期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：14
页码：5508-5512
DOI：10.1073/pnas.0808549106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Recent studies have shown that high pressure (P) induces the metallization of the Fe2+-O bonding, the destruction of magnetic ordering in Fe, and the high-spin (HS) to low-spin (LS) transition of Fe in silicate and oxide phases at the deep planetary interiors. Hematite (Fe2O3) is an important magnetic carrier mineral for deciphering planetary magnetism and a proxy for Fe in the planetary interiors. Here, we present synchrotron Mossbauer spectroscopy and X-ray diffraction combined with ab initio calculations for Fe2O3 revealing the destruction of magnetic ordering at the hematite [->] Rh2O3-II type (RhII) transition at 70 GPa and 300 K, and then the revival of magnetic ordering at the RhII [->] postperovskite (PPv) transition after laser heating at 73 GPa. At the latter transition, at least half of Fe3+ ions transform from LS to HS and Fe2O3 changes from a semiconductor to a metal. This result demonstrates that some magnetic carrier minerals may experience a complex sequence of magnetic ordering changes during impact rather than a monotonic demagnetization. Also local Fe enrichment at Earth's core-mantle boundary will lead to changes in the electronic structure and spin state of Fe in silicate PPv. If the ultra-low-velocity zones are composed of Fe-enriched silicate PPv and/or the basaltic materials are accumulated at the lowermost mantle, high electrical conductivity of these regions will play an important role for the electromagnetic coupling between the mantle and the core.
