Properties of ${\text{BiFeO}}_3$ under high magnetic fields applied in the plane perpendicular to the polarization are investigated via an original first-principles-based effective Hamiltonian. Different phenomena are found, depending if the magnetic fields lie (a) along the initial direction of the antiferromagnetic vector, (b) perpendicular to it, or (c) in between these two latter directions. For instance, a spin-flop transition occurs for case (a), while a continuous transition occurs, for which both the antiferromagnetic vector and the field-induced magnetization rotate, for case (c). Such latter rotation leads to a controllable large enhancement of the magnetoelectric coefficient.

• Received 28 November 2008

DOI:https://doi.org/10.1103/PhysRevB.79.012101