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219 results on '"Saitoh Koh"'

3. Slow dynamics of disordered zigzag chain molecules in layered LiVS2 under electron irradiation

Author

Katayama, Naoyuki, Kojima, Keita, Yamaguchi, Tomoki, Hattori, Sosuke, Tamura, Shinya, Ohara, Koji, Kobayashi, Shintaro, Sugimoto, Koudai, Ohta, Yukinori, Saitoh, Koh, and Sawa, Hiroshi

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Electronic instabilities in transition metal compounds often spontaneously form orbital molecules, which consist of orbital-coupled metal ions at low temperature. Recent local structural studies utilizing the pair distribution function revealed that preformed orbital molecules appear disordered even in the high-temperature paramagnetic phase. However, it is unclear whether preformed orbital molecules are dynamic or static. Here, we provide clear experimental evidence of the slow dynamics of disordered orbital molecules realized in the high-temperature paramagnetic phase of LiVS2, which exhibits vanadium trimerization upon cooling below 314 K. Unexpectedly, the preformed orbital molecules appear as a disordered zigzag chain that fluctuate in both time and space under electron irradiation. Our findings should advance studies on soft matter physics realized in an inorganic material due to disordered orbital molecules., Comment: 17 pages, 4 figures and supplemental information

Published
2021
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4. Giant impurity effect on anomalous Hall effect of Mn3Sn.

Author

Yano, Rikizo, Kihara, Shunya, Yoneda, Masayasu, Vu, Huyen Thi Ngoc, Suto, Hiroyuki, Katayama, Naoyuki, Yamaguchi, Takeo, Kuwahara, Makoto, Suzuki, Michi-To, Saitoh, Koh, and Kashiwaya, Satoshi

Subjects
ANOMALOUS Hall effect, ANTIFERROMAGNETIC materials, CRYSTAL whiskers
Abstract

Mn3Sn is an anomalous Hall effect (AHE) antiferromagnet that exhibits the hysteretic AHE in antiferromagnetic (AFM) phase at room temperature. We report that whisker Mn3Sn crystals grown by the flux method exhibit a non-hysteretic AHE at mid-to-low temperatures when the whisker Mn3Sn is surrounded by a thin layer of ferromagnetic Mn2−xSn. These crystals exhibit a hysteretic AHE above 275 K due to the spin alignment of the inverse triangular lattice, which is similar to other crystals. However, upon cooling the crystal, it exhibits a non-hysteretic AHE with a spiral AFM spin structure at 100–200 K. We concluded that the non-hysteretic AHE is induced at the interface of Mn2−xSn/Mn3Sn. We believe that the scalar-spin chirality in the spiral AFM phase of Mn3Sn, modulated by Mn2−xSn through the magnetic proximity effect, produces the AHE. This discovery opens a new avenue for tailoring the AHE by magnetic layers. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Observation of domain wall bimerons in chiral magnets

Author

Nagase, Tomoki, So, Yeong-Gi, Yasui, Hayata, Ishida, Takafumi, Yoshida, Hiroyuki K., Tanaka, Yukio, Saitoh, Koh, Ikarashi, Nobuyuki, Kawaguchi, Yuki, Kuwahara, Makoto, and Nagao, Masahiro

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Topological defects embedded in or combined with domain walls have been proposed in various systems, some of which are referred to as domain wall skyrmions or domain wall bimerons. However, the experimental observation of such topological defects remains an ongoing challenge. Here, using Lorentz transmission electron microscopy, we report the experimental discovery of domain wall bimerons in chiral magnet Co-Zn-Mn(110) thin films. By applying a magnetic field, multidomain structures develop, and simultaneously, chained and isolated bimerons arise as the localized state between the domains with the opposite in-plane components of net magnetization. The multidomain formation is attributed to magnetic anisotropy and dipolar interaction, and domain wall bimerons are stabilized by the Dzyaloshinskii-Moriya interaction. In addition, micromagnetic simulations show that domain wall bimerons appear for a wide range of conditions in chiral magnets with cubic magnetic anisotropy. Our results promote further study in various fields of physics., Comment: 30 pages, 10 figures (including Supplementary Materials)

Published
2020
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6. Giant impurity effect on anomalous Hall effect of Mn3Sn

Author

Yano, Rikizo, primary, Kihara, Shunya, additional, Yoneda, Masayasu, additional, Vu, Huyen Thi Ngoc, additional, Suto, Hiroyuki, additional, Katayama, Naoyuki, additional, Yamaguchi, Takeo, additional, Kuwahara, Makoto, additional, Suzuki, Michi-To, additional, Saitoh, Koh, additional, and Kashiwaya, Satoshi, additional

Published
2024
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8. Measuring the orbital angular momentum of electron vortex beams using a forked grating

Author

Saitoh, Koh, Hasegawa, Yuya, Hirakawa, Kazuma, Tanaka, Nobuo, and Uchida, Masaya

Subjects
Quantum Physics
Abstract

The present study experimentally examines how an electron vortex beam with orbital angular momentum (OAM) undergoes diffraction through a forked grating. The nth-order diffracted electron vortex beam after passing through a forked grating with a Burgers vector of 1 shows an OAM transfer of nh. Hence, the diffraction patterns become mirror asymmetric owing to the size difference between the electron beams. Such a forked grating, when used in combination with a pinhole located at the diffraction plane, could act as an analyzer to measure the OAM of input electrons., Comment: 5 pages, 3 figures

Published
2013
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22. Kuwahara et al. Reply

Author

Kuwahara, Makoto, primary, Yoshida, Yuya, additional, Nagata, Wataru, additional, Nakakura, Kojiro, additional, Furui, Masato, additional, Ishida, Takafumi, additional, Saitoh, Koh, additional, Ujihara, Toru, additional, and Tanaka, Nobuo, additional

Published
2021
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23. Intensity Interference in a Coherent Spin-Polarized Electron Beam

Author

Kuwahara, Makoto, Yoshida, Yuya, Nagata, Wataru, Nakakura, Kojiro, Furui, Masato, Ishida, Takafumi, Saitoh, Koh, Ujihara, Toru, Tanaka, Nobuo, Kuwahara, Makoto, Yoshida, Yuya, Nagata, Wataru, Nakakura, Kojiro, Furui, Masato, Ishida, Takafumi, Saitoh, Koh, Ujihara, Toru, and Tanaka, Nobuo

Abstract

We investigate the intensity interference between pairs of electrons using a spin-polarized electron beam having a high polarization and a narrow energy width. We observe spin-dependent antibunching on the basis of coincident counts of electron pairs performed with a spin-polarized transmission electron microscope, which could control the spin-polarization without any changes in the electron optics. The experimental results show that the time correlation was only affected by the spin polarization, demonstrating that the antibunching is associated with fermionic statistics. The coherent spin-polarized electron beam facilitates the extraction of intrinsic quantum interference.

Published
2021

42. Denoising of series electron holograms using tensor decomposition.

Author

Nomura, Yuki, Yamamoto, Kazuo, Anada, Satoshi, Hirayama, Tsukasa, Igaki, Emiko, and Saitoh, Koh

Subjects
ELECTRON holography, HOLOGRAPHY, P-N junctions (Semiconductors), SIGNAL-to-noise ratio, ELECTRONS
Abstract

In this study, a noise-reduction technique for series low-dose electron holograms using tensor decomposition is demonstrated through simulation. We treated an entire dataset of the series holograms with Poisson noise as a third-order tensor, which is a stack of 2D holograms. The third-order tensor, which is decomposed into a core tensor and three factor matrices, is approximated as a lower-rank tensor using only noise-free principal components. This technique is applied to simulated holograms by assuming a p-n junction in a semiconductor sample. The peak signal-to-noise ratios of the holograms and the reconstructed phase maps have been improved significantly using tensor decomposition. Moreover, the proposed method was applied to a more practical situation of time-resolved in situ electron holography by considering a nonuniform fringe contrast and fringe drift relative to the sample. The accuracy and precision of the reconstructed phase maps were quantitatively evaluated to demonstrate its effectiveness for in situ experiments and low-dose experiments on beam-sensitive materials. [ABSTRACT FROM AUTHOR]

Published
2021
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43. Performance of a silicon-on-insulator direct electron detector in a low-voltage transmission electron microscope.

Author

Ishida, Takafumi, Shinozaki, Akira, Kuwahara, Makoto, Miyoshi, Toshinobu, Saitoh, Koh, and Arai, Yasuo

Subjects
TRANSFER functions, ELECTRON detection, DETECTORS, QUANTUM efficiency, ELECTRONS
Abstract

The performance of a direct electron detector using silicon-on-insulator (SOI) technology in a low-voltage transmission electron microscope (LVTEM) is evaluated. The modulation transfer function and detective quantum efficiency of the detector are measured under backside illumination. The SOI-type detector is demonstrated to have high sensitivity and high efficiency for the direct detection of low-energy electrons. The detector is thus considered suitable for low-dose imaging in an LVTEM. [ABSTRACT FROM AUTHOR]

Published
2021
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