H-1 nuclear magnetic resonance and Gd3+ electron spin resonance studies ofwater molecular and electron spin dynamics in Sm(NO3)(3)center dot 6H(2)O

The H-1 nuclear magnetic resonance (NMR) spin-lattice relaxation time (TI), the spin-lattice relaxation time in a rotating flame (T-1p), Gd3+ electron spin resonance (ESR) spectra and differential thermal analysis (DTA) were measured for Sm(NO3)(3). 6H(2)O. A new thermal anomaly was detected by DTA at 183 K during the heating process. The temperature dependence of TI, coul d be explained by the motion of four kinds of water molecule. The activatio n energies and the correlation times at infinite temperature for each water molecule were estimated from T-1p. In phase III, hysteresis of T-1p, which is considered to be caused by the crystallization water molecules, was obs erved. From the results of H-1-NMR T-1 and doped Gd3+ ESR spectra, the elec tron spin-lattice relaxation of Sm3+ proved to be dominated by the Orbach p rocess which occurs through the second excited state caused by the crystal field. (C) 1998 Elsevier Science Ltd. All rights reserved.