Probe and manipulation of magnetism of two-dimensional CrI3 crystal

Abstract

For a long time, it has been generally acknowledged that low-dimensional (lower than three-dimensions) long-range orders cannot stay stable at any finite temperature, because temperature-induced fluctuations can destroy any long-range orders in low-dimensional systems supported by isotropic short-range interactions. However, this theorem requires that the interaction must be short-range and isotropic. In fact, many low-dimensional systems do not meet these two requirements. For example, due to the strong anisotropy in two-dimensional CrI3 crystals, there is a band gap in the magnon spectrum. When the excitation energy from temperature is much lower than the band gap, the magneton cannot be excited by temperature on a large scale, and the long-range magnetic order in the two-dimensional system will not be destroyed. Various methods have been used to characterize the magnetic order in atomically thin CrI3 crystals, and a lot of attempts have been made to manipulate the magnetic structure in the system. Focusing on CrI3, in this article we review the recent studies on growth, magnetic structure measurement and manipulation of two-dimensional magnetic materials, and also discuss the prospects for the next phase of research from the perspectives of basic condensed matter physics research and electronic engineering applications. 长久以来, 人们普遍相信低维(三维以下)长程序无法在任何有限的温度下稳定存在. 这是因为温度带来的热涨落会破坏由各向同性的短程相互作用支撑的低维体系中对称性破缺的有序态. 然而, 这个定理同时要求相互作用是短程且各向同性的. 事实上很多低维体系是不满足这两个限定条件的. 比如二维CrI3晶体中由于强各向异性的存在, 其磁子色散关系中有禁带存在. 当温度值远远低于该禁带宽度时, 磁子无法被温度大规模激发, 该二维体系中的长程磁序也就不会被破坏. 人们已经利用不同的手段对二维原子层厚度CrI3中的磁序进行了表征, 并且做了大量尝试来调控该体系中的磁性结构. 本文主要综述了CrI3二维磁性材料的生长、磁性结构测量和磁性结构调控, 并对下一阶段的工作从基础凝聚态物理研究以及电子工程应用角度做出展望.