ELECTRON-PARAMAGNETIC-RESONANCE AND MOSSBAUER-EFFECT STUDIES IN IRON-DOPED FE-57 ISOTOPE ENRICHED PHOSPHATE-GLASSES

Electron paramagnetic resonance and Mossbauer spectroscopy measurement s of phosphate glasses doped with Fe-57 isotope enriched Fe2O3 have be en carried out. The electron paramagnetic resonance spectra have been computer simulated using an approach based on the eigenfield method ap plied to the 'rhombic' spin Hamiltonian, which contains only the Zeema n and quadrupole fine structure terms, In order to account for the str uctural disorder in glass, different distribution densities of fine st ructure parameters D and E have been tried: a two-dimensional Gaussian function of D and lambda = \E/D\ and 'Czjzek's and related functions' . An agreement between the experimental and computer simulated spectra found with the Gaussian distribution density suggests the presence of a large fraction of Fe3+ sites with axial or feebly rhombic distortio ns (lambda less than or equal to 0.08), The mean value of the axial fi ne structure parameter D is consistent with a highly distorted environ ment of Fe3+ ions in the phosphate glasses (but somewhat less in compa rison with the berate glasses), It is shown that the g(ef) = 2.0 absor ption in the phosphate glasses consists of two different features: a n arrow one results from Fe3+ ions isolated in the glass matrix, while t he broad one is due to crystallite inclusions.