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116 results on '"Ohtsuka, Masahiro"'

4. Proposal for measuring magnetism with patterned apertures

Author

Negi, Devendra, Spiegelberg, Jakob, Muto, Shunsuke, Thersleff, Thomas, Ohtsuka, Masahiro, Schönström, Linus, Tatsumi, Kazuyoshi, and Rusz, Jaán

Subjects
Condensed Matter - Materials Science
Abstract

We propose a magnetic measurement method utilizing a patterned post-sample aperture in a transmission electron microscope. While utilizing electron magnetic circular dichroism, the method circumvents previous needs to shape the electron probe to an electron vortex beam or astigmatic beam. The method can be implemented in standard scanning transmission electron microscopes by replacing the spectrometer entrance aperture with a specially shaped aperture, hereafter called ventilator aperture. The proposed setup is expected to work across the whole range of beam sizes -- from wide parallel beams down to atomic resolution magnetic spectrum imaging., Comment: 6 pages, 4 figures

Published
2018
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11. A study on the relationship of magnetic moments orientation in L10FePt network nanostructured film by electron energy-loss magnetic chiral dichroism using semi-core excitation spectra

Author

Makino, Hitoshi, Rusz, Jan, Wang, Jian, Turenne, Diego, Ohtsuka, Masahiro, Takahashi, Yukiko K., Dürr, Hermann, Muto, Shunsuke, Makino, Hitoshi, Rusz, Jan, Wang, Jian, Turenne, Diego, Ohtsuka, Masahiro, Takahashi, Yukiko K., Dürr, Hermann, and Muto, Shunsuke

Abstract

In this study, we applied electron energy-loss magnetic chiral dichmism (EMCD), an electron counterpart of X-ray magnetic circular dichmism (XMCD), to a network nanostructured FePt L1(0) ordered alloy film to examine the relative orientation of magnetic moments between neighboring Fe and Pt atoms using the Fe-M-2,M-3, Pt-O-2,O-3, and Pt-N-6,N-7 semi-core excitation spectra with transmission electron microscopy and electron energy-loss spectroscopy. EMCD signals were successfully extracted from a large number of spectra using a dedicated data analysis procedure to obtain sufficient noise statistics. Results showed that the relative sign relation of the EMCD signals between the Fe and Pt absorption edges was consistent with that of the theoretical dielectric tensor while assuming that parallel magnetic moments exist between neighboring Fe and Pt. We believe the results of this study can be applied to alloys with different nanostructures to determine whether the spin configuration depends on the size and geometry of the nanostructures.

Published
2022
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19. Proposal for Measuring Magnetism with Patterned Apertures in a Transmission Electron Microscope

Author

Negi, Devendra Singh, Spiegelberg, Jakob, Muto, Shunsuke, Thersleff, Thomas, Ohtsuka, Masahiro, Schonstrom, Linus, Tatsumi, Kazuyoshi, Rusz, Jan, Negi, Devendra Singh, Spiegelberg, Jakob, Muto, Shunsuke, Thersleff, Thomas, Ohtsuka, Masahiro, Schonstrom, Linus, Tatsumi, Kazuyoshi, and Rusz, Jan

Abstract

We propose a magnetic measurement method utilizing a patterned postsample aperture in a transmission electron microscope. While utilizing electron magnetic circular dichroism, the method circumvents previous needs to shape the electron probe to an electron vortex beam or astigmatic beam. The method can be implemented in standard scanning transmission electron microscopes by replacing the spectrometer entrance aperture with a specially shaped aperture, hereafter called a ventilator aperture. The proposed setup is expected to work across the whole range of beam sizes-from wide parallel beams down to atomic resolution magnetic spectrum imaging.

Published
2019
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22. Unmixing hyperspectral data by using signal subspace sampling

Author

Spiegelberg, Jakob, Muto, Shunsuke, Ohtsuka, Masahiro, Pelckmans, Kristiaan, Rusz, Jan, Spiegelberg, Jakob, Muto, Shunsuke, Ohtsuka, Masahiro, Pelckmans, Kristiaan, and Rusz, Jan

Abstract

This paper demonstrates how Signal Subspace Sampling (SSS) is an effective pre-processing step for Non-negative Matrix Factorization (NMF) or Vertex Component Analysis (VCA). The approach allows to uniquely extract non-negative source signals which are orthogonal in at least one observation channel, respectively. It is thus well suited for processing hyperspectral images from X-ray microscopy, or other emission spectroscopies, into its non-negative source components. The key idea is to resample the given data so as to satisfy better the necessity and sufficiency conditions for the subsequent NMF or VCA. Results obtained both on an artificial simulation study as well as based on experimental data from electronmicroscopy are reported.

Published
2017
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23. Localization of magnetic circular dichroic spectra in transmission electron microscopy experiments with atomic plane resolution

Author

Rusz, Ján, Spiegelberg, Jakob, Muto, Shunsuke, Thersleff, Thomas, Ohtsuka, Masahiro, Leifer, Klaus, Oppeneer, Peter M., Rusz, Ján, Spiegelberg, Jakob, Muto, Shunsuke, Thersleff, Thomas, Ohtsuka, Masahiro, Leifer, Klaus, and Oppeneer, Peter M.

Abstract

Inelastic electron scattering is a consequence of mostly Coulomb interaction between electrons in the sample and electron beam and, as such, it is a nonlocal event. In atomic resolution experiments, it thus opens the following question: How far is the origin of the inelastic scattering signal that is observed when the electron beam is passing nearby an atomic column or plane? We analyze computationally the delocalization of the magnetic signal in electron magnetic circular dichroism (EMCD) experiments in the so-called three-beam orientation, allowing one to image individual atomic planes. We compare the classical EMCD setup using the double-difference procedure (DD-EMCD) to a recently introduced atomic plane resolution EMCD (APR-EMCD) geometry, assuming the same probe size. We observe a strong localization of the EMCD signal to the closest atomic plane, confirming the potential of EMCD to study an evolution of magnetic properties near surfaces or interfaces with atomic plane resolution. The localization of the EMCD signal is remarkably higher than the localization of the nonmagnetic component of the inelastic scattering cross section. We also analyze double-channeling effects and find them particularly strong for the DD-EMCD method, while for APR-EMCD they appear to be minor. The DD-EMCD signal, on the other hand, appears to be more robust with respect to sample thickness than that of the APR-EMCD.

Published
2017
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48. Effect of convergent beam semiangle on image intensity in HAADF STEM images.

Author

Kuramochi, Koji, Kotaka, Yasutoshi, Yamazaki, Takashi, Ohtsuka, Masahiro, Hashimoto, Iwao, and Watanabe, Kazuto

Subjects
IMAGE, SCANNING transmission electron microscopy, SPHERICAL aberration, OPTICS, ATOMS, OPTICAL instruments
Abstract

In this study, we experimentally and theoretically show that the intensities of bright spots in a spherical aberration (Cs)-uncorrected high-angle annular darkfield (HAADF) scanning transmission electron microscope (STEM) image of [011]-oriented Co3O4, which has two different numbers of Co atoms in the projected atomic columns, are reversed with increasing sample thickness. However, Cs-corrected HAADF STEM images produce intensities that correctly depend on the average number of atoms in the projected atomic columns. From an analysis based on the Bloch-wave theorem, it is found that an insufficient semiangle of the incident convergent beam yields intensities that do not depend on the average atomic number in the atomic columns. [ABSTRACT FROM AUTHOR]

Published
2010
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49. Comparison of Interface Characterization between Ag(In,Ga)Se2 and Cu(In,Ga)Se2 Solar Cells by High-Angle-Annular Dark-Field Scanning Transmission Electron Microscopy

Author

Xianfeng, Zhang, Kobayashi, Tsuyoshi, Kurokawa, Yasuyoshi, Tashiro, Yoshiyuki, Ohtsuka, Masahiro, Yamada, Tomoyuki, and Yamada, Akira

Abstract

The interface of Ag(In,Ga)Se2(AIGS) and Cu(In,Ga)Se2(CIGS) solar cells was investigated by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging method. It was found from the results that the AIGS film had Ag-rich and Ag-poor layers. The CdS layer in the CIGS solar cell had a denser structure and a better connection with the CIGS layer than the CdS layer in the AIGS solar cell. The lattice between CIGS and CdS was continuous and ordered. However, there were some defects in CdS and the lattice arrangement was distorted at the AIGS/CdS interface in the AIGS solar cell, resulting in the poor performance of the AIGS solar cell compared with the CIGS solar cell.

Published
2011
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