The diffusion of Fe in DO3 ordered Fe76Si24 was studied under hydrostatic pressures at 934K. The diffusion coefficients were determined by using a radiotracer technique which involved using implanted 59Fe and serial sectioning by precision grinding. It was deduced that the activation volume for diffusion was 1.48 x 10-21m3 (1.27 atomic volumes). This large value was attributed to vacancy-mediated Fe diffusion, in which di-vacancies or larger vacancy clusters were probably involved. This suggestion was supported by positron annihilation experiments, which revealed a marked increase in the lifetime of trapped positrons in Fe75Si25 at higher temperatures.

A.Gude, K.Freitag, B.Sepiol, G.Vogl, H.Mehrer: Physica Status Solidi B, 1996, 197[2], 299-307