The Exploration On Chemical Vapor Synthesis And Magnetic Properties Of Two-dimensional Cr₂Te₃ Nanosheets

Two-dimensional（2D）magnetic materials are expected to be used in the development of basic physics-related theories and play a key role in new technology fields such as 2D spintronics,on-chip optical communications,and quantum computing because of a range of physical properties that are different from those of bulk materials and thin films,as well as ease of electrical control and chemical functionalization.For 2D magnetic materials to be used in real applications,it is essential to find and synthesize the 2D materials freely with excellent magnetic properties such as high Curie temperature（T_C）and stability.As ideal candidates materials for room temperature ferromagnets,chromium-based tellurides have received great attention.This article aims to achieve high-quality and controllable preparation of 2D Cr₂Te₃ nanosheets through chemical vapor deposition（CVD）;on this basis,the magneto-optical Kerr effect（MOKE）and reflective magnetic circular dichroism（RMCD）were used to study the change characteristics of the magnetic properties of the 2D Cr₂Te₃nanosheets with the adjustment of external stress.The main work is as follows:（1）The high-quality and controllable preparation of 2D Cr₂Te₃ nanosheets is realized by the method of atmospheric pressure chemical vapor deposition（APCVD）.By adjusting the growth parameters and conditions,the crystalline quality of Cr₂Te₃ nanosheets and the cleanliness of the substrate were effectively improved,and the tuning of the lateral size of Cr₂Te₃ nanosheets from～5μm to～100μm was achieved,then the crystalline phase of the nanosheets was determined through a series of characterization means（h P20,PDF#71-2245）.（2）Using MOKE and RMCD technique to study the basic magnetic properties of 2D Cr₂Te₃ nanosheets and the changes in magnetic properties under strain.The obvious square hysteresis loops prove the ferromagnetic and single domain characteristics of the 2D nanosheets.Under+0.37%of applied tensile strain,the T_C of Cr₂Te₃ nanosheets has increased significantly.Compared with nanosheet of the similar thickness under no stress,the T_C of Cr₂Te₃ nanosheet with a thickness of～15 nm under tensile stress is increased by～40 K,and the increase is reduced as the thickness increases.But the coercivity（H_C）is greatly reduced under tensile stress,when the thickness is～15 nm,it is only 4%of the unbent nanosheet.Under the external pressure strain of-0.37%,the T_C of the Cr₂Te₃ nanosheets has been greatly reduced.Compared with the material of the similar thickness,the T_C of the Cr₂Te₃ nanosheets with a thickness of～14 nm is reduced by～30 K.However,the H_C still appears to be greatly reduced,it is only 33%of the unbent one when the thickness is～14 nm.The significant change in the magnetic properties under stress indicates that the 2D Cr₂Te₃ nanosheets have high strain-sensitive properties,and their magnetic properties are closely related to the structure and can be effectively controlled by strain.