NMR spectral densities and two dimensional diffusion in TiS 2 (NH 3) 1.0 and TaS 2 (NH 3) x

Abstract

NMR measurements of proton spin-lattice relaxation times T1 and T1ϱ in the layered intercalation compounds TiS2(NH3)1.0 and TaS2(NH3)x (x = 0.8, 0.9, 1.0) are reported as functions of frequency and temperature (100 K – 300 K). These observations probe the spectral density of magnetic fluctuations due to motions of the intercalated molecules at frequencies accessible to the T1 (4–90 MHz) and T1ϱ (1–100 kHz) measurements. Since the average molecular hopping time (τ) can be changed by varying temperature, different regions of the spectral density can be examined. For T > 200 K, both T−11 and T−11ϱ vary logarithmically with frequency, reflecting the two dimensional character of the molecular diffusion. The temperature dependence of T1 suggests that a more accurate picture of the short time dynamics is required. No dependence of relaxation rate on vacancy concentration is found.