Electronic and magnetic structures of the postperovskite-type Fe{sub 2}O{sub 3} and implications for planetary magnetic records and deep interiors.
Recent studies have shown that high pressure (P) induces the metallization of the Fe{sup 2+}-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 (Fe{sub 2}O{sub 3}) is an important magnetic carrier mineral for deciphering planetary magnetism and a proxy for Fe in the planetary interiors. Here, we present synchrotron Moessbauer spectroscopy and X-ray diffraction combined with ab initio calculations for Fe{sub 2}O{sub 3} revealing the destruction of magnetic ordering at the hematite {yields} Rh{sub 2}O{sub 3}-II type (RhII) transition at 70 GPa and 300 K, and then the revival of magnetic ordering at the RhII {yields} postperovskite (PPv) transition after laser heating at 73 GPa. At the latter transition, at least half of Fe{sup 3+} ions transform from LS to HS and Fe{sub 2}O{sub 3} 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.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Science Foundation (NSF)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 951902
- Report Number(s):
- ANL/XSD/JA-64151; PNASA6; TRN: US0902339
- Journal Information:
- Proc. Natl. Acad. Sci. USA, Vol. 106, Issue 14 ; Apr. 7, 2009; ISSN 0027-8424
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
High-pressure crystal structure and equation of state of ferromagnesian jeffbenite: implications for stability in the transition zone and uppermost lower mantle
Mineralogical effects on the detectability of the postperovskite boundary