Zhang Jinlei, Wu Shuyi, Shan Yun, Guo JunHong, Yan Shuo, Xiao Shuyu, Yang Chunbing, Shen Jiancang, Chen Jian, Liu Lizhe, Wu Xinglong
National Laboratory of Solid State Microstructures and Department of Physics , Nanjing University , Nanjing 210093 , P.R. China.
China Key Laboratory of Advanced Functional Materials of Nanjing , Nanjing Xiaozhuang University , Nanjing 210093 , P.R. China.
ACS Nano. 2019 Feb 26;13(2):2334-2340. doi: 10.1021/acsnano.8b09058. Epub 2019 Feb 11.
Two dimensional (2D) materials possessing ferroelectric/ferromagnetic orders and especially low-magnetic-field controlled magnetoelectricity have great promise in spintronics and multistate data storage. However, ferroelectric and magnetoelectric (ME) dipoles in the atom-thick 2D materials are difficult to be realized due to structural inversion symmetry, thermal actuation, and depolarized field. To overcome these difficulties, the monolayer structure must possess an in-plane inversion asymmetry in order to provide out-of-plane ferroelectric polarization. Herein, crystal chemistry is adopted to engineer specific atomic displacement in monolayer ReS to change the crystal symmetry to induce out-of-plane ferroelectric polarization at room temperature. The cationic Re vacancy in the atom-displaced ReS monolayer causes spin polarization of two immediate neighbor sulfur atoms to generate magnetic ordering, and the ferroelectric distortion near the Re vacancy locally tunes the ferromagnetic order thereby triggering low-magnetic-field controlled ME polarization at about 28 K. As a result, 2D ME coupling multiferroics is achieved. Our results not only reveal a design methodology to attain coexistence of ferroelectric and ferromagnetic orders in 2D materials but also provide insights into magnetoelectricity in 2D materials.
具有铁电/铁磁序，特别是具有低磁场控制磁电效应的二维（2D）材料在自旋电子学和多态数据存储方面具有巨大潜力。然而，由于结构反演对称性、热驱动和去极化场，原子级厚度的二维材料中的铁电和磁电（ME）偶极难以实现。为了克服这些困难，单层结构必须具有面内反演不对称性，以提供面外铁电极化。在此，采用晶体化学方法设计单层ReS中特定的原子位移，以改变晶体对称性，从而在室温下诱导出面外铁电极化。原子位移后的ReS单层中的阳离子Re空位导致两个紧邻的硫原子产生自旋极化，从而产生磁有序，并且Re空位附近的铁电畸变局部调节铁磁序，进而在约28 K时触发低磁场控制的ME极化。结果，实现了二维ME耦合多铁性材料。我们的结果不仅揭示了一种在二维材料中实现铁电和铁磁序共存的设计方法，还为二维材料中的磁电效应提供了见解。
