Characterization of FeOOH polymorphs and ferrihydrite using low-temperature, applied-field, Mössbauer spectroscopy

Mössbauer spectroscopy obtained with the sample at low temperatures and subject to large magnetic fields is discussed in terms of its use in analysing the naturally occurring polymorphs of FeOOH and the common growth precursor, ferrihydrite. Experiments on well-characterized synthetic samples provided benchmark results. A relatively simple means of quantitative analysis was used, in which sextets of Voigtian-shaped lines were summed and least-squares fitted. The results are discussed in terms of the magnetic structures of each compound.