Pressure induced spin crossover in disordered {\alpha}-LiFeO2

TL;DR

This study investigates how high pressure induces a gradual spin crossover in disordered { extalpha}-LiFeO2, affecting its structural, magnetic, and electrical properties without reaching metallicity even at 200 GPa.

Contribution

It provides the first detailed analysis of pressure-induced spin crossover in disordered { extalpha}-LiFeO2, revealing a sluggish transition and its effects on properties up to 100 GPa.

Findings

Crystal structure remains stable up to 82 GPa.

Gradual Fe3+ high- to low-spin transition begins at 50 GPa.

Material remains semiconducting even at 115 GPa.

Abstract

Structural, magnetic and electrical-transport properties of {\alpha}-LiFeO2, crystallizing in the rock salt structure with random distribution of Li and Fe ions, have been studied by synchrotron X-ray diffraction, 57Fe M\"ossbauer spectroscopy and electrical resistance measurements at pressures up to 100 GPa using diamond anvil cells. It was found that the crystal structure is stable at least to 82 GPa, though a significant change in compressibility has been observed above 50 GPa. The changes in the structural properties are found to be on a par with a sluggish Fe3+ high- to low-spin (HS-LS) transition (S=5/2 to S=1/2) starting at 50 GPa and not completed even at ~100 GPa. The HS-LS transition is accompanied by an appreciable resistance decrease remaining a semiconductor up to 115 GPa and is not expected to be metallic even at about 200 GPa. The observed feature of the pressure-induced HS-LS transition is not an ordinary behavior of ferric oxides at high pressures. The effect of Fe3+ nearest and next nearest neighbors on the features of the spin crossover is discussed.