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}$${\mathrm{B}}_7$ and in fcc Co. Within experimental accuracy no pressure dependence and an isotope effect E=(${\mathit{D}}_{\mathrm{\alpha }}$/${\mathit{D}}_{\mathrm{\beta }}$-1)/[(${\mathit{m}}_{\mathrm{\beta }}$/${\mathit{m}}_{\mathrm{\alpha }}$${)}^{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.

• Received 2 July 1990

DOI:https://doi.org/10.1103/PhysRevLett.65.1219