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

Both the nature of the electrical transport and magnetism of high-pressure phases of FeS have been elucidated in relation to the spin-state configurat ion of Fe. This has been achieved by combined Fe-57 Mossbauer spectroscopy and resistance measurements on samples pressurized in miniature gem-anvil p ressure cells to similar to 12 GPa in the range 300-5 K. Hexagonal FeS in t he range 3-7 GPa exhibits magnetic nonmetallic behavior, whereas monoclinic FeS beyond similar to 7 GPa is diamagnetic and nonmetallic. This is compel ling experimental evidence to show that, along the room-temperature isother m, hexagonal FeS has thermally activated charge carriers and a high-spin ma gnetic-electronic configuration, whereas monoclinic FeS adopts a magnetical ly quenched low-spin state and concomitant filled valence band. [S0163-1829 (99)01633-1].