It is established by Mossbauer spectroscopy investigation that the Nee
l temperatures and superfine magnetic fields un Sn-119 nuclei in Mn19.
5-xFe0.5Snx alloys isotypical to the beta-Mn structure arise due to th
e concentration expansion of the crystal lattice and interatomic excha
nge interactions of the four types: Sn - Mn, Sn - Fe, Sn - Sn, and Mn
- Fe.