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A local model based on the idea of atoms distributed within a crystalline lattice and following a binomial probability method for describing the hyperfine field distributions obtained from the room temperature Mössbauer spectra of the disordered Fe–Ni system is presented. This model allows one to calculate the mean hyperfine field for each concentration from 5 to 95 at. % Ni, to determine what are the most probable sites and to interpret why the mean hyperfine field initially increases and then decreases with the Ni concentration in the BCC phase. The results are in good agreement with the experimental results except for Invar composition and for 85 at. % Ni which demand a different treatment.

The extended x-ray absorption fine structure (EXAFS) recorded from tin-doped α-Fe2O3, prepared by the mechanical milling of tin dioxide and α-Fe2O3 and by the hydrothermal processing of iron- and tin-containing precipitates, can be interpreted in terms of a model in which tin occupies both substitutional octahedral sites and the interstitial octahedral sites in the corundum-related α-Fe2O3 structure. The EXAFS and 119Sn Mössbauer spectra suggest that structural models derived from x-ray powder diffraction data do not adequately describe the complexity of the local environment of tin in α-Fe2O3. In particular, the EXAFS and 119Sn Mössbauer spectra recorded from materials made by mechanical milling show evidence of more disorder. The 119Sn Mössbauer spectra also indicate that the degree of order in the materials made by both methods is far from perfect and that the microstructural defects are highly sensitive to tin content and the preparative method.

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