Abstract
Electron paramagnetic resonance and magnetic susceptibility measurements on vitreous samples of (100− x)[4Bi 2O 3 · PbO] xMO and (100− x)[3Bi 2O 3 · 2PbO] xMO systems, where MO=Fe 2O 3, MnO or Gd 2O 3 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⩾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 Gd 3+ ions and decrease with increasing gadolinium content. The decrease is linear and is more pronounced in the 3Bi 2O 3 · 2PbO glass matrix than in the 4Bi 2O 3 · PbO matrix. In order to explain the lower magnetic moments per atom for Gd 3+ ions, a model considering short range interactions is proposed. The model can be considered for all glasses with high paramagnetic ions content.
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