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.
Highlights
Multiferroics, where two or more ferroic order parameters coexist, is one of the hottest fields in condensed matter physics and materials science
Currently most researches are focused on frustrated magnets, which usually have complicated magnetic structure and low magnetic ordering temperature
We argue that simple interatomic magnetic exchange interaction already contains a driving force for ferroelectricity, providing a new microscopic mechanism for the coexistence and strong coupling between ferroelectricity and magnetism
Summary
Xiangang Wan[1,2], Hang-Chen Ding[3], Sergey Y. This magnitude is smaller than our estimated one possibly due to the much larger MnO bond (~2.2 Å), but it demonstrates that off-center motion of the anion between two magnetic cations would enhance the magnetic exchange interaction. Regardless the temperature (T = 200, 300 and 400 K) and U, give the same qualitative conclusion: losing the magnetic ordering will suppress the off-center displacement, and even a large strain (− 5%) can no longer induce the ferroelectric instability for PM phase (see Supplementary Materials for details). Our research provides a new way to explain the coexistence of ferroelectricity and magnetism and might be useful to the search of novel multiferroics suitable of practical use
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