Determination of Long-Range-Order Parameter of Fe 3 Si Alloy by means of 57 Fe Mössbauer Effect

A site population analysis of iron atoms in Fe3Si alloys with D03 superlattice structure was performed by 57Fe Mossbauer spectroscopy using crushed and annealed powder specimens with silicon concentrations of 23.3 and 25.5 at%. The Mossbauer spectra obtained were found to be superpositions of at least three six-line components. The relative intensity for each component has been analyzed using the thin foil approximation. The atomic configuration and the relative number of iron atoms of the component were determined from the values of the hyperfine field and the relative intensity for each component, and from these data the short-range-order parameter was determined. In order to determine the long-range-order parameters of the alloys, a two step procedure was used: First, the perfectly ordered D03 lattice of 25 at% Si was constructed by computer, and then atoms were replaced randomly so that any desired values of the alloy concentration and the degree of order are reached. By comparing the computer simulation with the result of the Mossbauer experiment, the long-rangeorder parameters, S(D03) and S(B2), were determined. The values agree well with those obtained by the powder X-ray diffraction technique. (Received June 12, 1985)