Thermal vacancy formation was studied for the Heusler-type ferromagnetic alloys Co2MnZ (Z = Si, Ge, Sn) as a function of temperature (773–1273K) by the density, electrical resistivity and positron annihilation measurements. The vacancy concentration increased with increase in quenching temperature and particularly, a high vacancy concentration exceeding 2% was observed in Co2MnGe and Co2MnSn. Estimated vacancy formation and migration energies were comparable with those for B2-type FeAl and CoGa alloys with high vacancy concentration. Further, the vacancy type and the vacancy site were examined for alloys quenched from 773K. As a result, it was suggested that the mono-vacancies were randomly distributed over the lattice sites.

Thermal Vacancy Formation in Co-Based Heusler-Type Alloys Co2MnZ (Z = Si, Ge, Sn). M.Kogachi, S.Kikuchi, T.Fujiwara, F.Hori: Journal of Alloys and Compounds, 2009, 480[2], 462-8