High-pressure metallization and electronic-magnetic propertiesof hexagonal cubanite (CuFe2S3) |
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Authors: | G K Rozenberg M P Pasternak G R Hearne C A McCammon |
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Institution: | School of Physics and Astronomy, Tel-Aviv University, Ramat-Aviv 69978, Israel, IL Department of Physics, University of the Witwatersrand,P O Wits 2050, Johannesburg-Gauteng, South Africa, ZA Bayerisches Geoinstitut, Universit?t Bayreuth,W-95440 Bayreuth, Germany, DE
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Abstract: | ?57Fe Mössbauer studies at room temperature and temperature-dependent resistance studies have been performed on a natural specimen of cubanite (CuFe2S3) in a diamond-anvil cell at pressures up to ~10 GPa. An insulator-metal phase transition occurs in the range 3.4–5.8 GPa coinciding with a previously observed structural transition from an orthorhombic to a hexagonal NiAs (B8) structure. The room temperature data shows that the metallization process concurs with a gradual transition from a magnetically ordered phase at low pressure to a nonmagnetic or paramagnetic phase at high-pressure. The change in magnetic behaviour at the structural transition may be attributed to a reduction of the Fe-S-Fe superexchange angle formed by edge-sharing octahedra occurring in the high-pressure phase. The non-magnetic or paramagnetic metallic phase at high pressure is retained upon decompression to ambient pressure-temperature conditions, indicative of substantial hysteresis associated with the pressure driven orthorhombic→hexagonal structural transition. The pressure evolution of both the 57Fe Mössbauer hyperfine interaction parameters and resistance behaviour is consistent with the transition from mixed-valence character in the low pressure orthorhombic structure to that of extended-electron delocalization in the hexagonal phase at high-pressure. |
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