Electron paramagnetic resonance and Mossbauer effect studies in iron-doped Fe-57 isotope enriched phosphate glasses
Résumé
Electron paramagnetic resonance and Mössbauer spectroscopy measurements of phosphate glasses doped with 57Fe isotope enriched Fe2O3 have been carried out. The electron paramagnetic resonance spectra have been computer simulated using an approach based on the eigenfield method applied to the ‘rhombic’ spin Hamiltonian, which contains only the Zeeman and quadrupole fine structure terms. In order to account for the structural disorder in glass, different distribution densities of fine structure parameters D and E have been tried: a two-dimensional Gaussian function of D and 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 distortions (λ ≤ 0.08). The mean value of the axial fine structure parameter D is consistent with a highly distorted environment of Fe3+ ions in the phosphate glasses (but somewhat less in comparison with the borate glasses). It is shown that the gef = 2.0 absorption in the phosphate glasses consists of two different features: a narrow one results from Fe3+ ions isolated in the glass matrix, while the broad one is due to crystallite inclusions.