The formation of thermal vacancies was studied, up to the ferromagnetic-paramagnetic phase transition, by means of positron lifetime spectroscopy. Low values of the vacancy formation enthalpies in the ferromagnetic (0.77eV) and paramagnetic (0.74eV) states were found in the case of stoichiometric Fe75Si25. These values increased substantially to 1.11eV and 1.07eV, respectively, in the case of Fe-rich Fe79Si21. Also, an upper limit on the vacancy migration enthalpy was deduced after rapid temperature changes. The results were explained with regard to recent tracer diffusion data.

Thermal Formation of Vacancies in Fe3Si. E.A.Kümmerle, K.Badura, B.Sepiol, H.Mehrer, H.E.Schaefer: Physical Review B, 1995, 52[10], R6947-50