氯化铬二维磁性的表征、调控与器件应用研究

The recently discovered two-dimensional (2D) ferromagnetism in layered van der Waals (vdW) crystals has created new opportunities for exploring 2D magnetism and novel functional devices. So far, most of the reported 2D magnetic materials possess out-of-plane anisotropy with the spin orientation perpendicular to the layer, which limits both the observation of many interesting quantum mechanical phenomena and some magnetic device applications. Layered magnetic insulator CrCl3 with in-plane magnetization is expected to solve this problem, but the experimental study of the atomically thin CrCl3 still remains elusive. Recently, we have established the magnetic structure of the 2D magnet CrI3 and fabricated magnetic tunnel junction (MTJ) devices with extremely large magnetoresistance accordingly. We next prepared the MTJ device based on bilayer CrCl3 and get some preliminary results about its magnetic properties. In this project, we propose to use the magneto-transport technique to systematically explore the magnetic structure and phase transitions of 2D CrCl3, realizing the control of its magnetization with the magnetic field, the electric field and/or the light illumination. We will fabricate 2D heterostructures with CrCl3 to explore the proximity effect induced interaction between the in-plane magnetization and the superconductivity, the topological surface state and so on, revealing new physics and new phenomena at the interface. We will design and engineer novel magneto-electronic devices based on CrCl3, such as the MTJ and the spin transfer torque devices. We aim to achieve low power-consumption, tunable and integrated devices and provide fundamental support for applications.

层状范德华晶体中观测到的二维铁磁性为低维磁性的研究与磁电器件的开发提供了新的机遇。已知的二维磁性材料大都具有面外磁各向异性，其磁化垂直于层面，限制了很多新奇量子现象的观测与器件应用。二维材料三氯化铬（CrCl3）具有面内铁磁极化，有望解决这一问题，然而关于原子级别厚度CrCl3磁性的研究还鲜有报道。申请人曾系统表征二维磁性材料三碘化铬（CrI3）的磁结构，并据此制备了高性能磁隧道结器件。最近，申请人又首次制备了基于双层CrCl3的磁隧道结，初步探索了其磁学特性。本项目拟通过电输运测量技术等，系统研究二维CrCl3的磁结构、磁相变等性质，实现磁场、电场等对其磁化的调控；制备CrCl3二维异质结结构，探索面内二维铁磁性通过近邻效应与拓扑表面态、超导态等的相互作用，发现新物理、新现象；设计基于CrCl3的磁隧道结、自旋转矩存储单元等低功耗、易调控的磁电子器件，为实际应用提供原理性支持。

层状范德华晶体中观测到的二维铁磁性为低维磁性的研究与高性能自旋电子器件的开发提供了新的机遇。已知的二维磁性材料大都具有面外磁各向异性，其磁化垂直于层面，限制了很多新奇量子现象的观测与器件应用。三氯化铬（CrCl3）具有面内铁磁极化，有望解决这一问题，然而关于原子级别厚度CrCl3及相关异质结的研究还鲜有报道。本项目针对CrCl3及与之相关的低维量子材料和异质结结构，从以下几个方面展开研究：1.二维CrCl3的磁学特性表征与调控；2.基于CrCl3等二维磁性材料的异质结制备与界面效应观测；3.基于CrCl3等新型二维量子材料及其异质结构的原型电子器件构筑。通过低温量子输运、显微光电响应等实验技术，结合理论分析与计算，项目取得了以下主要成果：1.构筑了基于少层CrCl3的隧穿异质结，观测到其中存在的自旋过滤效应，并通过隧穿电流的测量表征了少层CrCl3的磁结构、磁相变，尤其是实现了对少层CrCl3面内磁各向异性的有效观测；2.构筑了基于少层CrCl3、CrI3等新型范德华磁性材料的自旋过滤磁隧道结原型器件，其磁阻率等主要性能参数相比传统磁隧道结器件获得大幅提升；3.利用CrCl3、Cr5Te8等低维磁性材料与其它范德华量子材料构筑了多种磁性异质结，并成功制备了一种二维磁性摩尔超晶格结构，为后续利用超晶格对异质结界面自旋极化电子的能带和量子态等进行人工调控提供了可能；4.制备了基于二维超导材料NbSe2的新型光探测原型器件，其在可见光波段的响应率可达42.3A/W，并进一步构筑了NbSe2-石墨烯、NbSe2-二维磁性材料-石墨烯等二维异质结光探测器，实现栅极电压对超导光电流的调控。通过项目实施，在包括ACS Nano等权威期刊发表受本项目资助的SCI论文3篇，公布发明专利1项，培养毕业研究生1名，在读研究生5名。

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