %. The X-ray diffraction analysis showed that in this glass system homogeneous glasses are formed up to x = 70 mol %. EPR and magnetic susceptibility data have shown that in the glasses with x ⩽ 5 mol % only Mn 2+ ions are present as magnetically isolated species. EPR spectra are modified with the increasing of manganese ions content. In the concentration range 0.5 ⩽ x ⩽ 5 mol %, the spectra are characterized by appearance of three resonance absorptions at g ≅ 4.3 and g ≅ 3.3 without hyperfine structure, and at g ≅ 2.0 with hyperfine structure. For the glasses with x >62; 5 mol %, the resonance spectra are characterized by the appearance of the broad line at g ≅ 2, characteristic for clustered ions. The magnetic susceptibility data suggest the appearance of superexchange interactions for x >62; 5 mol %. From Curie constant values and qualitative chemical analysis we have established that in the glasses with x ⩾ 10 mol % both, Mn 2+ and Mn 3+ ions are present.