Mao Kaihui, Zhang Jinlei, Guo Zijing, Liu Lizhe, Ma He, Chin Yiying, Lin Hongji, Bao Songsong, Xie Hangqing, Yang Run, Jing Zhaoyang, Shen Jiancang, Yuan Guoliang, Chen Jian, Wu Peiheng, Wu Xinglong
National Laboratory of Solid State Microstructures and Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Nanjing University, Nanjing 210093, P. R. China.
School and Mathematics and Physics, Suzhou University of Science and Technology, Suzhou, 215011, P. R. China.
J Am Chem Soc. 2020 Jul 22;142(29):12841-12849. doi: 10.1021/jacs.0c05845. Epub 2020 Jul 10.
Layered metal-organic structures (LMOSs) as magnetoelectric (ME) multiferroics have been of great importance for realizing new functional devices in nanoelectronics. Until now, however, achieving such room-temperature and single-phase ME multiferroics in LMOSs have proven challenging due to low transition temperature, poor spontaneous polarization, and weak ME coupling effect. Here, we demonstrate the construction of a LMOS in which four Ni-centered {NiNO} octahedra form in layer with asymmetric distortions using the coordination bonds between diphenylalanine molecules and transition metal Ni(II). Near room-temperature (283 K) ferroelectricity and ferromagnetism are observed to be both spontaneous and hysteretic. Particularly, the multiferroic LMOS exhibits strong magnetic-field-dependent ME polarization with low-magnetic-field control. The change in ME polarization with increasing applied magnetic field μ from 0 to 2 T decreases linearly from 0.041 to 0.011 μC/cm at the strongest ME coupling temperature of 251 K. The magnetic domains can be manipulated directly by applied electric field at 283 K. The asymmetrical distortion of Ni-centered octahedron in layer spurs electric polarization and ME effect and reduces spin frustration in the octahedral geometry due to spin-charge-orbital coupling. Our results represent an important step toward the production of room-temperature single-phase organic ME multiferroics.
作为磁电多铁性材料的层状金属有机结构（LMOSs）对于实现纳米电子学中的新型功能器件具有重要意义。然而，到目前为止，由于转变温度低、自发极化差以及磁电耦合效应弱，在LMOSs中实现室温单相磁电多铁性材料已被证明具有挑战性。在此，我们展示了一种LMOS的构建，其中四个以镍为中心的{NiNO}八面体通过二苯丙氨酸分子与过渡金属Ni(II)之间的配位键形成具有不对称畸变的层状结构。在接近室温（283 K）时，观察到铁电性和铁磁性都是自发的且具有滞后现象。特别地，这种多铁性LMOS在低磁场控制下表现出强烈的磁场依赖性磁电极化。在最强磁电耦合温度251 K下，随着外加磁场μ从0增加到2 T，磁电极化的变化从0.041线性降低到0.011 μC/cm。在283 K时，磁畴可以通过外加电场直接操控。层状结构中以镍为中心的八面体的不对称畸变激发了电极化和磁电效应，并由于自旋 - 电荷 - 轨道耦合降低了八面体几何结构中的自旋受挫。我们的结果代表了朝着生产室温单相有机磁电多铁性材料迈出的重要一步。
