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Epitaxial Coherence at Interfaces as Origin of High Magnetoelectric Coupling in Multiferroic BaTiO 3 –BiFeO 3 Superlattices
Author(s) -
Lorenz Michael,
Lazenka Vera,
Schwinkendorf Peter,
Van Bael Margriet J.,
Vantomme André,
Temst Kristiaan,
Grundmann Marius,
Höche Thomas
Publication year - 2016
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201500822
Subject(s) - materials science , multiferroics , superlattice , condensed matter physics , ferroelectricity , epitaxy , magnetic field , dielectric , optoelectronics , nanotechnology , layer (electronics) , physics , quantum mechanics
Multiferroic superlattices consisting of 15 double layers BaTiO 3 –BiFeO 3 show a very high magnetoelectric voltage coefficient α ME of up to 49 V cm −1 Oe −1 at 300 K, measured at 1 kHz with zero direct current (DC) bias magnetic field. However, the microscopic origins of such high α ME values, and the temperature and DC magnetic field dependencies of α ME are not understood up to now. Therefore, in this study two superlattices grown at high/low oxygen partial pressures having high/low α ME values, respectively, are compared. While at high growth pressure the strain contrast in high‐resolution transmission electron microscopy images is limited to few layers at the substrate interface, the low‐pressure sample shows much more pronounced microstrain. This is additionally visualized in Fourier transformed images, and the out‐of‐plane lattice parameter of the single BaTiO 3 layer is increased near the interface. In addition to a low density of oxygen vacancies, it seems to be important to avoid micromechanical clamping of the 2D single‐phase nanolayers of the multiferroic BaTiO 3 –BiFeO 3 superlattices to achieve high magnetoelectric coupling.