Structural, magnetic properties, and electronic structure of hexagonal FeCoSn compound

The structural, magnetic properties, and electronic structures of hexagonal FeCoSn compounds with as-annealed bulk and ribbon states were investigated by x-ray powder diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscope (TEM), scanning electron microscope (SEM), magnetic measurements, and first-principles calculations. Results indicate that both states of FeCoSn show an Ni₂In-type hexagonal structure with a small amount of FeCo-rich secondary phase. The Curie temperatures are located at 257 K and 229 K, respectively. The corresponding magnetizations are 2.57 μ_B/f.u. and 2.94 μ_B/f.u. at 5 K with a field of 50 kOe (1 Oe=79.5775 A·m^-1). The orbital hybridizations between 3d elements are analyzed from the distribution of density of states (DOS), showing that Fe atoms carry the main magnetic moments and determine the electronic structure around Fermi level. A peak of DOS at Fermi level accounts for the presence of the FeCo-rich secondary phase. The Ni₂In-type hexagonal FeCoSn compound can be used during the isostructural alloying for tuning phase transitions.