HYDROGEN IN THE A15 COMPOUNDS NB3SN AND NB3AL - A NUCLEAR-MAGNETIC-RESONANCE STUDY

Nuclear magnetic resonance measurements of the Sn-119, Al-27 Knight shifts and the Sn-119, Al-27 and H-1 spin-lattice relaxation rates in the A15-type compounds Nb3SnHx(D-x) (x = 0, 0.7 and 1.2) and Nb3AlHx (x = 0, 2.3) have been performed over the temperature range 10-460K. The low temperature Sn-119 Knight shift and spin-lattice relaxation data indicate that in Nb3SnHx(D-x) the density of electron states at the Fermi level decreases strongly with increasing x. The hydrogen mobility in Nb3Al is found to be much higher than that in Nb3Sn. The behaviour of the proton spin-lattice relaxation rate for Nb3AlH2.3 in a wide range of resonance frequencies (9-90 MHz) can be described by the model using a double-peak distribution of activation energies.