The isotope effect for Co diffusion in a highly supercooled melt was measured by using 57Co and 60Co radio-tracers (table 23). The isotope effect was only of the order of 0.09, and exhibited no significant temperature dependence at up to 120K above the glass transition temperature. This covered almost 3 orders of magnitude of diffusivity. The results suggested that long-range diffusion in the highly supercooled melt was not mediated by viscous flow but rather proceeded via collective hopping processes which involved about 10 atoms.

Mass Dependence of Diffusion in a Supercooled Metallic Melt H.Ehmler, A.Heesemann, K.Rätzke, F.Faupel, U.Geyer: Physical Review Letters, 1998, 80[22], 4919-22

Table 23

Diffusivity of Co in Zr46.7Be27.5Ni10Ti8.3Cu7.5