Pressure-Induced Intermediate-to-Low Spin State Transition in LaCoO3

TL;DR

This study uses synchrotron X-ray diffraction to investigate how pressure induces a transition from an intermediate to a low-spin state in LaCoO3, revealing unique compressibility behavior linked to electronic state changes.

Contribution

It demonstrates pressure as a tool to induce and study spin state transitions in LaCoO3, highlighting the relationship between pressure, crystal field splitting, and ionic size.

Findings

Anomalously low bulk compressibility of 150 GPa observed.

Large initial bond compressibility of 4.8e-3 GPa-1 levels off near 4 GPa.

Depopulation of the intermediate spin state driven by increased crystal field splitting.

Abstract

Synchrotron X-ray powder diffraction experiments reveal that the transition from a magnetic intermediate spin (IS) state to a nonmagnetic low-spin (LS) ground state in LaCoO3 normally observed when cooling, manifests itself under pressure by an anomalously low bulk compressibility of 150(2) GPa and an initially very large bond compressibility of 4.8e-3 GPa-1 which levels off near 4 GPa. The continuous depopulation of the IS state is driven by an increased crystal field splitting resulting in an effective reduction of the size of the Co3+ cation.