Magnetic, FMR and mössbauer studies of nanocrystalline greigite

Abstract Iron sulphide Fe3S4, known as the mineral greigite, has been prepared in two distinct nanocrystalline forms with the mean crystallite size of dXRD ≈ 30 and 80 nm via hydrothermal synthesis by using two different surfactants (oleic acid and cetyltrimethylammonium bromide). Their crystallinity and phase purity are probed by X-ray diffraction and Mossbauer spectroscopy. For detailed characterization of the ferrimagnetic state and its temperature evolution, the SQUID magnetometry, ferromagnetic resonance and the temperature dependence of 57Fe Mossbauer spectra are used. The blocking behaviour of the nanocrystalline samples is discussed with respect to magnetic and Mossbauer data. Moreover, special attention is given to the analysis of temperature-dependent data, which reveals that: first, spin reorientation associated with the change in easy axis from " open=" 110 to " open=" 111 on cooling occurs at ≈100 K, secondly, Verwey-like transition is not present.