Zhong Tingting, Zhang Hong, Wu Menghao
Department of Physics, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, China.
School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China.
Research (Wash D C). 2024 Aug 5;7:0428. doi: 10.34133/research.0428. eCollection 2024.
In recent years, the unique mechanism of sliding ferroelectricity with ultralow switching barriers has been experimentally verified in a series of 2-dimensional (2D) materials. However, its practical applications are hindered by the low polarizations, the challenges in synthesis of ferroelectric phases limited in specific stacking configurations, and the low density for data storage since the switching process involves large-area simultaneous sliding of a whole layer. Herein, through first-principles calculations, we propose a type of semi-sliding ferroelectricity in the single metal porphyrin molecule intercalated in 2D bilayers. An enhanced vertical polarization can be formed independent on stacking configurations and switched via sliding of the molecule accompanied by the vertical displacements of its metal ion anchored from the upper layer to the lower layer. Such semi-sliding ferroelectricity enables each molecule to store 1 bit data independently, and the density for data storage can be greatly enhanced. When the bilayer exhibits intralayer ferromagnetism and interlayer antiferromagnetic coupling, a considerable difference in Curie temperature between 2 layers and a switchable net magnetization can be formed due to the vertical polarization. At a certain range of temperature, the exchange of paramagnetic-ferromagnetic phases between 2 layers is accompanied by ferroelectric switching, leading to a hitherto unreported type of multiferroic coupling that is long-sought for efficient "magnetic reading + electric writing".
近年来，具有超低开关势垒的独特滑动铁电机制已在一系列二维（2D）材料中得到实验验证。然而，其实际应用受到低极化、特定堆叠构型中铁电相合成的挑战以及数据存储密度低的阻碍，因为开关过程涉及整个层的大面积同时滑动。在此，通过第一性原理计算，我们提出了一种插层在二维双层中的单金属卟啉分子中的半滑动铁电现象。可以形成与堆叠构型无关的增强垂直极化，并通过分子滑动伴随着其金属离子从上层到下层的垂直位移来切换。这种半滑动铁电现象使每个分子能够独立存储1位数据，并且可以大大提高数据存储密度。当双层表现出层内铁磁性和层间反铁磁耦合时，由于垂直极化，两层之间会形成相当大的居里温度差异和可切换的净磁化强度。在一定温度范围内，两层之间顺磁 - 铁磁相的转变伴随着铁电开关，导致一种迄今未报道的多铁性耦合类型，这是长期以来寻求的高效“磁读 + 电写”方式。
