Wang Naizhou, Tang Huaibao, Shi Mengzhu, Zhang Hui, Zhuo Weizhuang, Liu Dayong, Meng Fanbao, Ma Likuan, Ying Jianjun, Zou Liangjian, Sun Zhe, Chen Xianhui
Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, and Key Laboratory of Strongly Coupled Quantum Matter Physics , University of Science and Technology of China , Hefei 230026 , Anhui , China.
School of Physics and Materials Science , Anhui University , Hefei 230039 , Anhui , China.
J Am Chem Soc. 2019 Oct 30;141(43):17166-17173. doi: 10.1021/jacs.9b06929. Epub 2019 Oct 18.
Magnetism in the two-dimensional limit has become an intriguing topic for exploring new physical phenomena and potential applications. Especially, the two-dimensional magnetism is often associated with novel intrinsic spin fluctuations and versatile electronic structures, which provides vast opportunities in 2D material research. However, it is still challenging to verify candidate materials hosting two-dimensional magnetism, since the prototype systems have to be realized by using mechanical exfoliation or atomic layer deposition. Here, an alternative manipulation of two-dimensional magnetic properties via electrochemical intercalation of organic molecules is reported. Using tetrabutyl ammonium (TBA), we synthesized a (TBA)CrGeTe hybrid superlattice with metallic behavior, and the Curie temperature is significantly increased from 67 K in pristine CrGeTe to 208 K in (TBA)CrGeTe. Moreover, the magnetic easy axis changes from the ⟨001⟩ direction in CrGeTe to the -plane in (TBA)CrGeTe. Theoretical calculations indicate that the drastic increase of the Curie temperature can be attributed to the change of magnetic coupling from a weak superexchange interaction in pristine CrGeTe to a strong double-exchange interaction in (TBA)CrGeTe. These findings are the first demonstration of manipulation of magnetism in magnetic van der Waals materials by means of intercalating organic ions, which can serve as a convenient and efficient approach to explore versatile magnetic and electronic properties in van der Waals crystals.
二维极限下的磁性已成为探索新物理现象和潜在应用的一个有趣话题。特别是，二维磁性通常与新颖的本征自旋涨落和多样的电子结构相关联，这为二维材料研究提供了广阔机遇。然而，验证具有二维磁性的候选材料仍然具有挑战性，因为原型系统必须通过机械剥离或原子层沉积来实现。在此，报道了一种通过有机分子的电化学插层对二维磁性性质进行的替代操控。使用四丁基铵（TBA），我们合成了具有金属行为的（TBA）CrGeTe混合超晶格，其居里温度从原始CrGeTe中的67 K显著提高到（TBA）CrGeTe中的208 K。此外，磁易轴从CrGeTe中的〈001〉方向变为（TBA）CrGeTe中的 - 平面。理论计算表明，居里温度的急剧升高可归因于磁耦合从原始CrGeTe中的弱超交换相互作用变为（TBA）CrGeTe中的强双交换相互作用。这些发现首次证明了通过插入有机离子来操控磁性范德华材料中的磁性，这可以作为一种方便且高效的方法来探索范德华晶体中多样的磁性和电子性质。
