Evidence of diffusion via collective hopping in metallic supercooled liquids and glasses -: art. no. 220201

We report on measurements of the mass dependence (isotope effect E) of Co diffusion in both the glassy as well as the supercooled liquid states in a Pd40Cu30Ni10P20 glass. The isotope effect, which is a fingerprint of the diffusion mechanism, is very small (<0.1) in both states, suggesting diffusion via highly collective hopping. In particular, E does not change upon isothermal relaxation from the glassy into the supercooled liquid state. Our results lend strong support to the view that even after macroscopic softening of a glass the underlying atomic transport mechanism is still solidlike thermally activated hopping in a considerable temperature range above the caloric glass transition temperature.