Electronic spin and valence states of Fe in CaIrO{sub 3} - type silicate post-perovskite in the earth's lowestmost mantle.
The electronic spin and valence states of Fe in post-perovskite ((Mg{sub 0.75}Fe{sub 0.25})SiO{sub 3}) have been investigated by synchrotron X-ray diffraction, Moessbauer and X-ray emission spectroscopy at 142 GPa and 300 K. Rietveld refinement of the X-ray diffraction patterns revealed that our sample was dominated by CaIrO{sub 3}-type post-perovskite. Combined Moessbauer and X-ray emission results show that Fe in post-perovskite is predominantly Fe{sup 2+} (70%) in the intermediate-spin state with extremely high quadrupole splitting of 3.77(25) mm/s. The remaining 30% Fe can be assigned to two sites. Compared with recent studies, our results indicate that the intermediate-spin Fe{sup 2+} is stabilized in CaIrO{sub 3}-type post-perovskite over a wide range of Fe content, whereas the low-spin Fe{sup 3+} is more dominant in the 2 x 1 kinked post-perovskite structure. The characterization of these structural and compositional effects on the spin and valence states of Fe in post-perovskite can help in understanding the geochemical and geophysical behavior of the core-mantle region.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC; NSF; NNSA; Thomas and Ray Burke Student Job Program
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1005158
- Report Number(s):
- ANL/XSD/JA-69210
- Journal Information:
- Geophys. Res. Lett., Journal Name: Geophys. Res. Lett. Journal Issue: Nov. 19, 2010 Vol. 37; ISSN 0094-8276
- Country of Publication:
- United States
- Language:
- ENGLISH
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