LOW-FREQUENCY EXCITATIONS IN FLUORIDE GLASS STUDIED BY NUCLEAR-SPIN RELAXATION AND ELECTRICAL-CONDUCTIVITY

Nuclear spin relaxation (NSR) and electrical conductivity measurements were performed between about 1 K and room temperature in various fluo ride glasses. The F-19 NSR rates are found to exhibit a pronounced pea k around 10 K which is not observed by conductivity experiments. The u nderlying relaxation process is interpreted by magnetic fluctuations b etween neighbouring F-19 nuclear probes without accompanying charge mo tions. The observed NSR rates and conductivities can be described phen omenologically in the context of excitations of asymmetric double well potential (ADWP) configurations intrinsic to the glassy state.