The direct and Raman spin-lattice relaxation process in YbCl 3·6H 2O

Abstract

Spin-lattice relaxation times are reported for ytterbium chloride hexahydrate. Measurements at strong external magnetic fields showed for a powdered sample a direct process, in numerical agreement with the electron spin-lattice relaxation times calculated from proton spin-lattice relaxation measurements. Studies on a single crystal demonstrated the anisotropic character of the direct process in this salt, although our results were strongly influenced by phonon-bottleneck effects. The temperature dependence of the relaxation process at weak magnetic fields was investigated between 2 and 21 K. These results are described by the T 9 Raman process and not by an Orbach mechanism via the next exited doublet at 197 K as suggested earlier. Summarizing, the paramagnetic spin-lattice relaxation time for powdered YbCl 3·6H 2O can be given by ( H in kOe, T in K): τ −1 = (1.0 ± 0.1) × 10 −2 H 4 T + 0.47 × 10 −8 T 9 J 8 ( θ = 180 K) s −1.