Origin of the large polarization in multiferroic YMnO$_3$ thin films revealed by soft and hard x-ray diffraction

TL;DR

This study reveals that the large polarization in orthorhombic YMnO3 thin films originates from coexisting E-type and cycloidal magnetic states, with E-type states playing a key role in polarization enhancement.

Contribution

It provides new insights into the magnetic structure and polarization mechanism of YMnO3 thin films using advanced x-ray diffraction techniques.

Findings

Incommensurate magnetic reflection appears below 45 K.

Commensurate lattice distortion occurs below 35 K.

E-type antiferromagnetic states are responsible for large polarization.

Abstract

We investigated the magnetic structure of an orthorhombic YMnO3 thin film by resonant soft x-ray and hard x-ray diffraction. We observed a temperature-dependent incommensurate magnetic reflection below 45 K and a commensurate lattice-distortion reflection below 35 K. These results demonstrate that the ground state is composed of coexisting E-type and cycloidal states. Their different ordering temperatures clarify the origin of the large polarization to be caused by the E-type antiferromagnetic states in the orthorhombic YMnO3 thin film.