二维磁性材料CuCrP2S6的拉曼特性

Topological Kondo Insulator and Its Transport Propertiy

易康源

11749025

硕士

物理学

陈远珍

2019-05-14

2019-07-11

哈尔滨工业大学

深圳

低维度上的磁性存在着许多有趣的物理学性质，这些可能的新奇特性已在理论上被讨论了数十年。然而，长期以来，通过实验去验证这些理论所预测的性质是十分困难的，这是由于研究者一直无法获得稳定的低维体系材料。因此，在使用机械剥离的方法成功制备了单层石墨烯后，对各类可能具有磁性的低维维材料的研究得到了科研人员的大量关注。有研究表明，FePS3，Cr2GeTe6，CrI3，VSe2、Fe3GeTe2 和CuCrP2S6中存在着磁序；在CuCrP2S6中，则由于铜阳离子产生的电偶极子排序而可能具有多铁性。这些新型的二维磁体可能用于电气控制和自旋电子器件中，并可能实现创纪录的隧穿磁电阻。本论文工作研究了不同厚度的二维CuCrP2S6材料的变温拉曼光谱，进而分析了厚度和温度等因素对CuCrP2S6二维材料结构的影响。 本文主要内容如下：（1）CuCrP2S6的晶体结构及其在温度变化时的顺磁-反铁磁相变和顺电-反铁电相变。（2）利用化学气相传输法生长高质量的CuCrP2S6单晶，并使用X射线衍射法及能量色散光谱确定样品的成分及结晶质量。（3）通过机械剥离方法获得具有不同厚度的CuCrP2S6薄层样品，并利用光学衬度法和原子力显微镜测量样品厚度。（4）通过原子力显微镜及显微拉曼测量确认了少层CuCrP2S6样品在空气中不稳定。（5）测量不同厚度CuCrP2S6样品的变温拉曼光谱，确定薄层样品的结构相变温度。

Magnetism in lower dimensions hosts interesting physics that has been studied theoretically for many decades. However, experimentally realizing the details of these theoretical predictions has been proven difficult. The reason for this difficulty is that atomically thin yet stable films are hard to obtain. The isolation of monolayer graphene by mechanical exfoliation provided a path for exploring magnetism in two-dimensional van der Waals materials. New research shows that magnetic ordering was observed in FePS3, Cr2GeTe6, CrI3, VSe2 and Fe3GeTe2. In CuCrP2S6, there may be multiferroics since the coexistence of Cu+ site-based dipole ordering. Those two-dimensional magnetic materials can be used to build nanoscale spintronics devices with a very large tunneling magnetoresistance. Our research focuses on the characterization of two-dimensional CuCrP2S6 nanosheets with different thickness by Raman spectroscopy, so that the thickness dependence and temperature dependence of their structure can be studied. The main contents of this research are listed below:（1） The structure of CuCrP2S6 crystal and its resulted magnetic and electronic phase transitions are introduced.（2） CuCrP2S6 single crystals are synthesized by chemical vapor transport. The structure and compositions of the CuCrP2S6 single crystal are characterized by X-ray diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDX).（3） CuCrP2S6 nanosheets with different thickness are exfoliated on silicon substrate. Their thicknesses are determined by optical contrast and Atomic Force Microscopy (AFM).（4） Ambient instability of few-layer CuCrP2S6 are confirmed by Atomic Force Microscopy (AFM) and Raman spectroscopy.（5） A series of variable temperature dependent Raman spectra is taken from few-layer CuCrP2S6 with different thickness. The temperature of the structural phase transition in few-layer CuCrP2S6 is determined.

反铁电 反铁磁 单层CuCrP2S6 拉曼光谱

antiferroelectricity antiferromagnetism CuCrP2S6 monolayer Raman spectroscopy

中文

联合培养

南方科技大学

易康源. 二维磁性材料CuCrP2S6的拉曼特性[D]. 深圳. 哈尔滨工业大学,2019.