Local Structure and Spin Transition in Fe2O3 Hematite at High-Pressure

TL;DR

This study investigates how high pressure affects the local atomic structure and electronic spin state of Fe2O3 hematite, revealing that electronic spin transition drives structural changes at pressures up to 79 GPa.

Contribution

First to determine the pressure evolution of Fe2O3 hematite's local structure using extended X-ray absorption fine structure up to 79 GPa, linking electronic and structural transitions.

Findings

Orthorhombic Aba2 structure is most probable at high pressure.

Spin transition from high-spin to low-spin occurs with increasing pressure.

Electronic transition drives the structural change, not vice versa.

Abstract

The pressure evolution of the local structure of Fe2O3 hematite has been determined for the first time by extended x-ray absorption fine structure up to 79 GPa. The comparison to the different high-pressure forms proposed in the literature suggests that the orthorhombic structure with space group Aba2 is the most probable. The crossover from Fe high-spin to low-spin states with pressure increase has been monitored from the pre-edge region of the Fe K-edge absorption spectra. The "simultaneous" comparison with the local structural changes allows us to definitively conclude that it is the electronic transition that drives the structural transition and not viceversa.