Magnetic-field control of the electric polarization in BiMnO3

TL;DR

This paper develops a microscopic theory explaining how magnetic order influences electric polarization in BiMnO3, highlighting the role of spin-orbit interaction and demonstrating control of ferroelectricity via magnetic fields.

Contribution

It introduces a detailed microscopic model of multiferroicity in BiMnO3, linking magnetic order, spin-orbit effects, and electric polarization, supported by first-principles calculations.

Findings

Electric polarization driven by hidden antiferromagnetic order.

Spin-orbit interaction causes canted spin ferromagnetism.

Electric polarization can be controlled by magnetic field.

Abstract

We present the microscopic theory of improper multiferroicity in BiMnO3, 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 Berry's phase formalism, which was applied to the low-energy model of BiMnO3 derived from the first-principles calculations. We explicitly show how the electric polarization can be controlled by the magnetic field and argue that BiMnO3 is a rare and potentially interesting material where ferroelectricity can indeed coexist and interplay with the ferromagnetism.