In this article, x-ray photoelectron spectroscopy (XPS) spectra of iron chalcogenides, FeS, Fe7S8, and Fe7Se8 are presented. FeS (troilite) and Fe7S8 (pyrrhotite) are among the most common iron compounds on earth. FeS is antiferromagnetic below the Néel temperature of TN=593-598 K. Above Tα=420 K, FeS is a metal with an NiAs-type crystal structure, but becomes an insulator with a narrow band gap of 0.04 eV below Tα. This transition known as the α-transition is accompanied by a small displacement of the Fe and S atoms from the regular NiAs-type structure. Fe7S8 and Fe7Se8 are ferrimagnetic metals with Néel temperatures of TN=578 and 423-460 K, respectively. The crystal structures of Fe7S8 and Fe7Se8 are derived from the NiAs-type one by introducing ordered Fe vacancies. The polycrystalline samples were synthesized by the Bridgman method. Clean surfaces were obtained by scraping in situ with a diamond file. All the XPS spectra of the iron chalcogenides are taken at room temperature.
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