title: Short range magnetic exchange interaction favors ferroelectricity.
abstract: Multiferroics, where two or more ferroic order parameters coexist, is one of the hottest fields in condensed matter physics and materials science. To search multiferroics, currently most researches are focused on frustrated magnets, which usually have complicated magnetic structure and low magnetic ordering temperature. Here, we argue that actually simple interatomic magnetic exchange interaction already contains a driving force for ferroelectricity, thus providing a new microscopic mechanism for the coexistence and strong coupling between ferroelectricity and magnetism. We demonstrate this mechanism by showing that even the simplest antiferromagnetic insulator like MnO, could display a magnetically induced ferroelectricity under a biaxial strain. In addition, we show that such mechanism also exists in the most important single phase multiferroics, i.e. BiFeO3, suggesting that this mechanism is ubiquitous in systems with superexchange interaction.
authors.affiliation: 1National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
authors.forename: Xiangang
authors.initials: X
authors.lastname: Wan
authors.affiliation: Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai, 200062, China.
authors.forename: Hang-Chen
authors.initials: HC
authors.lastname: Ding
authors.affiliation: Department of Physics, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Sergey Y
authors.initials: SY
authors.lastname: Savrasov
authors.affiliation: Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai, 200062, China.
authors.forename: Chun-Gang
authors.initials: CG
authors.lastname: Duan