Magnetoelectric Coupling in Epitaxial Multiferroic BiFeO3–BaTiO3 Composite Thin Films

• Published in: physica status solidi (b) 2020-07, Vol.257 (7), p.n/a
• Main Authors: Hohenberger, Stefan, Lazenka, Vera, Selle, Susanne, Patzig, Christian, Temst, Kristiaan, Lorenz, Michael
• Format: Article
• Language: English
• Subjects: epitaxy; magnetoelectric effect; multiferroic multilayers; pulsed laser deposition; thin-film composites
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.201900613

Herein, the magnetoelectric (ME) performance of epitaxial multilayer composite films built from nanometer‐thick layers of multiferroic BiFeO3 and ferroelectric BaTiO3 is reviewed. A successful implementation of shadow‐mask pulsed laser deposition considerably reduces the interface and surface roughness of the multilayers. In dependence of double‐layer thickness and the degree of structural perfection, the multilayers show high ME voltage coefficients up to 480 V cm−1 Oe−1 at 300 K and 0 T bias magnetic field. With decreasing double‐layer thickness, an interface‐driven effect critically enhances the ME coupling in this strain and charge–comediated system. Interestingly, the characteristics of temperature and DC magnetic field dependencies of magnetoelectric voltage coefficients change with the transition from the 2D to 3D character of the single layers, i.e., for BiFeO3 layers thicker than 5 nm within the multilayers. These changes are attributed to variations of the contributing ME coupling mechanisms. Furthermore, scanning transmission electron microscopy (STEM) with energy‐dispersive X‐ray (EDX) spectroscopy mapping‐based nanoanalysis indicates that chemical effects at the interfaces play an important role for the ME performance of the BiFeO3–BaTiO3 multilayer thin films. Epitaxial multiferroic BiFeO3–BaTiO3 multilayers grown by shadow‐mask pulsed laser deposition with smooth interfaces show high magnetoelectric voltage coefficients αME up to 480 V cm−1 Oe−1 at 300 K and 0 T. The temperature dependence of αME points to a thickness‐dependent crossover from strain‐mediated to charge‐mediated magnetoelectric coupling in these thin‐film multilayers.