Control of multiferroic order by magnetic field in frustrated helimagnet MnI$_2$. Theory

TL;DR

This paper presents a theoretical model explaining how magnetic fields influence the multiferroic order in frustrated helimagnet MnI2, capturing experimental observations of electric polarization behavior and ferroelectricity suppression.

Contribution

It offers a novel theoretical framework that accounts for the interplay of various interactions in MnI2, explaining its multiferroic response to magnetic fields.

Findings

Electric polarization changes direction with magnetic field rotation.

Ferroelectricity disappears above a critical magnetic field.

The model aligns with recent experimental results.

Abstract

We provide a theoretical description of frustrated multiferroic $\rm MnI_2$ with a spiral magnetic ordering in magnetic field $\bf h$. We demonstrate that subtle interplay of exchange coupling, dipolar forces, hexagonal anisotropy, and the Zeeman energy account for the main experimental findings observed recently in this material (Kurumaji, et al., Phys.\ Rev.\ Lett.\ {\bf 106}, 167206 (2011)). We describe qualitatively the non-trivial evolution of electric polarization $\bf P$ upon $\bf h$ rotation, changing $\bf P$ direction upon $h$ increasing, and disappearance of ferroelectricity at $h>h_c$, where $h_c$ is smaller than the saturation field.