The available experimental data on the diffusion of this element in body-centered cubic Fe were analyzed by using a model which took account of the effect of magnetic transitions in the  phase. It was found that the diffusion of C in this phase could be described by:

D (m2/s) = 2.72 x 10-7exp[-59.6(kJ/mol)(1+0.337s2)/RT]

where s was the ratio of the spontaneous magnetization in Fe, at a given temperature, to that at 0K. In the case of C diffusion in -Fe, the increase in activation energy due to magnetic spin ordering was 20kJ/mol.

Y.Iijima: Journal of Alloys and Compounds, 1996, 234[2], 290-4