The Electrical Conductivity of Post-Perovskite in Earth's D'' Layer
Kenji Ohta,1
Suzue Onoda,2
Kei Hirose,1,3*
Ryosuke Sinmyo,1
Katsuya Shimizu,2
Nagayoshi Sata,3
Yasuo Ohishi,4
Akira Yasuhara5
Recent discovery of a phase transition from perovskite to post-perovskite suggests that the physical properties of Earth's lowermost mantle, called the D'' layer, may be different from those of the overlying mantle. We report that the electrical conductivity of (Mg0.9Fe0.1)SiO3 post-perovskite is >102 siemens per meter and does not vary greatly with temperature at the conditions of the D'' layer. A post-perovskite layer above the core-mantle boundary would, by electromagnetic coupling, enhance the exchange of angular momentum between the fluid core and the solid mantle, which can explain the observed changes in the length of a day on decadal time scales. Heterogeneity in the conductivity of the lowermost mantle is likely to depend on changes in chemistry of the boundary region, not fluctuations in temperature.
1 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan.
2 Center for Quantum Science and Technology under Extreme Conditions, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
3 Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan.
4 Japan Synchrotron Radiation Research Institute, 1-1-1 Koto, Sayo, Hyogo 679-5198, Japan.
5 JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.
* To whom correspondence should be addressed. E-mail: kei{at}geo.titech.ac.jp (K.H.)
