| Project/Area Number |
21J12607
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| Research Category |
Grant-in-Aid for JSPS Fellows
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| Allocation Type | Single-year Grants |
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| Section | 国内 |
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| Review Section |
Basic Section 26040:Structural materials and functional materials-related
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| Research Institution | Kyushu University |
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Principal Investigator |
LEE SUJIN 九州大学, 工学府, 特別研究員(DC2)
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| Project Period (FY) |
2021-04-28 – 2023-03-31
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| Project Status |
Completed (Fiscal Year 2022)
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| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2022: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2021: ¥800,000 (Direct Cost: ¥800,000)
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| Keywords | electron holography / demagnetization field / Nd-Fe-B magnet / TEM / coercivity / permanent magnet / phase shift / 3D magnetic simulation |
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| Outline of Research at the Start |
透過電子顕微鏡法の一種である電子線ホログラフィーを高度化し、磁石材料内部の反磁場の分布を明らかにすることを目的とする。従来、電子線ホログラフィーの観察対象は「磁束」、即ち磁化と磁場（試料内の反磁場や、試料外の漏洩磁場）が加算されたものに制限されていた。本研究では、透過電子顕微鏡法で決定した結晶方位（磁化容易軸の方向）や試料形態、ならびに三次元磁場分布の計算結果を参照して、磁化由来の成分と、反磁場由来の成分を分離する技術の基盤を整備する。
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| Outline of Annual Research Achievements |
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.
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| Research Progress Status |
令和4年度が最終年度であるため、記入しない。
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| Strategy for Future Research Activity |
令和4年度が最終年度であるため、記入しない。
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