Correlation of magnetoelectric coupling in multiferroic BaTiO3-BiFeO3 superlattices with oxygen vacancies and antiphase octahedral rotations

Multiferroic (BaTiO3-BiFeO3) x 15 multilayer heterostructures show high magnetoelectric (ME) coefficients alpha(ME) up to 24 V/cm.Oe at 300 K. This value is much higher than that of a single-phase BiFeO3 reference film (alpha(ME) = 4.2 V/cm.Oe). We found clear correlation of ME coefficients with increasing oxygen partial pressure during growth. ME coupling is highest for lower density of oxygen vacancy-related defects. Detailed scanning transmission electron microscopy and selected area electron diffraction microstructural investigations at 300 K revealed antiphase rotations of the oxygen octahedra in the BaTiO3 single layers, which are an additional correlated defect structure of the multilayers. (C) 2015 AIP Publishing LLC.