Abstract
Nuclear magnetic resonance measurements of the protonspin-lattice relaxation rate T1-1 for A15-type Nb3AlHx(x = 0.13, 1.77 and 2.75) have been performed over thetemperature range 20-420 K and the resonance frequency range13-90 MHz. The experimental results are analysed to evaluate theelectronic (Korringa) contributions to T1-1 and the parametersof hydrogen diffusion. It is found that the electronic contributionto the relaxation rate decreases with increasing H content. Theeffective activation energies for H diffusion derived from thehigh-temperature relaxation rate data are 0.21 eV for x = 0.13and 0.30 eV for x = 1.77 and 2.75. The behaviour of T1-1at low temperatures (T<270 K for x = 1.77 and 2.75) suggestsa coexistence of at least two frequency scales of H hopping. It isshown that the structure of the sublattice of interstitial dsites (partially occupied by hydrogen) is consistent with thecoexistence of two characteristic jump rates for H atoms.
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