| 研究実績の概要 |
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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