Abstract
The spin–lattice relaxation processes of the39K and27Al nucleiin KAl(SO4)2·12H2O crystals were studied; we found that these processes can be described by linearcombinations of two and three exponential functions, respectively. From these results, weconclude that the discontinuity in the curve of the spin–lattice relaxation rate nearTc (= 360 K) corresponds to the first-order phase transition of the crystal. In the case of the39K nucleus, the relaxation rate increases as the temperature increases. The relaxation rate of the27Al nucleus decreases belowTc as the temperatureincrease, while above Tc its relaxation rate increases with increasing temperature. The temperature dependences ofthese spin–lattice relaxation rates can be described with the power law . Least square fits of the relaxation rates at temperatures belowTc indicatethat k = 2 for the 39K nucleus and k = 7 for the 27Al nucleus. From these results, we conclude that the39K and 27Al spin–lattice relaxations occur from Raman relaxation processes.
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