Ferroelectricity in perovskite $HoMnO_3$ and $YMnO_3$

TL;DR

This paper reports the observation of ferroelectricity in orthorhombic HoMnO3 and YMnO3, linking it to magnetic phase transitions and theoretical models involving magnetic structure-driven polarization.

Contribution

It demonstrates ferroelectricity in these compounds at specific magnetic transitions and discusses the results within recent theoretical frameworks.

Findings

Ferroelectricity appears at magnetic lock-in transitions.

Polarization in HoMnO3 depends on external magnetic field.

Results align with double exchange driven polarization models.

Abstract

Ferroelectricity is observed in orthorhombic $HoMnO_3$ and $YMnO_3$ at the magnetic lock-in transitions into an E-type structure or an incommensurate phase with a temperature independent wave vector, respectively. In $HoMnO_3$ the ferroelectric polarization strongly depends on the external magnetic field indicating the involvement of the rare earth moment order in this compound. The results are discussed within the framework of recent theoretical models, in particular the double exchange driven polar displacements predicted for E-type magnetic structures.