Electrical transport, magnetism, and spin-state configurations of high-pressure phases of FeS

Abstract

Both the nature of the electrical transport and magnetism of high-pressure phases of FeS have been elucidated in relation to the spin-state configuration of Fe. This has been achieved by combined ${}^{57}\mathrm{Fe}$ M\"ossbauer spectroscopy and resistance measurements on samples pressurized in miniature gem-anvil pressure cells to \ensuremath{\sim}12 GPa in the range 300--5 K. Hexagonal FeS in the range 3--7 GPa exhibits magnetic nonmetallic behavior, whereas monoclinic FeS beyond \ensuremath{\sim}7 GPa is diamagnetic and nonmetallic. This is compelling experimental evidence to show that, along the room-temperature isotherm, hexagonal FeS has thermally activated charge carriers and a high-spin magnetic-electronic configuration, whereas monoclinic FeS adopts a magnetically quenched low-spin state and concomitant filled valence band.