Song Dongsheng, Zheng Fengshan, Dunin-Borkowski Rafal E
Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China; Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich 52425, Germany.
Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich 52425, Germany.
Ultramicroscopy. 2022 Apr;234:113476. doi: 10.1016/j.ultramic.2022.113476. Epub 2022 Jan 26.
Two-dimensional (2D) van der Waals magnets have drawn considerable attention in recent years triggered by the huge interest in novel magnetism and spintronic devices. Magnetic measurement of 2D van der Waals (vdW) magnets is crucial to understand the physical origin of magnetism in 2D limits. Therefore, advanced magnetic characterization techniques are highly required. However, only a limited number of such techniques are available due to the extremely small volume of 2D vdW magnets. Here, we introduce the electron magnetic chiral dichroism (EMCD) technique in transmission electron microscope (TEM) to measure 2D vdW crystals. In comparison with some other already-employed techniques in 2D magnets, EMCD is able to quantitatively measure magnetic parameters in three orthogonal directions at nanometer or even at atomic scale. We then perform EMCD simulations on several typical 2D vdW magnets with respect to the accelerating voltage, the number of atomic layers and beam tilt under zone axial orientation. The intensity and distribution of EMCD signals in three orthogonal directions are given in the diffraction plane, thereby providing an optimized design to achieve EMCD measurements. Finally, we discuss the signal-to-noise-ratio and required electron dose in order to obtain a measurable EMCD signal for 2D vdW magnets. Our results provide a feasibility analysis and guideline to measure 2D vdW magnets in future experiments.
近年来，二维（2D）范德华磁体因其在新型磁性和自旋电子器件方面的巨大吸引力而备受关注。二维范德华磁体的磁性测量对于理解二维极限下磁性的物理起源至关重要。因此，迫切需要先进的磁性表征技术。然而，由于二维范德华磁体的体积极小，可用的此类技术数量有限。在此，我们介绍了透射电子显微镜（TEM）中的电子磁手性二色性（EMCD）技术来测量二维范德华晶体。与二维磁体中已采用的其他一些技术相比，EMCD能够在纳米甚至原子尺度上定量测量三个正交方向的磁性参数。然后，我们针对区域轴取向，对几种典型的二维范德华磁体在加速电压、原子层数和束倾斜度方面进行了EMCD模拟。在衍射平面中给出了三个正交方向上EMCD信号的强度和分布，从而提供了一种优化设计以实现EMCD测量。最后，我们讨论了信噪比和所需的电子剂量，以便为二维范德华磁体获得可测量的EMCD信号。我们的结果为未来实验中测量二维范德华磁体提供了可行性分析和指导。
