Effect of high pressure on multiferroicBiFeO3

Abstract

We report experimental evidence for pressure instabilities in the model multiferroic ${\text{BiFeO}}_3$ and, namely, reveal two structural phase transitions around 3.5 and 10 GPa by using diffraction and far-infrared spectroscopy at a synchrotron source. The intermediate phase crystallizes in a monoclinic space group, with octahedra tilts and small cation displacements. When the pressure is increased further the cation displacements (and thus the polar character) of ${\text{BiFeO}}_3$ is suppressed above 10 GPa. The nonpolar orthorhombic $Pnma$ structure observed above 10 GPa is in agreement with recent theoretical ab initio prediction, while the intermediate monoclinic phase has not been predicted theoretically.