Thermal treatment effects on PMN-0.4PT/Fe multiferroic heterostructures

TL;DR

This study investigates how thermal annealing influences the ferroelectric domain structure and magnetic properties of PMN-0.4PT/Fe heterostructures, revealing the ability to control interfacial strain and magnetic anisotropy through thermal treatment.

Contribution

It demonstrates how thermal annealing can modify ferroelectric domains and magnetic behavior in PMN-0.4PT/Fe heterostructures, providing insights for optimizing multiferroic device performance.

Findings

Thermal annealing alters ferroelectric domain orientation from out-of-plane to in-plane.

Intermediate annealing can stabilize a metastable ferroelectric domain configuration.

Magnetic properties of the Fe layer are affected by ferroelectric domain states via interfacial strain.

Abstract

Multiferroic heterostructures have gained in recent years a renewed role in spintronic applications due to their possibility in controlling the magnetic properties via interfacial coupling by exploiting the ferroelectric response to various external stimuli. Whereas the main mechanisms ruling the converse magnetoelectric coupling are considered as established, the research on how to optimize the ferroelectric properties is an active field. In particular the complex phase diagram of [Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-xPT) single crystals, that present relaxor ferroelectric and photovoltaic properties, deserves further investigation. For instance, crystalline quality and thermal stability of the ferroelectric domains in heterostructures need assessment. Here we show how, by thermal annealing over the ferroelectric Curie temperature and then cooling PMN-0.4PT/Fe heterostructures in inert atmosphere the domain population is significantly modified, evolving from a highly disordered, mostly out-of-plane domain population, to improved crystallinity and prevalent in-plane oriented domains. Upon further annealing, the domain population switches back to prevalent out-of-plane orientation suggesting that intermediate annealing steps can freeze PMN-0.4PT domain population in a metastable configuration. The structural analysis was carried out by combining micro-Raman and X-ray diffraction (XRD) measurements. In the three states the magnetic properties of interfacial Fe thin film are affected by the ferroelectric configurations as a consequence of changing interfacial strain, evolving from an isotropic behavior to an anisotropic one and back.