The effect of pressure on the electronic states of FeS and studied by Mössbauer spectroscopy

Abstract

We have measured under pressure Mössbauer spectra of FeS and 3c-type up to 16 GPa and x-ray diffraction patterns of up to 11 GPa at room temperature. It is found for that the compressibilities of the lattice parameters exhibit definite anomalies at around 4.5 GPa and that there is no change in the crystal structure up to 11 GPa. Magnetically ordered Mössbauer spectra are observed below 6.5 GPa for FeS and 4.5 GPa for , whereas the spectra above these pressures are typical of a paramagnetic ordering with a quadrupole splitting. A large reduction in the centre shift is observed at these pressures. It is found that there is a distinct steplike feature of the magnetic hyperfine field at 3.5 GPa for FeS. The electronic states of FeS and are deduced from the volume dependences of the centre shift and the magnetic hyperfine field. Below 3.5 GPa for FeS, the electronic state has an insulating character and the electrons on the iron are well localized and thus contribute to the magnetic moment. In the intermediate-pressure range, from 3.5 to 6.5 GPa for FeS and below 4.5 GPa for , the electronic state is like a semimetallic one. Above 6.5 GPa for FeS and 4.5 GPa for , the electronic bandwidth is large enough to cause the state to become metallic and produces a collapse of the iron magnetic moment.