Chalcogenides and Pnictides
Iron chalcogenides and pnictides reveal a rich variety of magnetic properties as well as high-temperature superconductivity. Mössbauer spectroscopy is particularly well suited to characterize their magnetic state. For instance, Mössbauer spectra of the intercalated sulfide Fe1/3TaS2 (Figure below, left) reflect the transition of the Fe2+ ions from a paramagnetic to a ferromagnetic state below TC ~ 40 K, where the magnetic moments are aligned along the c direction of the hexagonal crystal structure. On the other hand, the host-guest-type selenide [Cs6Cl[Fe24Se26] exhibits a complex hyperfine pattern indcating a non-collinear spin structure. The pressure dependence of the magnetic properties was studied by synchrotron Mössbauer source (SMS) spectroscopy (Figure below, right) and it was demonstrated that the complex hyperfine pattern is suppressed above 10 GPa. In the same pressure range the electrical resistivity is strongly reduced which indicates that the electronic system becomes more itinerant.