Spin—Lattice Relaxation due to Translational Diffusion in LiBr

Abstract

Nuclear spin—lattice relaxation in LiBr due to translational diffusion of Li ion vacancies has been established from an investigation of the temperature dependence of the relaxation timeT 1. The Li and Br T 1's exhibit minima at different temperatures, and are found to arise from magnetic dipole—dipole and quadrupolar interactions, respectively. Since both relaxation mechanisms are observed in the same crystal environment, the results have been used to compare and correlate the relaxation theories of Torrey and Reif and their extensions to LiBr. The magnitude and temperature dependence of the relaxation are in agreement with theoretical predictions. The effects of vacancies caused by (1) the presence of divalent impurity ions, and (2) intrinsic thermal generation are observed and the activation energies for their formation and diffusion are determined. Additional measurements of line narrowing and ionic conductivity are reported which confirm the properties of the diffusive motion.