Pressure dependence ofCo60diffusion in amorphousCo76.7Fe2Nb14.3B7

The pressure dependence of ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$ diffusion has been measured in melt-spun amorphous ${\mathrm{Co}}_{76.7}$ ${\mathrm{Fe}}_2$ ${\mathrm{Nb}}_{14.3}$ ${\mathrm{B}}_7$ and fcc Co, and the temperature dependence and the relaxation behavior were investigated in the metallic glass. A radio-tracer technique in conjunction with ion-beam sputtering for serial sectioning was employed. The samples were characterized by means of differential scanning calorimetry, electron microprobe analysis, and x-ray diffraction prior to and after the diffusion anneals. Within the experimental error margins, no pressure dependence was observed in amorphous ${\mathrm{Co}}_{76.7}$ ${\mathrm{Fe}}_2$ ${\mathrm{Nb}}_{14.3}$ ${\mathrm{B}}_7$. The activation volume was found to be V=-(0.06±0.1)Ω, where Ω is the atomic volume of Co. This result shows that diffusion in the metallic glass is not mediated through quasivacancies in thermal equilibrium.