Relaxation Time Measurements in Ruby by a dc Magnetization Technique

Abstract

Relaxation-time measurements by observation of the recovery of the $z$ component of the dc magnetization have been carried out in ruby. Harmonic cross-relaxation processes, involving two, four, and five spins, have been identified. The cross-relaxation time for the five-spin process is found to be proportional to $f^{-2.6\mathrm{}}$, where $f=\mathrm{Cr}:\mathrm{Al}$ atom ratio. The spin-lattice relaxation time is proportional to $f^{-1\mathrm{}}$ for small $f$, but decreases faster at higher concentrations. The temperature dependence as $T^{-1\mathrm{}}$ or $T^{-2\mathrm{}}$ can be explained by a model of cross relaxation between single ions and exchange coupled pairs. The magnetic field dependence is small.