ELECTRON-PARAMAGNETIC-RESONANCE OF TRANSITION-METAL IONS IN FLUOROGERMANATE GLASSES

The results of an electron paramagnetic resonance (EPR) study of fluorogermanate glasses (FGG) in the CdGeO3-CdF2-AlF3 system doped with small amounts of transition metals (Ti, V, Mn, Fe, Cu) are presented. The single slightly asymmetric lines at g = 1.937 observed for FGG containing TiO2 differ from those reported for Ti3+ ions in fluoride and oxide glasses by a small peak-to-peak linewidth (about 1.5 mT). The spectrum typical of VO2+ ions in oxide glasses was observed for FGG doped with V2O5. The spin-Hamiltonian parameters resemble those reported for VO2+ in germanate glasses. Only the hyperfine sextet at g similar or equal to 2.0 was found for Mn2+ ions in FGG at frequencies of 9 and 37 GHz. The hyperfine constant depends on the total content of fluorides in FGG and is smaller than in fluoride glasses. The EPR spectra of CU2+ ions in FGG with the content of fluorides lower than 50 mol% are similar to those observed for oxide glasses. At high concentrations of fluorides additional peaks are resolved which can be related to superhyperfine interactions with F-19 nuclei. It is assumed that the structure of FGG is determined by the cadmium germanate skeleton in which fluoride structural groups are dissolved.