四方相多铁BiMnO_3电控磁性的理论研究

钙钛矿结构BiMnO_3作为同时具有铁电性与铁磁性的多铁材料,在人工神经网络方面可以作为一种潜在的人工突触材料,从而设计出新型多铁人工突触器件.本文使用第一性原理计算的方法,分别研究了四方相BiMnO_3在xy面内施加0.18%与4%应力条件下的铁电情况,以及Mn原子磁矩随着铁电极化强度变化的曲线.结果表明,在四方相多铁BiMnO_3中,Mn原子磁矩会随着极化强度的增强而增大,表示其铁磁性可以在一定程度上由其铁电极化来进行调控,并且应力越大,其磁矩变化范围就越大.这一结果使得多铁BiMnO_3在人工突触器件设计方面拥有潜在的应用价值,多铁性使其在作为人工突触器件材料中具有更多可调控的自由度,从而可用于模拟多突触连接.这可为将来构造类脑芯片打下一定的理论基础.

Theoretical study on magnetoelectric effect in multiferroic tetragonal BiMnO3

Perovskite BiMnO₃ with ferroelectric and ferromagnetic ordering simultaneously, as a kind of multiferroics, can be expected to have the coupling between the magnetic and dielectric properties as well as their control by the application of electric fields. This advantage can make BiMnO₃ a good candidate for an artificial synapse material. Under the framework of the density functional theory, in this paper we adopt the generalized gradient approximation (GGA+U) plane wave pseudopotential method to calculate the ferroelectricity double-well potential curves and magnetic moments of Mn of tetragonal BiMnO₃, with 0.18% and 4% strain exerted in its x-y plane. The results show that the magnetic moment of Mn monotonically increases from paraelectric state to ferroelectric state. It means that the ferromagnetic property of tetragonal BiMnO₃ can be controlled by the intensity of polarization. The greater the stress, the greater the range of magnetic moment is. This would imply that the multiferroic artificial synapse device based on BiMnO₃ can bring another degree of freedom into designing the complex cognitive systems of artificial intelligence in the future.