Polarization control at spin-driven ferroelectric domain walls.

Naëmi Leo,Bernd Lorenz,Andres Cano,Dennis Meier,Manfred Fiebig,Anders Bergman,Narayan Poudel

doi:10.1038/ncomms7661

Abstract

Unusual electronic states arise at ferroelectric domain walls due to the local symmetry reduction, strain gradients and electrostatics. This particularly applies to improper ferroelectrics, where the polarization is induced by a structural or magnetic order parameter. Because of the subordinate nature of the polarization, the rigid mechanical and electrostatic boundary conditions that constrain domain walls in proper ferroics are lifted. Here we show that spin-driven ferroelectricity promotes the emergence of charged domain walls. This provides new degrees of flexibility for controlling domain-wall charges in a deterministic and reversible process. We create and position a domain wall by an electric field in Mn0.95Co0.05WO4. With a magnetic field we then rotate the polarization and convert neutral into charged domain walls, while its magnetic properties peg the wall to its location. Using atomistic Landau-Lifshitz-Gilbert simulations we quantify the polarization changes across the two wall types and highlight their general occurrence.

Highlights

Unusual electronic states arise at ferroelectric domain walls due to the local symmetry reduction, strain gradients and electrostatics
Our results show that the polarization state at spin-driven ferroelectric domain walls can readily be manipulated by applying magnetic fields
By moving the polarization with respect to the walls, but not the walls with respect to the polarization, we demonstrate a new route for modifying the charge configuration of ferroelectric domain walls dynamically in a fully reversible process

Summary

Introduction

Unusual electronic states arise at ferroelectric domain walls due to the local symmetry reduction, strain gradients and electrostatics. This applies to improper ferroelectrics, where the polarization is induced by a structural or magnetic order parameter. The boundary conditions imposed by the primary order parameter dominate so that unusual ferroelectric domain-wall configurations are readily stabilized even in the as-grown state. Besides promoting the emergence of charged ferroelectric domain walls, the coupling to the primary order parameter provides a promising but so far unexplored handle to act on the local polarization by means other than electric fields, such as mechanical stress or magnetic fields. Our results show that the polarization state at spin-driven ferroelectric domain walls can readily be manipulated by applying magnetic fields. By moving the polarization with respect to the walls, but not the walls with respect to the polarization, we demonstrate a new route for modifying the charge configuration of ferroelectric domain walls dynamically in a fully reversible process

Methods

Results

Conclusion