The crystal and magnetic structures of BiFeO${}_3$ have been studied at high pressures up to 8.6 GPa by means of neutron powder diffraction at ambient temperature. Upon compression, a reduction of the spontaneous ferroelectric polarization is evidenced from the analysis of atomic displacements in the rhombohedral phase. A structural phase transition from the polar rhombohedral $R$3$c$ phase to the antipolar orthorhombic Pbam phase with antiferroelectic character of atomic displacements was revealed at $P$ = 3 GPa. The lattice parameters of the Pbam phase at $P$ = 4.1 GPa are $a$ = 5.5177(4), $b$ = 11.159(1) and $c$ = 7.7550(6) Å. The variation of the structural parameters of both phases as a function of pressure was determined. The initially incommensurate G-type antiferromagnetic structure of BiFeO${}_3$ becomes commensurate due to the structural phase transition.

• Received 22 June 2011

DOI:https://doi.org/10.1103/PhysRevB.84.094108