Giant sharp magnetoelectric switching in multiferroic epitaxial La_{0.67}Sr_{0.33}MnO_3 on BaTiO_3

TL;DR

This study demonstrates a giant, sharp magnetoelectric switching effect at a single epitaxial interface between a ferromagnetic La_{0.67}Sr_{0.33}MnO_3 film and a BaTiO_3 substrate, with potential applications in sensors and memory devices.

Contribution

It reports a novel, large magnetoelectric coupling at a single interface driven by strain from ferroelastic domains, surpassing previous coupling strengths in similar materials.

Findings

Achieved up to 65% change in magnetization with small electric fields.

Observed coupling strength of 2.3×10^{-7} s/m, larger than prior reports.

Coupling persists near room temperature, suitable for practical applications.

Abstract

Magnetoelectric coupling permits a magnetic order parameter to be addressed electrically or vice versa, and could find use in data storage, field sensors and actuators. Coupling constants for single phase materials such as chromium dioxide, boracites and manganites are typically as low as 10^{-12} - 10^{-9} s/m, e.g. because the polarisations and magnetisations are small. Two phase multiferroics with strain mediated coupling, such as laminates, composites and epitaxial nanostructures, are more promising because each phase may be independently optimised. The resulting magnetoelectric switching can be larger, e.g. 10^{-8} s/m, but it is not sharp because clean coupling is precluded by the complexity of the microstructures and concomitant strain fields. Here we report a giant sharp magnetoelectric effect at a single epitaxial interface between a 40 nm ferromagnetic stress-sensitive La_{0.67}Sr_{0.33}MnO_3 film, and a 0.5 mm BaTiO_3 substrate that is ferroelectric, piezoelectric and ferroelastic. By applying a small electric field (4-10 kV/cm) across the entire structure, we achieve persistent changes in film magnetisation of up to 65% near the BaTiO_3 structural phase transition at around 200 K. This represents a giant magnetoelectric coupling (2.3*10-7 s/m) that arises from strain fields due to ferroelastic non-180 degree domains whose presence we confirm using x-ray diffraction. The coupling persists over a wide range of temperatures including room temperature, and could therefore inspire a range of sensor and memory applications.