Structural and magnetic properties of lead-bismuthate oxide glasses containing S-state paramagnetic ions

Electron paramagnetic resonance and magnetic susceptibility measurements on vitreous samples of (100 - x)[4Bi(2)O(3) (.) PbO]xMO and (100 - x)[3Bi(2)O(3) (.) 2PbO]xMO systems, where MO = Fe2O3, MnO or Gd2O3 and x = 1, 5, 10 and 20 mol%, indicate important differences regarding the surrounding, valence state and magnetic interactions of the paramagnetic ions. A tendency to cluster, favoring the devitrification of the matrix, is shown to occur in all cases with increasing MO content, while up to 5 mol% a stabilizing effect on the vitreous lead-bismuthate network is observed. The highest stabilizing effect is observed for gadolinium. Magnetic data suggest an antiferromagnetic interaction between the paramagnetic ions for x greater than or equal to 5 mol% MO. The magnetic moments of the samples indicate that iron and manganese occur in both (II) and (III) valence states. The magnetic moments measured for samples containing gadolinium are in all cases smaller than the value corresponding to free Gd3+ ions and decrease with increasing gadolinium content. The decrease is linear and is more pronounced in the 3Bi(2)O(3) (.) 2PbO glass matrix than in the 4Bi(2)O(3) (.) PbO matrix. In order to explain the lower magnetic moments per atom for Gd 31 ions, a model considering short range interactions is proposed. The model can be considered for all glasses with high paramagnetic ions content. (C) 2003 Elsevier B.V. All rights reserved.