摘要：Multiferroic materials exhibit more than one of the primary ferroic order parameters of (anti-)ferromagnetism, ferroelectricity and ferroelasticity. The cross couplings between these order parameters lead to new phenomena, resulting in new potential application in electronics, spintronics. Here, we discussed the coupling between polarization and magnetization, and coupling between strain and optical properties in multiferroics and ferroelectrics. The coupling between electrical polarization and magnetic moment usually is very weak. We proposed indirect coupling effects between polarization and magnetization in perovskite BiFeO₃ films and superlattices BaTiO₃/ReTiO₃ films by first-principles [1-3]. This effect can be viewed as a two-step process: Switching the polarization first results in the change of the sense of the rotation of the oxygen octahedra, which in turn induces the switching of the magnetic order parameter. On the other hand, the effect of strain on refractive index (elasto-optic effect) is only studied in a few ferroelectric and multiferroic materials. We investigate, both from experiments and first-principle techniques, if and how epitaxial strain engineering can tune the optical response of BiFeO₃ and PbTiO₃ thin films [4,5]. We find a very large variation of the optical index with strain in BiFeO₃ and PbTiO₃ thin films, corresponding to an effective elasto-optic coefficient larger than that of quartz. The origin of such large conversion between elastic and optical properties is further elucidated. Our findings broaden the potential of multiferroics towards spintronics, photonics and thin film acousto-optic devices, and suggest exciting device opportunities arising from the coupling of ferroic, piezoelectric and optical responses.

1.Yurong Yang, Massimiliano Stengel, Wei Ren, X. H. Yan, and L. Bellaiche, Physical Review B 86, 144114 (2012).

2.Yurong Yang, Wei Ren, Dawei Wang, and L. Bellaiche, Physical Review Letters 109, 267602 (2012).

3.Yurong Yang, Jorge Iniguez, Ai-Jie Mao, L. Bellaiche, “Prediction of a Novel Magnetoelectric Switching Mechanism in Multiferroics,” Physical Review Letters 112, 057202 (2014).

4.D. Sando+, Yurong Yang+, E. Bousquet, C. Carrétéro, V. Garcia, S. Fusil, D. Dolfi,A. Barthélémy, Ph. Ghosez, L. Bellaiche and M. Bibes, Nature Communications 7, 10718 (2016)

5.L. Chen, Yurong Yang*, Z. Gui, D. Sando, M. Bibes, X. K. Meng, L. Bellaiche, Physical Review Letters 115, 267602 (2015).

报告人简介:  Yurong Yang is a Research Associate Professor in the Department of Physics at University of Arkansas. He received his PH.D degree from Nanjing University of Aeronautics and Astronautics in 2010. And He came to the University of Arkansas (Fayetteville, USA) as a Research Associate in 2011, and was promoted to Research Assistant Professor in 2014 and then to Research Associate Professor in 2017. Dr. Yang published around 50 scientific articles, including 2 papers in Nature Communications, 6 in Physical Review Letters and 17 in Physical Review B. His latest findings open new perspectives for applications of multiferroics and ferroelectrics.