The electrical resistance measurements of (Mg,Fe)SiO3 perovskite at high pressures and implications for electronic spin transition of iron

We have measured the electrical resistance of (Mg0.9Fe0.1)SiO3 perovskite with increasing pressure in a diamond-anvil cell (DAC). Results demonstrate that the electrical conductivity increased with pressure to about 70 GPa, then conversely decreased to around 85 GPa, and again increased mildly to 135 GPa. As inferred from the previous studies of (Mg,Fe)O ferropericlase, the observed reduction in the conductivity of perovskite at 70–85 GPa is most likely due to the high-spin to low-spin transition of iron; it decreases the number of unpaired electrons and therefore diminishes the conduction by electron hopping between the ferric and ferrous iron sites. Present conductivity data provide valuable implications for the pressure range of spin transition in (Mg,Fe)SiO3 perovskite, which has been highly controversial. The relatively abrupt reduction in the electrical conductivity above 70 GPa is reconciled with the spin-pairing transition in ferric iron, which may occur rather sharply at this pressure range.