We have synthesized the hexagonal pyrrhotite nanodisks with the NiAs-type structure via thermal decomposition of ferrous chloride and thiourea in oleylamine. Mössbauer spectra analysis shows that the main part of iron of hexagonal pyrrhotite is in the valence state, and the spectrum has broadened half-maximum width due to the vacancy distribution. Magnetic measurements indicate that the magnetic moment configuration of nanodisks transforms from the ferrimagnetic to the ferromagnetic state at 400 K and magnetic moment disordering takes place at the Curie temperature, 580 K, at which ferromagnetic state transforms to paramagnetic structure. This magnetic transition behavior can be explained in terms of the iron vacancy rearrangement.
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