The influence of aluminium substitution and crystallinity on the Mössbauer spectra of goethite

Both aluminium substitution and poor crystallinity reduce the magnetic hyperfine field of goethite. Mössbauer spectra taken at 4·2 K show that the effect of poor crystallinity is similar to that of Al substitution, i.e. it reduces the saturation hyperfine field. A multiple correlation was found to exist between the magnetic hyperfine field at 4·2 K as a dependent variable vs Al substitution and crystallinity as independent variables. If a hyperfine field is to be interpreted with respect to either Al substitution or crystallinity, it is therefore necessary to have knowledge of the other variable.