電子線ホログラフィーによる磁場解析の高度化と磁石材料への応用

电子束全息磁场分析的进展及其在磁性材料中的应用

• 批准号: 21J12607
• 负责人: LEE SUJIN
• 金额: $ 0.96万
• 依托单位: Kyushu University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for JSPS Fellows
• 财政年份: 2021
• 资助国家: 日本
• 起止时间: 2021-04-28 至 2023-03-31
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-21J12607/
• 关键词: electron holography; demagnetization field; Nd-Fe-B magnet; TEM; coercivity; permanent magnet; phase shift; 3D magnetic simulation

We established a new method that extracts the demagnetization field from electron holography observation (i.e., reconstructed phase image) in the last fiscal year. In the next step, to prove the validity of the method, we applied it to a real thin-foiled singlecrystalline Nd2Fe14B specimen with a parallelepiped shape. As a result, the demagnetization field could be observed within the specimen. Furthermore, the result of demagnetization field in this research agrees with the simulation based on micromagnetic theory showing the accuracy of <0.065 T (Tesla). The method can be applied to a permanent magnet and help with the understanding on the coercivity mechanism. The achievements were published in Microscopy in November 2022.The other subject is the precision improvement of phase-shift analysis on a Nd-Fe-B thin foil that causes a poor contrast of electron hologram because of consisting of heavy element (i.e., Nd element). The electron holograms with a poor contrast produces the undesired phase discontinuities during the process of phase retrieval. For this purpose, we carried out the noise reduction of electron hologram observations with the the wavelet hidden Markov model (WHMM) that can distinguish the signal even weaker than the noise. Consequently, it was demonstrated that the noise reduction using WHMM was effective for suppressing the unwanted discontinuity. The denoising with WHMM can be helpful to improve the precision in the analysis of demagnetization field deduced from the method in this research.

我们建立了一种从上一财年的电子全息观测（即重构相像）中提取退磁场的新方法。下一步，为了证明该方法的有效性，我们将其应用于具有平行六面体形状的真实薄箔单晶Nd2Fe14B试样。因此，可以观察到试样内部的退磁场。此外，本研究的退磁场计算结果与基于微磁理论的仿真结果一致，精度<0.065 T （Tesla）。该方法适用于永磁体，有助于对矫顽力机理的理解。这一成果于2022年11月发表在《显微镜》杂志上。另一个课题是对Nd- fe - b薄片进行相移分析的精度改进，该薄片由于含有重元素（即Nd元素）而导致电子全息图对比度差。对比度差的电子全息图在相位恢复过程中会产生不希望出现的相位不连续现象。为此，我们利用小波隐马尔可夫模型（WHMM）对电子全息图观测进行降噪，该模型能分辨出比噪声更弱的信号。结果表明，利用WHMM进行降噪可以有效地抑制不需要的不连续性。利用WHMM去噪有助于提高该方法推导出的退磁场分析精度。

项目成果

Observation of demagnetization field within thin-foiled Nd-Fe-B magnet by using electron holography

电子全息观测薄箔Nd-Fe-B磁体内部退磁场

• 发表时间: 2022
• 作者: Huang Xin;Guo Yangyu;Wu Yunhui;Masubuchi Satoru;Watanabe Kenji;Taniguchi Takashi;Zhang Zhongwei;Volz Sebastian;Machida Tomoki;Nomura Masahiro;木村遥;白那日蘇;LEE SUJIN
• 通讯作者: LEE SUJIN

Extraction of Phase Information Approximating the Demagnetization Field within a Thin-foiled Magnet Using Electron Holography Observation

使用电子全息观测提取近似薄箔磁体内退磁场的相位信息

• DOI: 10.1093/jmicro/dfac066
• 发表时间: 2023
• 期刊: Microscopy
• 影响因子: 1.8
• 作者: S. Lee;A. Sato;T. Tamaoka;K. Yubuta;M. Auchi;T. Sasaki;T. Ohkubo;K. Hono;Y. Murakami
• 通讯作者: Y. Murakami

Observation of demagnetization field within thin-foiled Nd-Fe-B magnet by using electron holography

电子全息观测薄箔Nd-Fe-B磁体内部退磁场

• 发表时间: 2022
• 作者: Sujin Lee;Atsuko Sato;Takehiro Tamaoka;Kunio Yubuta;Mitsunari Auchi;Yasukazu Murakami
• 通讯作者: Yasukazu Murakami

Extraction of phase information about demagnetization field using electron holography observation

利用电子全息观测提取退磁场相位信息

• 发表时间: 2022
• 作者: Sujin LEE;Atsuko Sato;Takehiro Tamaoka;Kunio Yubuta;Mitsunari Auchi;Yasukazu Murakami
• 通讯作者: Yasukazu Murakami