Saturation Effects in Moderately Diluted Cesium Chromium Alum

The steady-state saturation method was used to investigate the paramagnetic relaxation of the chromium ion in cesium chromium (aluminum) sulfate at 24 kMc/sec and at liquid-helium temperatures. The relaxation behavior was studied as a function of the intensity of the microwave field, the temperature, the magnetic-ion concentration, and the spin transition. For the power range used, a single relaxation parameter was found adequate to describe the saturation behavior. The Cr/Al ion concentration was varied between $\frac{1}{0}$ and $\frac{1}{93}$. For each of the spin transitions investigated, it was found that the relaxation parameter increased with magnetic dilution. For all of the samples tested, the temperature dependence of the relaxation parameter $T_1$ in the range 1.6° to 4.2°K could be expressed by the relation $T_{1}T=\mathrm{const}$. The results suggest that for these samples the direct process spin-lattice interaction is the dominant energy bottleneck and that more energy-transfer paths are available at the higher magnetic concentrations.