Observation of anH2T7sin2θRaman spin-lattice relaxation rate in a neodymium salt

Pulse-saturation, linewidth-broadening, and $g$ shift data are presented for yttrium ethyl sulfate containing 1-at.% Nd. Observations were made at microwave frequencies of 16.5 and 9.2 GHz and at temperatures between 1.6 and 29 K. A field-dependent Raman relaxation rate varying as $H^2{T}^7{sin}^2\theta$ is identified and discussed. A previously proposed mechanism, which if valid would explain these data, is shown to be incorrect, and the strength of this observed relaxation mechanism is not understood. The phonon-induced $g$ shift varies as $T^4$. The failure of the Debye model for ethyl sulfates is discussed. The ratio $\frac{T_2}{T_1}$ for the ordinary $T^9$ Raman relaxation process is found to be 2.0 ± 0.14.