Microwave Investigation of Greigite Nanoparticles Magnetic Properties

We experimentally investigated the nanoparticles of iron sulfide Fe
₃
S
₄
, known as the mineral greigite, with the mean crystallite size of ~30 and ~120 nm, which have been prepared via hydrothermal synthesis by using two different surfactants (oleic acid and cetyltrimethylammonium bromide). Their crystallinity and phase purity are probed by X-ray diffraction. For detailed characterization of the ferrimagnetic state and its temperature evolution, the SQUID magnetometry, ferromagnetic resonance is used. Moreover, special attention is given to anomalies that remind the spin re-orientation and Verwey transitions in isostructural iron oxide Fe
₃
O
₄
, magnetite.