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 to 10^-9 s m^-1, 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^-1, but it is not sharp because clean coupling is precluded by the complexity of the microstructures and concomitant strain fields. I will report a giant sharp magnetoelectric effect at a single epitaxial interface between a 40 nm ferromagnetic stress-sensitive La0.67Sr0.33MnO3 film, and a 0.5 mm BaTiO3 substrate that is ferroelectric, piezoelectric and ferroelastic. By applying a small electric field (4 10 kV cm^-1) across the entire structure, persistent changes in film magnetisation of up to 65% are achieved near the BaTiO3 structural phase transition at ~200 K. This represents a giant magnetoelectric coupling (2.3 X 10 ^-7 s m^-1) that arises from strain fields due to ferroelastic non-180° domains whose presence are confirmed 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.