Electrical resistivity of Fe3O4to 48 GPa: Compression-induced changes in electron hopping at mantle pressures

摘要: We have measured the electrical resistivity of Fe3O4 to pressures 48 GPa at temperatures between 258 and 300 K in order evaluate compression-induced changes electron exchange divalent trivalent iron ions. At ambient pressures, inverse spinel-structured magnetite is well known for its hopping octahedral sites, our results thus provide constraints on role intervalence charge transfer altering iron-rich phases. The decreases by more than an magnitude 0 ∼20 GPa, where it reaches a minimum, subsequently increasing factor 2 GPa. This finding implies that electronic Fe2+ Fe3+ ions notably enhanced initial 7% volumetric compression but marginally impeded higher compressions. associate this discontinuity slope with phase transition from spinel structure monoclinic Both previous Mossbauer work small change indicate persists as mechanism transport through transition. these within characteristic metallic values, measurements temperature dependence demonstrate high-pressure remains semiconducting. However, 1–2 orders less Fe0.94O illustrating profound effect (particularly high pressures) properties oxides. By measuring 12 K, we also constrain pressure activation enthalpy conduction Fe3O4. volume dependent low-pressure (magnetite) phase. Such behavior simulations mantle use constant may underestimate lower mantle. shifts iron-wustite, wustite-magnetite, magnetite-hematite, wustite-hematite oxygen fugacity buffers depth assess conditions could generate mixed valence compounds