Microscopic origin of the giant ferroelectric polarization in tetragonal-like BiFeO3

We report direct experimental evidence for a room-temperature, ∼130μC/cm2 ferroelectric polarization from the tetragonal-like BiFeO 3 phase. The physical origin of this remarkable enhancement of ferroelectric polarization has been investigated by a combination of x-ray absorption spectroscopy, scanning transmission electron microscopy, and first principles calculations. A large strain-induced Fe-ion displacement relative to the oxygen octahedra, combined with the contribution of Bi 6s lone pair electrons, is the mechanism driving the large ferroelectric polarization in this tetragonal-like phase. © 2011 American Physical Society.