Site occupation and local hyperfine fields in σ Fe-Cr alloys

High field 57Fe Moessbauer and neutron diffraction measurements were performed for a series of σ-Fe x Cr1-x samples covering the full concentration range (0.50≤x≤0.55) of phase formation. Occupation numbers for the individual lattice sites, obtained from the neutron diffraction data, are used to determine the local hyperfine parameters by a new analysis procedure, which simultaneously fits all measured Moessbauer spectra, thus allowing a drastic reduction of the number of free parameters