O. Kanert et al., RECENT PROGRESS IN THE AREA OF NMR CHARACTERIZATION OF IONIC TRANSPORT AND RELAXATION IN GLASSES, Journal of non-crystalline solids, 203, 1996, pp. 252-261
Results of temperature and frequency dependence of nuclear spin relaxa
tion (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 activate
d low-frequency excitations (LFEs) of disorder modes intrinsic to the
glassy state. The modes are modelled by asymmetric double-well potenti
al (ADWP) configurations with a suitable density of states of the barr
ier height and asymmetry. Varying the nuclear probe allows the detecti
on of different disorder modes. Above 200 K, NSR is dominated by diffu
sive ionic jumps resulting in an asymmetric NSR rate maximum. Evaluati
on 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 Diet
erich group.