Enhanced Magnetoelectric Coupling in BaTiO-BiFeO Multilayers-An Interface Effect.

Combining various (multi-)ferroic materials into heterostructures is a promising route to enhance their inherent properties, such as the magnetoelectric coupling in BiFeO3 thin films. We have previously reported on the up-to-tenfold increase of the magnetoelectric voltage coefficient α ME in BaTiO3-BiFeO3 multilayers relative to BiFeO3 single layers. Unraveling the origin and mechanism of this enhanced effect is a prerequisite to designing new materials for the application of magnetoelectric devices. By careful variations in the multilayer design we now present an evaluation of the influences of the BaTiO3-BiFeO3 thickness ratio, oxygen pressure during deposition, and double layer thickness. Our findings suggest an interface driven effect at the core of the magnetoelectric coupling effect in our multilayers superimposed on the inherent magnetoelectric coupling of BiFeO3 thin films, which leads to a giant α ME coefficient of 480 V c m -1 Oe-1 for a 16 × (BaTiO3-BiFeO3) superlattice with a 4 . 8 nm double layer periodicity.