Electronic spin transitions in iron-bearing MgSiO3 perovskite

Stackhouse, Stephen; Brodholt, John P.; Price, G. D.

doi:10.1016/j.epsl.2006.10.035

Cited by 100 publications

(73 citation statements)

References 46 publications

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“…This conclusion is in agreement with results from experimental 6,8 and theoretical 4,5,7 studies. However, several publications 6,8,9 have suggested that the reduced volume of LS Fe 3þ B could lead to a redistribution of Fe 3þ from the A to the B site in the perovskite structure within the lower mantle.…”

Section: Resultssupporting

confidence: 92%

“…The A site is additionally occupied primarily by Mg 2þ and Fe 2þ , and the B site by Si 4þ and Al 3þ . Previous studies of spin transitions of Fe 3þ in FeAlPv are broadly consistent, and have shown that a high-spin (HS) (five unpaired d electrons) to low-spin (LS) (one unpaired d electron) transition is predicted when Fe 3þ occupies the B site, whereas Fe 3þ A (that is, Fe 3þ in the A site) is predicted to remain in the HS state at all pressures throughout the lower mantle [4][5][6][7][8][9] , and several studies have additionally predicted exchange of Fe 3þ from the A to the B site at pressures above the HS-LS transition 6,8,9 . The drop in electrical conductivity observed with increasing pressure [10][11][12] has generally been attributed to a HS-LS transition of Fe 3þ .…”

mentioning

confidence: 78%

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Effect of iron oxidation state on the electrical conductivity of the Earth’s lower mantle

et al. 2013

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Iron can adopt different spin states in the lower mantle. Previous studies indicate that the dominant lower-mantle phase, magnesium silicate perovskite (which contains at least half of its iron as Fe 3þ ), undergoes a Fe 3þ high-spin to low-spin transition that has been suggested to cause seismic velocity anomalies and a drop in laboratory-measured electrical conductivity. Here we apply a new synchrotron-based method of Mössbauer spectroscopy and show that Fe 3þ remains in the high-spin state in lower-mantle perovskite at conditions throughout the lower mantle. Electrical conductivity measurements show no conductivity drop in samples with high Fe 3þ , suggesting that the conductivity drop observed previously on samples with high Fe 2þ is due to a transition of Fe 2þ to the intermediate-spin state. Correlation of transport and elastic properties of lower-mantle perovskite with electromagnetic and seismic data may provide a new probe of heterogeneity in the lower mantle.

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Section: Resultssupporting

confidence: 92%

mentioning

confidence: 78%

Effect of iron oxidation state on the electrical conductivity of the Earth’s lower mantle

et al. 2013

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“…Although not able to capture all the possible correlated ground states, this corrective scheme has proved to be quite versatile in the description of the properties of several transition metal compounds 13,14 , minerals of the Earth's interior [13][14][15][16][17][18] , molecular complexes [19][20][21][22] , TMOs 10,11,23-25 , magnetic impurities and semiconductors 26 . Other corrective schemes have also been successfully used in the literature, including self-interaction corrected density functionals 27 , hybrid density functionals 28 , dynamical mean field theory 29 and reduced density matrix functional theory 30 .…”

Section: Dft+u Methodsmentioning

confidence: 99%

First-principles study of electronic and structural properties of CuO

2011

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We investigate the electronic and structural properties of CuO, which shows significant deviations from the trends obeyed by other transition-metal monoxides. Using an extended Hubbard-based corrective functional, we uncover an orbitally ordered insulating ground state for the cubic phase of this material, which was expected but never found before. This insulating state results from a fine balance between the tendency of Cu to complete its d-shell and Hund's rule magnetism. Starting from the ground state for the cubic phase, we also study tetragonal distortions of the unit cell (recently reported in experiments) and identify the equilibrium structure. Our calculations reveal an unexpected richness of possible magnetic and orbital orders, relatively close in energy to the ground state, whose stability depends on the sign and nature of distortion.

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“…Electronic spin-pairing transitions of Fe 2+ and/or Fe 3+ have been recently reported to occur in iron-bearing silicate perovskite using X-ray emission spectroscopy (XES) [6][7][8][9], Mössbauer spectroscopy [8][9][10][11] and theoretical calculations [12][13][14][15]. Though these transitions appear to be more complex than that in ferropericlase and are likely due to the low-symmetry oxygen ligand field in perovskite [16], the consensus on recent experimental results is that a high-spin to an intermediate-spin transition of Fe 2+ in perovskite occurs at the top of the lower mantle and the intermediate-spin Fe 2+ remains stable throughout the bulk of the lower mantle [9,11].…”

Section: Introductionmentioning

confidence: 99%

High-pressure X-ray diffraction and X-ray emission studies on iron-bearing silicate perovskite under high pressures

Lin

Speziale

Prakapenka

et al. 2010

High Pressure Research

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Iron-bearing silicate perovskite is believed to be the most abundant mineral of the Earth's lower mantle. Recent studies have shown that Fe 2+ exists predominantly in the intermediate-spin state with a total spin number of 1 in silicate perovskite in the lower part of the lower mantle. Here we have measured the spin states of iron and the pressure-volume relation in silicate perovskite [(Mg 0.6 ,Fe 0.4 )SiO 3 ] at pressure conditions relevant to the lowermost mantle using in situ X-ray emission and X-ray diffraction in a diamond cell. Our results showed that the intermediate-spin Fe 2+ is stable in the silicate perovskite up to ∼125 GPa but starts to transition to the low-spin state at approximately 135 GPa. Concurrent X-ray diffraction measurements showed a decrease of approximately 1% in the unit cell volume in the silicate perovskite [(Mg 0.6 ,Fe 0.4 )SiO 3 ], which is attributed to the intermediate-spin to the low-spin transition. The transition pressure coincides with the pressure conditions of the lowermost mantle, raising the possibility of the existence of the silicate perovskite phase with the low-spin Fe 2+ across the transition from the post-perovskite to the perovskite phases in the bottom of the D layer.

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Electronic spin transitions in iron-bearing MgSiO3 perovskite

Cited by 100 publications

References 46 publications

Effect of iron oxidation state on the electrical conductivity of the Earth’s lower mantle

Effect of iron oxidation state on the electrical conductivity of the Earth’s lower mantle

First-principles study of electronic and structural properties of CuO

High-pressure X-ray diffraction and X-ray emission studies on iron-bearing silicate perovskite under high pressures

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