Evolution of interlayer and intralayer magnetism in three atomically thin chromium trihalides
Evolution of interlayer and intralayer magnetism in three atomically thin chromium trihalides
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三种原子薄三卤化铬层间和层内磁性的演变
DOI：
10.1073/pnas.1902100116
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发表时间：
2019-06-04
影响因子：
11.1
通讯作者：
Tsen, Adam W.
中科院分区：
文献类型：
--
作者：
Kim, Hyun Ho;Yang, Bowen;Tsen, Adam W.
二维磁性半导体如CrI3是一类新的范德华材料，可能允许开发新的二维自旋电子器件。虽然CrI3层内的强磁各向异性将铁磁性稳定到单层，但层之间的弱反铁磁性耦合会产生极大的隧道磁阻。我们使用隧道和磁光测量的组合来研究整个二维三卤化铬家族（CrX3, X = I, Br, Cl）。我们的研究结果阐明了这三种材料的层间耦合和层内自旋哈密顿量，并进一步证明了铁磁性可以在单层CrBr3和双层CrCl3中稳定，而没有强的各向异性。我们对三种不同的磁性半导体，cr3， CrBr3和CrCl3进行了全面的研究，通过在范德华隧道结中结合少层和双层样品。我们发现层间磁有序、交换间隙、磁各向异性和磁振子激发随卤素原子的变化而有系统地演化。通过拟合解释最近邻交换相互作用的自旋波理论，我们能够进一步确定描述所有三个系统的简单自旋哈密顿量。这些结果将二维磁性平台扩展到单一材料家族中的Ising， Heisenberg和XY自旋类。通过磁光测量，我们还证明了铁磁性可以在各向同性的CrBr3中稳定到单层，而转变温度仍然接近体的温度。
Significance Two-dimensional magnetic semiconductors such as CrI3 are a new class of van der Waals material that may allow for the development of novel 2D spintronic devices. While strong magnetic anisotropy within the CrI3 layers stabilizes ferromagnetism down to a monolayer, weak antiferromagnetic coupling between the layers gives rise to extremely large tunnel magnetoresistance. We use a combination of tunneling and magneto-optical measurements to investigate the entire 2D chromium trihalide family (CrX3, X = I, Br, Cl). Our results elucidate both the interlayer coupling and intralayer spin Hamiltonian for all three materials, and further demonstrate that ferromagnetism can be stabilized in monolayer CrBr3 and bilayer CrCl3 without strong anisotropy. We conduct a comprehensive study of three different magnetic semiconductors, CrI3, CrBr3, and CrCl3, by incorporating both few-layer and bilayer samples in van der Waals tunnel junctions. We find that the interlayer magnetic ordering, exchange gap, magnetic anisotropy, and magnon excitations evolve systematically with changing halogen atom. By fitting to a spin wave theory that accounts for nearest-neighbor exchange interactions, we are able to further determine a simple spin Hamiltonian describing all three systems. These results extend the 2D magnetism platform to Ising, Heisenberg, and XY spin classes in a single material family. Using magneto-optical measurements, we additionally demonstrate that ferromagnetism can be stabilized down to monolayer in more isotropic CrBr3, with transition temperature still close to that of the bulk.