Gao Pengfei, Li Xingxing, Yang Jinlong
Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China.
J Phys Chem Lett. 2021 Jul 29;12(29):6847-6851. doi: 10.1021/acs.jpclett.1c01901. Epub 2021 Jul 19.
Room temperature two-dimensional (2D) ferromagnetism is highly desired in practical spintronics applications. Recently, 1T phase CrTe (1T-CrTe) nanosheets with 5 and thicker layers have been successfully synthesized, which all exhibit the properties of ferromagnetic (FM) metals with Curie temperatures around 305 K. However, whether the ferromagnetism therein can be maintained when continuously reducing the nanosheet's thickness to monolayer limit remains unknown. Here, through first-principles calculations, we explore the evolution of magnetic properties of 1 to 6 layer CrTe nanosheets and several interesting points are found: First, unexpectedly, monolayer CrTe prefers a zigzag antiferromagnetic (AFM) state with its energy much lower than that of FM state. Second, in 2 to 4 layer CrTe, both the intralayer and interlayer magnetic coupling are AFM. Last, when the number of layers is equal to or greater than 5, the intralayer and interlayer magnetic coupling become FM. Such highly thickness dependent magnetism provides a new perspective to control the magnetic properties of 2D materials.
室温二维（2D）铁磁性在实际自旋电子学应用中备受期待。最近，已成功合成出具有5层及更厚层数的1T相CrTe（1T - CrTe）纳米片，它们均表现出居里温度约为305 K的铁磁（FM）金属特性。然而，当将纳米片厚度连续减小至单层极限时，其中的铁磁性是否能够保持仍不清楚。在此，通过第一性原理计算，我们探究了1至6层CrTe纳米片的磁性演变，并发现了几个有趣的点：首先，出乎意料的是，单层CrTe倾向于呈锯齿状反铁磁（AFM）态，其能量远低于FM态。其次，在2至4层CrTe中，层内和层间磁耦合均为AFM。最后，当层数等于或大于5时，层内和层间磁耦合变为FM。这种高度依赖厚度的磁性为控制二维材料的磁性提供了一个新的视角。
