Unveiling the impact of temperature on magnon diffuse scattering detection in the transmission electron microscope
Unveiling the impact of temperature on magnon diffuse scattering detection in the transmission electron microscope
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DOI：
10.1103/physrevb.108.134435
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发表时间：
2023-02
影响因子：
3.7
通讯作者：
J. '. Castellanos-Reyes;Paul M. Zeiger;Anders Bergman;D. Kepaptsoglou;Q. Ramasse;J. Idrobo;Ján Rusz
中科院分区：
文献类型：
--
作者：
J. '. Castellanos-Reyes;Paul M. Zeiger;Anders Bergman;D. Kepaptsoglou;Q. Ramasse;J. Idrobo;Ján Rusz
随着电子能量损失谱技术的发展，磁振子扩散散射（MDS）信号在扫描透射电子显微镜（STEM）中具有高空间分辨率。然而，在STEM中检测MDS信号具有挑战性，因为它们与更强的热漫反射（TDS）信号重叠。在300 K的bcc Fe中，大于或与TDS信号相当的MDS信号出现在中央布拉格盘下，进入目前无法进入的能量损失区。因此，要检测STEM中的MDS，需要找到TDS和MDS信号可以分离的条件。由于磁振子和声子信号的不同热特征，温度可能是一个关键因素。在这项工作中，我们提出了一项研究温度对bcc Fe中MDS和TDS的影响-考虑到中央布拉格盘外的探测器和固定的收敛电子探针-使用冷冻声子和冷冻磁振子多片方法。我们的研究表明，忽略原子振动的影响会导致MDS信号在铁的居里温度之前近似线性增长，之后它表现出较小的变化。由于动态衍射的作用，MDS信号呈现出一种交替的行为，而不是作为厚度的函数单调增加。包括原子振动通过复杂原子静电势的影响，导致MDS信号的线性增长转变为非线性行为，在1100 K时，样品厚度为16.072 nm时显示出主导峰。相比之下，TDS信号比MDS信号线性增长，但仍然表现出明显的动态衍射效应。信噪比（SNR）分析表明，在可实现的测量条件和采集次数下，MDS信号对总散射强度的贡献具有统计学意义。
Magnon diffuse scattering (MDS) signals could be studied with high spatial resolution in scanning transmission electron microscopy (STEM), thanks to recent technological progress in electron energy loss spectroscopy. However, detecting MDS signals in STEM is challenging due to their overlap with stronger thermal diffuse scattering (TDS) signals. In bcc Fe at 300 K, MDS signals greater than or comparable to TDS signals occur under the central Bragg disk, into a currently inaccesible energy-loss region. Therefore, to detect MDS in STEM, it is necessary to find conditions in which TDS and MDS signals can be separated. Temperature may be a key factor due to the distinct thermal signatures of magnon and phonon signals. In this work, we present a study on the effects of temperature on MDS and TDS in bcc Fe -- considering a detector outside the central Bragg disk and a fixed convergent electron probe -- using the frozen phonon and frozen magnon multislice methods. Our study reveals that neglecting the effects of atomic vibrations causes the MDS signal to grow approximately linearly up to the Curie temperature of Fe, after which it exhibits less variation. The MDS signal displays an alternating behavior due to dynamical diffraction, instead of increasing monotonically as a function of thickness. Including the effects of atomic vibrations through a complex atomic electrostatic potential causes the linear growth of the MDS signal to change to a non-linear behavior that exhibits a predominant peak for a sample of thickness 16.072 nm at 1100 K. In contrast, the TDS signal grows more linearly than the MDS signal but still exhibits appreciable dynamical diffraction effects. An analysis of the signal-to-noise ratio (SNR) shows that the MDS signal can be a statistically significant contribution to the total scattering intensity under realizable measurement conditions and acquisition times.