Evidence of Defect-Mediated Zirconium Self-Diffusion in AmorphousCo92Zr8

We have measured the pressure dependence of ${}^{95}\mathrm{Zr}$ self-diffusion in structurally relaxed ${\mathrm{Co}}_{92}{\mathrm{Zr}}_8$ glass at 698 K. The resulting activation volume of $(0.9\pm 0.1)\Omega$, where $\Omega$ is the mean atomic volume, is similar to vacancy diffusion in crystalline solids. This suggests that, while Co does not diffuse via thermal defects in Co-rich Co-Zr glasses [P. Klugkist et al., Phys. Rev. Lett. 80, 3288 (1998)], Zr self-diffusion is mediated by vacancylike defects. We thus provide evidence of the existence of an opposite Kirkendall effect in interdiffusion between certain amorphous alloys as proposed by K. N. Tu and T. C. Chou [Phys. Rev. Lett. 61, 1863 (1988)].