Motivated by the seminal theoretical prediction of strain-induced ferroelectricity in binary oxides done in 2010 [E. Bousquet, N. A. Spaldin & Ph. Ghosez, Phys. Rev. Lett. 104, 037601 (2010)],the possible appearance of ferroelectricity in ferromagnetic EuO under epitaxial strain has been investigated in thin films and superlattices. Achieving compressive epitaxial strains up to more than 6%, the study confirms the original theoretical prediction, making strained EuO the simplest known multiferroic material.
Making EuO multiferroic by epitaxial strain engineering, V. Gian, R. Held, E. Bousquet, Y. Yuan, A. Melville, H. Zhou, V. Gopalan, Ph. Ghosez, N. A. Spaldin, D. G. Schlom & S. Kamba, Communications Materials 1, 74 (2020).