Spin crossover in ferropericlase from first-principles molecular dynamics

TL;DR

This study uses first-principles molecular dynamics to map the spin crossover phase diagram of ferropericlase, revealing a broad coexistence region and semi-metallic conductivity at Earth's lower mantle conditions.

Contribution

It provides the first finite-temperature phase diagram of ferropericlase's spin crossover, highlighting the coexistence of magnetic states and semi-metallic behavior.

Findings

Broad pressure range with magnetic and non-magnetic ion coexistence

Ferropericlase exhibits semi-metallic electrical conductivity inside Earth

First-principles phase diagram of spin crossover at finite temperature

Abstract

Ferropericlase, (Mg,Fe)O, is the second-most abundant mineral of the Earth's lower mantle. With increasing pressure, the Fe ions in the material begin to collapse from a magnetic to non-magnetic spin state. We present a finite-temperature first-principles phase diagram of this spin crossover, finding a broad pressure range with coexisting magnetic and non-magnetic ions due to favorable enthalpy of mixing of the two. Furthermore, we find the electrical conductivity of the mineral to reach semi-metallic values inside the Earth.