Magnetic-field control of the electric polarization inBiMnO3

Abstract

We present the microscopic theory of improper multiferroicity in ${\text{BiMnO}}_{3}$, which can be summarized as follows: (1) the ferroelectric polarization is driven by the hidden antiferromagnetic order in the otherwise centrosymmetric $C2/c$ structure; (2) the relativistic spin-orbit interaction is responsible for the canted spin ferromagnetism. Our analysis is supported by numerical calculations of electronic polarization using the Berry-phase formalism, which was applied to the low-energy model of ${\text{BiMnO}}_{3}$ derived from the first-principles calculations. We explicitly show how the electric polarization can be controlled by the magnetic field and argue that ${\text{BiMnO}}_{3}$ is a rare and potentially interesting material where ferroelectricity can indeed coexist and interplay with the ferromagnetism.