Electron spin resonance studies of iron-group impurities in beryllium fluoride glasses

Electron spin resonance investigations have been carried out on unirradiated BeF2 glasses. Two relatively intense resonances were observed in a water-free distilled glass known to contain 49 ppm Ni, 13 ppm Mn, and <20 ppm Fe. One of these was the paramagnetic resonance spectrum of Mn2+. Analysis of the observed 19F superhyperfine structure demonstrated this manganese to occupy distorted octahedral sites in the glass network. The second resonance was shown by temperature and frequency dependence studies, coupled with computer line shape analysis, to be a ferromagnetic resonance signal due to precipitated ferrite phases. The data suggest that these ferrites are somewhat heterogeneous and most likely comprize magnetite-like phases similar to NiFe2O4. An optical extinction curve rising into the ultraviolet with an approximate λ−4 dependence is tentatively ascribed to light scattering by ferrite particles ∼1000 A in diameter.