Spin-state Crossover and Hyperfine Interactions of Iron in

Spin-state Crossover and Hyperfine Interactions of Iron in Mg. Si. O 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 Ferropericlase ~ 20 vol% Iron-bearing Mg. Si. O 3 Pv (Mg, Fe)O ferropericlase Perovskite ~ 75 vol% + Depth: 660 – 2890 km Pressure: 23 - 135 GPa Temperature: 1900 – 4000 K

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

Spin matters! K (GPa) 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… Crowhurst et al. , Science (2008) Wentzcovitch et al. , PNAS USA (2009)

Iron-bearing Mg. Si. O 3 (Pbnm) Fe 2+ (Mg, Fe)Si. O 3 Fe 3+ (Mg, Fe)(Si, Fe)O 3 • Most abundant mineral (~ 75 vol%), with ~ 10% Fe. • Fe 3+/Fe 2+ not well characterized (Fe 3+/∑Fe = 0. 3 -0. 6) • Controversial spin-state crossover

XES and Mössbauer spectra Badro et al. , Science (2004) Mc. Cammon et al. , Nature Geosci. (2008) Catalli et al. , EPSL

QS of Fe in Mg. Si. O 3 Pv (Mg, Fe)Si. O 3 Exp Mc. Cammon et al. , Nature Geosci. (2008); Jackson et al. , Am. Mineral. (2005); Catalli et al. , EPSL (2010). (Mg, Fe)(Si, Fe)O 3 Hsu et al. , PRL

(Mg, Fe)Si. O 3 High-QS Low-QS 24 GPa 15 GPa Spin-down nx 2 -y 2 = 0. 45 nxy = 0. 60 Spin-down nyz = 0. 97 Hsu et al. , EPSL (2010)

(Mg, Fe)(Si, Fe)O 3 Self-consistent USC (e. V) Hsu et al. , PRL (2011)

Anomaly in (Mg, Fe)(Si, Fe)O 3 Hsu et al. , PRL (2011)

Iron-bearing Mg. Si. O 3 Pv • Ferrous iron in (Mg, Fe)Si. O 3 - 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)O 3 - 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.

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

Future work Fe-bearing Mg. Si. O 3 post perovskite Fe with QS= 4. 0 mm/s IS state? Lin et al. , Nature (2008)