Recent progress in the area of NMR characterization of ionic transport and relaxation in glasses

Results of temperature and frequency dependence of nuclear spin relaxation (NSR) are presented for different inorganic glasses between about 1 K and the glass transition temperature. Below about 200 K the data can be interpreted consistently in the framework of thermally activated low-frequency excitations (LFEs) of disorder modes intrinsic to the glassy state. The modes are modelled by asymmetric double-well potential (ADWP) configurations with a suitable density of states of the barrier height and asymmetry. Varying the nuclear probe allows the detection of different disorder modes. Above 200 K, NSR is dominated by diffusive ionic jumps resulting in an asymmetric NSR rate maximum. Evaluation of the data is shown to agree best with results of Monte Carlo (MC) simulations of the hopping process as performed by the Bunde and Dieterich group.