Low temperature isotope effects of hydrogen diffusion in metallic glasses

Snoek-like relaxation peaks of Hydrogen and Deuterium in amorphous Fe80B20, Fe40Ni40P14B6 and Fe91Zr9 are detected. At low H, D concentrations the peaks are near 200 K and show small isotope effects of the average activation energies (anti QH ≅ 0.6 eV, anti QD - anti QH ≤ 10 meV). For higher H, D-contents the peaks shift to lower temperatures around to 120 K and show distinct isotope effects in the activation energies (anti QH ≅ 0.3 eV, anti QD - anti QH ≅ 30 meV) and in the amplitude of the low temperature tails of the relaxation peaks. This points to isotope mass dependent deviations from the Arrhenius law due to nonthermal tunneling processes. (orig.)