Effect of high pressure on multiferroic BiFeO3

TL;DR

This study investigates how high pressure affects the structural phases of multiferroic BiFeO3, revealing two phase transitions and changes in ferroelectric properties through experimental diffraction and spectroscopy methods.

Contribution

First experimental evidence of pressure-induced phase transitions in BiFeO3, including an unpredicted monoclinic phase between 3 and 9 GPa.

Findings

Identified two structural phase transitions at 3 GPa and 10 GPa.

Discovered an intermediate monoclinic phase not predicted by theory.

Observed suppression of ferroelectric cation displacements above 10 GPa.

Abstract

We report experimental evidence for pressure instabilities in the model multiferroic BiFeO3 and namely reveal two structural phase transitions around 3 GPa and 10 GPa by using diffraction and far-infrared spectroscopy at a synchrotron source. The intermediate phase from 3 to 9 GPa crystallizes in a monoclinic space group, with octahedra tilts and small cation displacements. When the pressure is further increased the cation displacements (and thus the polar character) of BiFeO3 is suppressed above 10 GPa. The above 10 GPa observed non-polar orthorhombic Pnma structure is in agreement with recent theoretical ab-initio prediction, while the intermediate monoclinic phase was not predicted theoretically.