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Spin-state Crossover and Hyperfine Interactions of Iron in MgSiO 3 Perovskite

Spin-state Crossover and Hyperfine Interactions of Iron in MgSiO 3 Perovskite. Han Hsu ( 徐翰 ) Department of Chemical Engineering & Materials Science Materials Research Science & Engineering Center (MRSEC) University of Minnesota. UMN MRSEC. Iron in lower-mantle minerals.

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Spin-state Crossover and Hyperfine Interactions of Iron in MgSiO 3 Perovskite

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  1. Spin-state Crossover and Hyperfine Interactions of Iron in MgSiO3 Perovskite Han Hsu (徐翰) Department ofChemical Engineering & Materials Science Materials Research Science & Engineering Center (MRSEC) University of Minnesota UMN MRSEC

  2. Iron in lower-mantle minerals Iron-bearing MgSiO3 Pv (Mg,Fe)O ferropericlase + Ferropericlase ~ 20 vol% Perovskite ~ 75 vol% Depth: 660 – 2890 km Pressure: 23 - 135 GPa Temperature: 1900 – 4000 K

  3. Spin states of Fe2+ and Fe3+ High spin Low spin Intermediate spin ?????????? EC Fe2+ S = 0 S = 2 S = 1 EC Fe3+ S = 3/2 S = 5/2 S = 1/2 Compression

  4. Spin matters! Crowhurst et al., Science (2008) Wentzcovitch et al., PNAS USA (2009) A HS-LS crossover in (Mg,Fe)O directly affects its structural, elastic, optical and conducting properties. T. Tsuchiya et al, PRL (2006) J. Crowhurst et al., Science (2008) A. F. Goncharov et al., Science (2006) J.-F. Lin et al., GRL (2007) R. M. Wentzcovitch et al., PNAS (2009) Z. Wu et al., PRB (2009) and many more… K (GPa)

  5. Iron-bearing MgSiO3(Pbnm) Fe2+ (Mg,Fe)SiO3 Fe3+ (Mg,Fe)(Si,Fe)O3 • Most abundant mineral (~ 75 vol%), with ~ 10% Fe. • Fe3+/Fe2+ not well characterized (Fe3+/∑Fe = 0.3-0.6) • Controversial spin-state crossover

  6. XES and Mössbauer spectra Badro et al., Science (2004) McCammon et al., Nature Geosci. (2008) Catalli et al., EPSL (2010)

  7. QS of Fe in MgSiO3 Pv (Mg,Fe)SiO3 (Mg,Fe)(Si,Fe)O3 Exp McCammon et al., Nature Geosci. (2008);Jackson et al., Am. Mineral. (2005); Catalli et al., EPSL (2010). Hsu et al., PRL (2011)

  8. (Mg,Fe)SiO3 High-QS Low-QS 24 GPa Spin-down nx2-y2 = 0.45 nxy = 0.60 15 GPa Spin-down nyz = 0.97 Hsu et al., EPSL (2010)

  9. (Mg,Fe)(Si,Fe)O3 Self-consistent USC (eV) Hsu et al., PRL (2011)

  10. Anomaly in (Mg,Fe)(Si,Fe)O3 Hsu et al., PRL (2011)

  11. Iron-bearing MgSiO3 Pv • Ferrous iron in (Mg,Fe)SiO3 • - HS in the lower-mantle pressure range (23-135 GPa) • - At ~30 GPa, a crossover from QS = 2.4 to 3.5 mm/s • - Neither HS-LS nor HS-IS crossover • Ferric iron in (Mg,Fe)(Si,Fe)O3 • - A-site iron remains in HS state in 23-135 GPa. • - B-site iron undergoes a HS-LS crossover in 45-60 GPa. • - B-site HS-LS crossover may lead to seismic anomalies.

  12. Thank you!!! Physics Today May 2011 (pp. 12) Physical Review Letters Vol. 106 Iss. 11

  13. Future work Fe-bearing MgSiO3 post perovskite Fe with QS= 4.0 mm/s IS state? Lin et al., Nature (2008)

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