Abstract
The temperature dependence of the spin-lattice relaxation time T1 of 133Cs in CsFeCl3 was measured from 1.5 to 20, K with external fields up to 7, T applied along the c-axis, and the analysis was performed on the basis of the dynamical correlated-effective-field approximation theory. T1-1 below 2, T, which decreases markedly with decreasing temperature, was well interpreted in terms of the longitudinal spin fluctuation characterized by a large energy gap. For higher fields however, T1-1 exhibited an almost temperature-independent behavior accompanied by an significant increase below 5, K. The latter feature was ascribed to the transverse spin fluctuation associated with the softening of the lower branch of the excited doublet around the K-point.
