Abstract
AbstractWe report a nuclear magnetic resonance (NMR) study of slow atomic motions in Zr-Ti-Cu- Ni-Be bulk metallic glasses. The employed 9Be spin alignment echo technique is able to probe Be motions with jump rate below 0.1 Hz. It was found that the Be motion is spatially homogeneous. The jump rate follows a perfect Arrhenius temperature dependence. The measured activation enthalpy of 1.2 eV is nearly identical to that obtained by Be diffusivity measurement using elastic backscattering (EBS); this indicates that energy barriers are the same for short and long range Be motions. The present work provides direct experimental evidences that exclude vacancy-assisted and interstitial diffusion mechanisms for Be motions in these systems. The result is interpreted in terms of the spread-out free volume fluctuation mechanism.
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