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The effect of iron spin transition on electrical conductivity of (Mg,Fe)O magnesiowüstite.

Ohta K, Hirose K, Onoda S, Shimizu K - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2007)

Bottom Line: The results demonstrate that the electrical conductivity increases with increasing pressure to about 60 GPa and exhibits anomalous behavior at higher pressures; it conversely decreases to around 80 GPa and again increases very mildly with pressure.A very small pressure effect on the electrical conductivity above 80 GPa suggests that a dominant conduction mechanism changes by this electronic spin transition.The electrical conductivity below 2000-km depth in the mantle may be much smaller than previously thought, since the spin transition takes place also in (Mg,Fe)SiO3 perovskite.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan .

ABSTRACT
We measured the electrical conductivity of Mg0.81Fe0.19O magnesiowüstite, one of the important minerals comprising Earth's lower mantle, at high pressures up to 135 GPa and 300 K in a diamond-anvil cell (DAC). The results demonstrate that the electrical conductivity increases with increasing pressure to about 60 GPa and exhibits anomalous behavior at higher pressures; it conversely decreases to around 80 GPa and again increases very mildly with pressure. These observed changes may be explained by the high-spin to low-spin transition of iron in magnesiowüstite that was previously reported to occur in a similar pressure range. A very small pressure effect on the electrical conductivity above 80 GPa suggests that a dominant conduction mechanism changes by this electronic spin transition. The electrical conductivity below 2000-km depth in the mantle may be much smaller than previously thought, since the spin transition takes place also in (Mg,Fe)SiO3 perovskite.

No MeSH data available.


Electrical conductivity (σ) of magnesiowüstite at 300 K as a function of pressure. Filled symbols, present study; open symbols, Li and Jeanloz [1990] and Dobson and Brodholt [2000].
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f3-83_097: Electrical conductivity (σ) of magnesiowüstite at 300 K as a function of pressure. Filled symbols, present study; open symbols, Li and Jeanloz [1990] and Dobson and Brodholt [2000].

Mentions: We conducted three separate sets of experiments. The position and shape of the electrodes on the sample did not change during compression above 20–30 GPa in each run. The resistance of electrodes was checked before measuring the sample resistance at each pressure. In the first run, the sample resistance was measured during both compression and decompression (Fig. 2). On compression, it decreased from 530 MΩ at 12 GPa to 98 MΩ at 55 GPa, and then conversely increased with pressure to 470 MΩ at 80 GPa. We also observed similar change in the resistance during decompression to 23 GPa. The estimated electrical conductivity is shown in Fig. 3.


The effect of iron spin transition on electrical conductivity of (Mg,Fe)O magnesiowüstite.

Ohta K, Hirose K, Onoda S, Shimizu K - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2007)

Electrical conductivity (σ) of magnesiowüstite at 300 K as a function of pressure. Filled symbols, present study; open symbols, Li and Jeanloz [1990] and Dobson and Brodholt [2000].
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756880&req=5

f3-83_097: Electrical conductivity (σ) of magnesiowüstite at 300 K as a function of pressure. Filled symbols, present study; open symbols, Li and Jeanloz [1990] and Dobson and Brodholt [2000].
Mentions: We conducted three separate sets of experiments. The position and shape of the electrodes on the sample did not change during compression above 20–30 GPa in each run. The resistance of electrodes was checked before measuring the sample resistance at each pressure. In the first run, the sample resistance was measured during both compression and decompression (Fig. 2). On compression, it decreased from 530 MΩ at 12 GPa to 98 MΩ at 55 GPa, and then conversely increased with pressure to 470 MΩ at 80 GPa. We also observed similar change in the resistance during decompression to 23 GPa. The estimated electrical conductivity is shown in Fig. 3.

Bottom Line: The results demonstrate that the electrical conductivity increases with increasing pressure to about 60 GPa and exhibits anomalous behavior at higher pressures; it conversely decreases to around 80 GPa and again increases very mildly with pressure.A very small pressure effect on the electrical conductivity above 80 GPa suggests that a dominant conduction mechanism changes by this electronic spin transition.The electrical conductivity below 2000-km depth in the mantle may be much smaller than previously thought, since the spin transition takes place also in (Mg,Fe)SiO3 perovskite.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan .

ABSTRACT
We measured the electrical conductivity of Mg0.81Fe0.19O magnesiowüstite, one of the important minerals comprising Earth's lower mantle, at high pressures up to 135 GPa and 300 K in a diamond-anvil cell (DAC). The results demonstrate that the electrical conductivity increases with increasing pressure to about 60 GPa and exhibits anomalous behavior at higher pressures; it conversely decreases to around 80 GPa and again increases very mildly with pressure. These observed changes may be explained by the high-spin to low-spin transition of iron in magnesiowüstite that was previously reported to occur in a similar pressure range. A very small pressure effect on the electrical conductivity above 80 GPa suggests that a dominant conduction mechanism changes by this electronic spin transition. The electrical conductivity below 2000-km depth in the mantle may be much smaller than previously thought, since the spin transition takes place also in (Mg,Fe)SiO3 perovskite.

No MeSH data available.