NMR measurements on rare-earth metaphosphate glasses, made over a wide temperature range, have shown that nuclear relaxation is not governed by a single exponential in these systems. A model that incorporates spin diffusion ideas has been developed to explain the results. For the highly doped paramagnetic glass systems, it appears that nuclear spins contributing to the NMR signal are found in distinct regions, which are distinguished by the presence or absence of spin diffusion amongst the nuclear spins. The model satisfactorily accounts for the observations and should be applicable to other paramagnetic systems. Information on the rare-earth-ion spin dynamics may be obtained from the NMR measurements using expressions derived from the model.

• Received 8 July 1997

DOI:https://doi.org/10.1103/PhysRevB.56.R8463