Polycrystalline samples of FeSe 0.82 and FeSe 0.5Te 0.5 were synthesized using a solid-state reaction route. Bulk superconductivity was confirmed using SQUID magnetometry. The onset of T c was at 8.0 K for FeSe 0.82 and 12.5 K for FeSe 0.5Te 0.5. Paramagnetic 57Fe Mössbauer spectra were recorded at temperatures between 5.4 and 320 K in transmission geometry. All spectra exhibited simple quadrupole splitting. For FeSe 0.5Te 0.5 a small drop in the quadrupole splitting was observed about T c upon cooling. Additionally, for both samples the isomer shift and the total absorption started to drop around T c, indicating a softening of the lattice. The drop is estimated to correspond to at least 60 K from the original Debye temperatures.
- Fe Mössbauer spectroscopy
- Chalcogenide superconductivity
- Iron-based superconductors