The local structure and magnetic interactions between Fe3+ and V4+ ions in lithium–phosphate glasses

Electron Paramagnetic Resonance (EPR) provides a useful tool not only as a probe of local structure and short range order in glasses, but also of magnetic interactions in the glasses containing suitable magnetic ions. We have analyzed the spectra of xFe2O3·(100 − x)[P2O5·Li2O] and x(Fe2O3·V2O5)·(100 − x)[P2O5·Li2O] glass systems, with 0 < x ≤ 50 mol %. [P2O5·Li2O] stands for 50Li2O·50P2O5 glass composition. For samples x > 50 mol % a study indicates the presence of crystalline α Fe2O3 in the glasses. Observed spectra have resonance lines centered at g ∼ 4.3 and g ∼ 2.0 typical for Fe3+ and V4+ ions present in the oxide glasses. For low contend of transition metal (TM) oxides (Fe2O3 or V2O5·Fe2O3) the spectra present a hyperfine structure typical for isolated V4+ ions. With the increasing of TM content, the EPR absorption signal showing hyperfine structure superposed by a broad line without hyperfine structure characteristic for clustered ions. At high TM content, the vanadium hyperfine structure disappears and only the broad line can be observed in the spectra.