Pressure dependence and isotope effect of self-diffusion in a metallic glass

Abstract

The pressure dependence and isotope effect of cobalt diffusion have been measured in amorphous ${\mathrm{Co}}_{76.7}$${\mathrm{Fe}}_{2}$${\mathrm{Nb}}_{14.3}$${\mathrm{B}}_{7}$ and in fcc Co. Within experimental accuracy no pressure dependence and an isotope effect E=(${\mathit{D}}_{\mathrm{\ensuremath{\alpha}}}$/${\mathit{D}}_{\mathrm{\ensuremath{\beta}}}$-1)/[(${\mathit{m}}_{\mathrm{\ensuremath{\beta}}}$/${\mathit{m}}_{\mathrm{\ensuremath{\alpha}}}$${)}^{1/2}$-1]=0.1 were found in ${\mathrm{Co}}_{76.7}$${\mathrm{Fe}}_{2}$${\mathrm{Nb}}_{14.3}$${\mathrm{B}}_{7}$. These results show that diffusion in the metallic glass is not mediated through quasivacancies in thermal equilibrium similar to crystalline Co. Diffusion rather occurs via a direct mechanism involving about ten atomic masses.