DFT and Mössbauer Spectroscopy Study of a FeTe0.5Se0.5 Single Crystal

The iron based superconductor FeSe0.5Te0.5 has been studied applying Mössbauer spectroscopy and ab initio density functional theory calculations of hyperfine parameters of iron nuclei. It has been shown that the presence of interstitial iron atoms leads to dividing of iron atoms in the compound into three groups with different hyperfine parameters. The experimental room-temperature Mössbauer spectrum has been well described within a three-group model, based on the results of ab initio calculations. The low-temperature Mössbauer spectrum has been described by a set of magnetic sextets, characterized by a distribution of hyperfine fields on 57Fe nuclei. The latter is compatible with an incommensurate spin-density wave phase, which coexists with superconductivity as it was observed also in other iron-based superconductors.