EPR and magnetic susceptibility studies of iron ions in 70TeO 2·25B 2O 3·5PbO glass matrix

Abstract

Results of EPR and magnetic susceptibility measurements performed on xFe 2O 3·(1 − x)[70TeO 2·25B 2O 3·5PbO] glasses with 0 < x ≤ 20 mol.% are reported. EPR data suggest a tetragonally distorted octahedral symmetry for Fe 3+ ions. The changes induced in the resonance spectra by increasing of Fe 2O 3 content are explained supposing that the resonance centered at g ≈ 2.0 is due to clustered ions. The composition dependence of g ≈ 2.0 line-width shows prevailing superexchange interactions for x > 1 mol.%. The spectra of the investigated glasses containing up to 3 mol.% Fe 2O 3 presents in addition to the line at g ≈ 4.3 also a weak resonance line at g ≈ 9.79 that denotes the rhombic character of the structural units involving the resonance centers. The paramagnetic resonance data consists with those obtained from magnetic measurements. The Curie constant values indicate that in this glass system the iron ions are in both Fe 3+ and Fe 2+ valence state, the last one representing about 56% from the total iron ions content. For x ≥ 1 mol.% a mictomagnetic type order was evidenced.