Analysis of the multiferroicity in the hexagonal manganite YMnO3

TL;DR

This study clarifies the multiferroic behavior of YMnO3 by combining experimental measurements with symmetry analysis, revealing the magnetic group and the coupling between ferromagnetic and antiferromagnetic components.

Contribution

It identifies the magnetic group P6'3 as compatible with experimental data and elucidates the coupling mechanisms in YMnO3's multiferroic properties.

Findings

The magnetic group P6'3 fits all experimental data.

A small ferromagnetic component along c is induced by Dzyaloshinskii-Moriya interaction.

Ferromagnetic and antiferromagnetic components switch simultaneously.

Abstract

We performed magnetic and ferroelectric measurements, associated with Landau theory and symmetry analysis, in order to clarify the situation of the YMnO3 system, a classical example of type I multiferroics. We found that the only magnetic group compatible with all experimental data (neutrons scattering, magnetization,polarization, dielectric constant, second harmonic generation) is the P6'3 group. In this group a small ferromagnetic component along c is induced by the Dzyaloshinskii-Moriya interaction, and observed here in SQUID magnetization measurements. We found that the ferromagnetic and antiferromagnetic components can only be switched simultaneously, while the magnetic orders are functions of the polarization square and therefore insensitive to its sign.