SPIN-LATTICE RELAXATION IN MANGANESE FLUOSILICATE

Spin-lattice relaxation times of MnSiF6·6H2O are reported. Non-diluted samples showed a Raman relaxation with τL ∝ T-5 above 10 K, while at helium temperatures τL ∝ T-β with 1 < β < 2 for single crystals and β = 1.0 for a powdered specimen. These results indicate that a direct relaxation process is dominating in the powder, while in the single crystals the relaxation is modified by phonon-bottleneck processes. The observed temperature dependences in the liquid helium range could be described with the assumption that τL = τph at T = 3.5 K. The relaxation times observed in the diluted samples showed an anomalous behaviour in the region of the Raman processes. At helium temperatures no evidence was found that impurities play a rôle such as in the case of Mn(NH4)2(SO4)2·6H2O 3). Measurements of the adiabatic susceptibility reveal b C = 71 × 104Oe2, giving b R = 3.7 × 10-2 K2. © 1969.