A study of the direct spin-lattice relaxation process in three manganese compounds at liquid-hydrogen temperatures

Abstract

Spin-lattice relaxation times of manganese fluosilicate, manganese Tutton salt and manganese sulphate tetrahydrate were obtained from a.c. susceptibility measurements in magnetic fields up to 50 kOe at liquid-hydrogen temperatures. The direct relaxation process was observed in strong magnetic fields, without the inaccuracies due to the phonon bottleneck which usually influences similar experiments at lower temperatures. The relaxation times of the direct process may be given as τ −1 = A H 2 T, with A = 3.2 × 10 −7, 1.5 × 10 −7 and 1.3 × 10 −7 Oe −2 K −1 s −1 for powdered MnSiF 6.6H 2O, Mn(NH 4) 2(SO 4) 2.6H 2O and MnSO 4.4H 2O, respectively. These constants are compared with predictions based on the Waller-Al'tshuler and the Kronig-Van Vleck interaction mechanism, the latter leading to a reasonable agreement with experiment.