Abstract
The results of nuclear spin-lattice relaxation-time measurements in the laboratory reference frame () and the rotating reference frame (), made on nuclei in Ca crystals doped either with , , or paramagnetic centers, are reported. From 0.25 to 0.36 of the Debye temperature, values of the correlation time are found from minima for ions. Over this range , compared to computed from Leushin's theory. For over 0.15 to 0.19 of the Debye temperature, measurements yield , compared to computed from Leushin's theory. From the data for a -doped Ca crystal, a value of 1.9× /sec for the spin-diffusion constant is computed. From the data for a -doped Ca crystal, is computed to be 1.2× /sec. A NMR measurement of the effective number of paramagnetic centers per unit volume, , increases the measured to 2.6× /sec. The computed value of (Lowe and Gade) is 5.1× /sec. Indirect evidence leads to the conclusion that the spin-diffusion barrier radius is at least a factor of 2 smaller than predicted by Rorschach's formula. In the short- region, and , are found to be field-independent, with . The experimental data are consistent with (diffusion-limited region), (diffusion-vanishing region). The initial decay of the magnetization in the measurements of is found to be proportional to in the long-correlation-time region. The coefficient of is used to obtain an experimental value for that is ½ as large as the value supplied by the manufacturer of the crystal.
- Received 13 September 1967
DOI:https://doi.org/10.1103/PhysRev.166.292
©1968 American Physical Society