Interfacial Coupling in Multiferroic-Ferromagnet Heterostructures

TL;DR

This study investigates the magnetic coupling at the interface of BiFeO3 and CoFe0.9Fe0.1 films, revealing how multiferroic properties influence ferromagnetic behavior and how this coupling diminishes with ultrathin BiFeO3 layers.

Contribution

It provides detailed local probe measurements of interfacial magnetic coupling in multiferroic-ferromagnet heterostructures, highlighting the effects of film thickness on exchange interactions.

Findings

Uniaxial magnetic anisotropy observed.

Effective coupling field around 10 mT.

Coupling weakens significantly for 3 nm BiFeO3 films.

Abstract

We report local probe investigations of the magnetic interaction between BiFeO3 films and a ferromagnetic Co0.9Fe0.1 layer. Within the constraints of intralayer exchange coupling in the Co0.9Fe0.1, the multiferroic imprint in the ferromagnet results in a collinear arrangement of the local magnetization and the in-plane BiFeO3 ferroelectric polarization. The magnetic anisotropy is uniaxial, and an in-plane effective coupling field of order 10 mT is derived. Measurements as a function of multiferroic layer thickness show that the influence of the multiferroic layer on the magnetic layer becomes negligible for 3 nm thick BiFeO3 films. We ascribe this breakdown in the exchange coupling to a weakening of the antiferromagnetic order in the ultrathin BiFeO3 film based on our X-ray linear dichroism measurements. These observations are consistent with an interfacial exchange coupling between the CoFe moments and a canted antiferromagnetic moment in the BiFeO3.