Tailoring ferromagnetism through electrically controlled morphology

TL;DR

This paper demonstrates a novel method to control ferromagnetism in heterostructures by electrically inducing reversible morphological changes on the surface of ferroelectric substrates, affecting magnetic responses.

Contribution

It introduces a new approach where morphological modifications, controlled electrically, influence magnetoelectric coupling in heterostructures, expanding the mechanisms beyond charge, strain, or ion migration.

Findings

Reversible surface cracks form and disappear with electric field switching.

Magnetic response varies up to 2.5 times with morphological changes.

Surface morphology significantly impacts magnetoelectric coupling.

Abstract

Converse magnetoelectric coupling in artificial multiferroics is generally modelled through three possible mechanisms: charge transfer, strain mediated or ion migration. Here we demonstrate a novel and highly reliable approach, where electrically controlled morphological modifications control the ferromagnetic response of a magnetoelectric heterostructure, specifically FexMn1-x ferromagnetic films on ferroelectric PMN-PT (001) substrates. The ferroelectric PMN-PT substrates present, in correspondence to electrical switching, fully reversible morphological changes at the surface, to which correspond reproducible modifications of the ferromagnetic response of the FexMn1-x films. Topographic analysis by atomic force microscopy shows the formation of surface cracks after application of a positive electric field up to 6 kV/cm, which disappear after application of negative voltage of the same amplitude. In-operando x-ray magnetic circular dichroic spectroscopy at Fe edge in FexMn1-x layers shows local variations of dichroic signal up to a factor 2.5 as a function of the electrically-driven morphological state. These findings highlight the role of morphology and surface topography as a key aspect in magnetoelectric coupling, whose proof of electrically reversible modification of the magnetic response adds a new possibility in the design of multiferroic heterostructures with electrically controlled functionalities.