Nuclear magnetic resonance study of the dihydride phase of the Ti-V-H system

Abstract

We report the results of nuclear magnetic resonance (NMR) measurements of 1. (1) the line shape, the second and fourth moments and the spin-lattice relaxation of the 1H resonance, and 2. (2) the Knight shift and spin-lattice relaxation of the 51V resonance in the dihydride phase Ti 1− x V x H 2 (0.04 ⩽ x ⩽ 0.65). The X-ray and magnetic susceptibility data are also reported. A two-line system was observed in both the 1H and 51V NMR spectra for x = 0.65 indicating that the range of existence of the single dihydride phase in vanadium-rich dihydrides is much narrower than reported previously. Comparison of the experimental and theoretical values of the linewidth and the second and fourth moments of 1H NMR shows that the dipolar interaction is the main source of the line broadening. The temperature dependence of the 1H value T 1 T and the magnetic susceptibility in dilute vanadium hydrides is interpreted in terms of the transition from an f.c.c. phase to a face-centred tetragonal phase induced by the Jahn-Teller effect. Comparison of the values of vanadium Knight shifts in Ti 1− x V x H 2 with existing data for the titanium Knight shift in TiH 2 strongly suggests that the local densities of states at titanium and vanadium sites in the dilute vanadium hydrides Ti 1− x V xH 2 are different. Opposite dependences of the 1H and 51V spinlattice relaxation rates on the vanadium concentration support this suggestion.