Strain Coupled Domains in BaTiO3(111)-CoFeB Heterostructures

TL;DR

This study demonstrates how ferroelectric domains in BaTiO3 influence magnetic domains in CoFeB heterostructures, enabling control of magnetic domain wall properties through strain coupling for potential low-power device applications.

Contribution

It provides direct imaging and analysis of strain-coupled ferroelectric and ferromagnetic domains, revealing how domain configurations affect magnetic easy axes and domain wall characteristics.

Findings

Magnetic easy axes are aligned at 60° or 120° to ferroelectric polarization changes.

Charged and uncharged magnetic domain walls are observed depending on magnetic history.

Domain wall width can be tuned from 192 nm to 119 nm via magnetic field, enabling strain-mediated control.

Abstract

Domain pattern transfer from ferroelectric to ferromagnetic materials is a critical step for the electric field control of magnetism and has the potential to provide new schemes for low-power data storage and computing devices. Here we investigate domain coupling in BaTiO$_3$(111)/CoFeB heterostructures by direct imaging in a wide-field Kerr microscope. The magnetic easy axis is found to locally change direction as a result of the underlying ferroelectric domains and their polarisation. By plotting the remanent magnetisation as a function of angle in the plane of the CoFeB layer, we find that the magnetic easy axes in adjacent domains are angled at 60$^\circ$ or 120$^\circ$, corresponding to the angle of rotation of the polarisation from one ferroelectric domain to the next, and that the magnetic domain walls may be charged or uncharged depending on the magnetic field history. Micromagnetic simulations show that the properties of the domain walls vary depending on the magnetoelastic easy axis configuration and the charged or uncharged nature of the wall. The configuration where the easy axis alternates by 60$^\circ$ and a charged wall is initialised exhibits the largest change in domain wall width from 192 nm to 119 nm as a function of in-plane magnetic field. Domain wall width tuning provides an additional degree of freedom for devices that seek to manipulate magnetic domain walls using strain coupling to ferroelectrics.