Temperature dependence of the nuclear spin-lattice relaxation time in CaF_:Nd

Measurements of the F19 nuclear spin-lattice relaxation time T1 have been made in doped calcium fluoride over the temperature range extending from 300°K down to about 2°K. The doping element was the rare earth neodymium. Data were obtained by a pulsed nuclear resonance method for two orientations of the crystal with respect to the magnetic field. The experimental results were analyzed by means of a general expression for T1 valid for intermediate cases as well as for the diffusion limited and rapid diffusion limits. Dependence of the barrier radius on the temperature and the relaxation time of the paramagnetic impurity is taken into account in this expression. There is reasonable agreement between the experimental measurements and the theoretical expression over the entire temperature range