The migration of 14C at 976 to 1673K was determined by using the residual activity method. It was found that, at temperatures above the Curie point (1396K), the Arrhenius plot was linear. Deviations at lower temperatures were attributed to the effect of magnetic spin ordering. The diffusivity across the Curie point could be described by:

D (m2/s) = 7.6 x 10-6exp[-140(kJ/mol)(1 + 0.109s2)/RT]

where s was the ratio of the spontaneous magnetization, at a given temperature, to that at 0K.

Y.Iijima, F.Makuta, R.P.Agarwala, K.Hirano: Materials Transactions, 1989, 30[12], 984-90