Hydrogen in the A15 compounds Nb 3Sn and Nb 3Al: a nuclear magnetic resonance study

Abstract

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