NUCLEAR-MAGNETIC-RESONANCE STUDY OF DIFFUSION AND LOCALIZED MOTION OF H(D) ATOMS IN TAV2HX(DX)

Nuclear magnetic resonance measurements of 1H, 2D and 51V spin-lattice relaxation rates T1-1 in TaV2Hx(Dx) (0.22<or=x<or=1.54) have been performed over the temperature range 10-440 K. For all the studied samples the double-peak temperature dependence of T1-1 is observed. The high-temperature relaxation rate maximum is associated with H(D) diffusion, and the low-temperature one is attributed to localised motion of H(D) atoms. The experimental results are analysed to obtain the parameters of the two types of motion as functions of temperature and H(D) content. At 300 K the diffusion rate is found to increase with increasing H(D) concentration. The characteristic period of the localised motion, tau L, exhibits unusual temperature dependence, tau L approximately exp(-T/T0) with T 0 approximately=50 K.