Site-Selective Magnetic Moment Collapse in Compressed Fe_5O_6

Iron oxide is one of the most important components in the Earth's mantle. The recent discovery of the stable presence of Fe_5O_6 in the Earth's mantle environment has stimulated significant interests in understanding of this new category of iron oxides. We report the electronic structure and magnetic properties of Fe_5O_6 calculated by the density functional theory plus dynamic mean field theory (DFT + DMFT) approach. Our calculations indicate that Fe_5O_6 is a conductor at ambient pressure with dominant Fe-3d density of states at the Fermi level. The magnetic moments of iron atoms at three non-equivalent crystallographic sites in Fe_5O_6 collapse at significantly different rates under pressure. This site-selective collapse of magnetic moments originates from the shifting of energy levels and the consequent charge transfer among the Fe-3d orbits when Fe_5O_6 is being compressed. Our simulations suggest that there could be high conductivity and volume contraction in Fe_5O_6 at high pressure, which may induce anomalous features in seismic velocity, energy exchange, and mass distribution in the deep interior of the Earth.