Mössbauer-effect study of the structure and magnetic properties of the Na2O · Li2O · B2O3 · Fe2O3 glass system

Abstract

An investigation of the structure and magnetic properties of amorphous ${\mathrm{Na}}_2$O · ${\mathrm{Li}}_2$O · ${\mathrm{B}}_2$ ${\mathrm{O}}_3$ · ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ by means of Mössbauer, x-ray-diffraction, and magnetic-susceptibility measurements is reported. The glasses contain microcrystalline precipitates for which the x-ray data indicate the particle size increases with iron content. The precipitates appear to be mixtures of simple iron oxides. A more complicated compound, possibly a ferrite having the garnet structure, is also present in some samples. The system displays the superparamagnetic behavior characteristic of fine-particle dispersions. Evidence that the Mössbauer doublet may not be a reliable indicator of the coordination of the iron in these samples is presented and discussed. Relaxation spectra have been calculated and compared with the data.