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188 results on '"Tajiri, Hiroo"'

1. Simulations of Surface X-ray Diffraction from a Monolayer 4He Film Adsorbed on Graphite

Author

Kumashita, Atsuki, Tajiri, Hiroo, Yamaguchi, Akira, Usami, Jun, Sumiyama, Akihiko, Yamane, Yu, Suzuki, Masaru, Minoguchi, Tomoki, Sakurai, Yoshiharu, and Fukuyama, Hiroshi

Subjects
Condensed Matter - Other Condensed Matter, Condensed Matter - Materials Science
Abstract

We carried out simulations of crystal truncation rod (CTR) scatterings, i.e., one of the surface X-ray diffraction techniques with atomic resolution, from a monolayer He film adsorbed on graphite. Our simulations reveal that the 00L rod scatterings from the He monolayer exhibit notable intensity modifications for those from a graphite surface in the ranges of approximately L = 0.6 - 1.7 and L = 2.2 - 3.5. The height of the He monolayer from the graphite surface largely affects the CTR scattering profiles, indicating that CTR scatterings have enough sensitivities to determine the surface structure of the various phases in the He layer. In particular, in the incommensurate solid phase, our preliminary experimental data show the intensity modulations that are expected from the present simulations., Comment: 6 pages, 4 figures, to be published in JPS Conf. Proc

Published
2022
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2. Structural Study of Adsorbed Helium Films: New Approach with Synchrotron Radiation X-rays

Author

Yamaguchi, Akira, Tajiri, Hiroo, Kumashita, Atsuki, Usami, Jun, Yamane, Yu, Sumiyama, Akihiko, Suzuki, Masaru, Minoguchi, Tomoki, Sakurai, Yoshiharu, and Fukuyama, Hiroshi

Subjects
Condensed Matter - Other Condensed Matter, Condensed Matter - Materials Science
Abstract

A few atomic layers of helium adsorbed on graphite have been attracting much attention as one of the ideal quantum systems in two dimension. Although previous reports on neutron diffraction have shown fundamental structural information in these systems, there still remain many open questions. Here, we propose surface crystal truncation rod (CTR) scatterings using synchrotron radiation X-rays as a promising method to reveal surface and interface structures of helium films on graphite at temperatures below 2 K, based on the preliminary experimental results on a monolayer of He-4 on a thin graphite. Our estimation on heat generation by X-ray irradiations also suggests that CTR scatterings are applicable to even at system temperatures near 100 mK., Comment: 9 pages, 3 figures, submitted to Journal of Low Temperature Physics

Published
2021
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3. Structural insight using anomalous XRD into Mn2CoAl Heusler alloy films grown by magnetron sputtering, IBAS and MBE techniques

Author

Tajiri, Hiroo, Kumara, Loku Singgappulige Rosantha, Sakuraba, Yuya, Chen, Zixi, Wang, Jian, Zhou, Weinan, Varun, Kushwaha, Ueda, Kenji, Yamada, Shinya, Hamaya, Kohei, and Hono, Kazuhiro

Subjects
Condensed Matter - Materials Science
Abstract

Inverse Heusler alloy Mn2CoAl thin films, known as a spin-gapless semiconductor (SGS), grown by three different methods: ultra-high vacuum magnetron spattering, Ar-ion beam assisted sputtering, and molecular beam epitaxy, are investigated by comparing their electric transport properties, microstructures and atomic-level structures. Of the samples, the Mn2CoAl thin film grown by MBE consists of Mn- and Co-rich phases, the structures of which are determined to be the L21B-type and disordered L21-type, respectively, according to anomalous XRD analysis. None of them forms the XA-type structure expected for SGS Heusler alloy, although they all show SGS characteristics. We suggest, to validate SGS characteristics, it is necessary to extract not only magnetic and electric transport properties but also information about microstructures and atomic-scale structures of the films including defects such as atomic swap.

Published
2020

9. Spontaneous Distortion and Ferromagnetism Induced by Quantum-well States in Pd(100) Ultrathin Films

Author

Sakuragi, Shunsuke, Tajiri, Hiroo, Kageshima, Hiroyuki, and Sato, Tetsuya

Subjects
Condensed Matter - Materials Science
Abstract

We study the crystal structure of Pd(100) ultrathin films, which show ferromagnetism induced by the quantum confinement effect, using in-situ X-ray crystal truncation rod measurement and density functional calculation. The energy gain due to the appearance of ferromagnetism in Pd results in flatter and uniform film growth of ferromagnetic Pd films compared with paramagnetic Pd. In addition, ferromagnetic Pd films expand the lattice constant in order to suppress the increase in kinetic energy of electrons accompanied by the occurrence of exchange splitting. Although the traditional theory of magnetism in metals indicates that the increase in density of states that induces ferromagnetism (Stoner criterion), our present finding reveals a mechanism of modulation in the density of states via the appearance of ferromagnetism, i.e., the inverse mechanism of Stoner's theory., Comment: 5 pages, 4 figures

Published
2016
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10. Nanosecond Phase Transition Dynamics in Compressively Strained Epitaxial BiFeO3

Author

Cosgriff, Margaret P., Chen, Pice, Lee, Sung Su, Lee, Hyeon Jun, Kuna, Lukasz, Pitike, Krishna C., Louis, Lydie, Parker, William D., Tajiri, Hiroo, Nakhmanson, Serge M., Jo, Ji Young, Chen, Zuhuang, Chen, Lang, and Evans, Paul G.

Subjects
Condensed Matter - Materials Science
Abstract

A highly strained BiFeO3 (BFO) thin film is transformed between phases with distinct structures and properties by nanosecond-duration applied electric field pulses. Time-resolved synchrotron x-ray microdiffraction shows that the steady-state transformation between phases is accompanied by a dynamical component that is reversed upon the removal of the field. Steady-state measurements reveal that approximately 20% of the volume of a BFO thin film grown on a LaAlO3 substrate can be reproducibly transformed between rhombohedral-like and tetragonal-like phases by electric field pulses with magnitudes up to 2 MV/cm. A transient component, in which the transformation is reversed following the end of the electric field pulse, can transform a similar fraction of the BFO layer and occurs rapidly time scale limited by the charging time constant of the thin film capacitor. The piezoelectric expansion of the tetragonal-like phase leads to a strain of up to 0.1%, with a lower limit of 10 pm/V for the piezoelectric coefficient of this phase. Density functional theory calculations provide insight into the mechanism of the phase transformation showing that imparting a transient strain of this magnitude favors a transformation from rhombohedral-like to tetragonal-like phase.

Published
2015

12. Atomic and Electronic Structures on a Mordenite Zeolite

Author

Hosokawa, Shinya, primary, Sato, Hitoshi, additional, Tezuka, Yasuhisa, additional, Adachi, Jun-ichi, additional, Kimura, Koji, additional, Hayashi, Koichi, additional, Kohara, Shinji, additional, Tajiri, Hiroo, additional, Kobayashi, Kentaro, additional, Koura, Akihide, additional, and Shimojo, Fuyuki, additional

Published
2023
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13. Origin of negative anisotropic magnetoresistance effect in Fe0.75Co0.25 single-crystal thin films upon Ir addition

Author

Toyama, Ryo, primary, Kokado, Satoshi, additional, Masuda, Keisuke, additional, Li, Zehao, additional, Kushwaha, Varun K., additional, Sasaki, Taisuke T., additional, Kumara, Loku Singgappulige Rosantha, additional, Koganezawa, Tomoyuki, additional, Tajiri, Hiroo, additional, Yamazaki, Takahiro, additional, Kotsugi, Masato, additional, Iwasaki, Yuma, additional, and Sakuraba, Yuya, additional

Published
2023
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18. Enhancing Atomic Ordering, Magnetic and Transport Properties of Mn2vgaheusler Alloy Thin Films Toward Negatively Spin-Polarized Charge Injection

Author

Li, Zehao, primary, Suto, Hirofumi, additional, Barwal, Vineet, additional, Masuda, Keisuke, additional, Sasaki, Taisuke, additional, Chen, Zixi, additional, Tajiri, Hiroo, additional, Kumara, Loku Singgappulige Rosantha, additional, Koganezawa, Tomoyuki, additional, Amemiya, Kenta, additional, Kokado, Satoshi, additional, Hono, Kazuhiro, additional, and Sakuraba, Yuya, additional

Published
2023
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26. Quantitative atomic order characterization of a Mn₂FeAl Heusler epitaxial thin film

Author

Kurdi, Samer, Sakuraba, Yuya, Masuda, Keisuke, Tajiri, Hiroo, Nair, Bhaskaran, Nataf, Guillaume F., Vickers, Mary E., Reiss, Günter, Meinert, Markus, Dhesi, Sarnjeet S., Ghidini, Massimo, and Barber, Zoe H.

Abstract

In this work, we investigate the effect of anti-site disorder on the half-metallic properties of a Mn₂FeAl Heusler alloy thin film. The film was grown on TiN-buffered MgO 001 substrates via magnetron sputtering. A detailed structural characterization using x-ray diffraction (XRD) and anomalous XRD showed that the film crystallizes in the partially disordered L2₁ B structure with 33% disorder between the Mn(B) and Al(D) sites. We measure a positive anisotropic magnetoresistance in the film, which is an indication of non-half metallic behaviour. Our x-ray magnetic circular dichroism sum rules analysis shows that Mn carries the magnetic moment in the film, with a positive Fe moment. Experimentally determined moments correspond most closely with those found by density functional calculated for the L2₁ B structure with Mn(B) and Al(D) site disorder, matching the experimental structural analysis. We thus attribute the deviation from half-metallic behaviour to the formation of the L2₁ B structure. To realize a half-metallic Mn₂FeAl film it is important that the inverse Heusler XA structure is stabilized with minimal anti-site atomic disorder.

Published
2022
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28. Structural Insight Using Anomalous XRD into Mn 2coal Heusler Alloy Films Grown by Magnetron Sputtering, IBAS, And MBE Techniques

Author

Tajiri, Hiroo, primary, Kumara, Loku Singgappulige Rosantha, additional, Sakuraba, Yuya, additional, Chen, Zixi, additional, Wang, Jian, additional, Zhou, Weinan, additional, Varun, Kushwaha, additional, Ueda, Kenji, additional, Yamada, Shinya, additional, Hayama, Kohei, additional, and Hono, Kazuhiro, additional

Published
2022
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29. Atomic and Electronic Structures of an Ag-Containing 4a Zeolite

Author

Hosokawa, Shinya, primary, Kobayashi, Kentaro, additional, Koura, Akihide, additional, Shimojo, Fuyuki, additional, Tezuka, Yasuhisa, additional, Adachi, Jun-ichi, additional, Onodera, Yohei, additional, Kohara, Shinji, additional, Tajiri, Hiroo, additional, Chokkalingam, Anand, additional, and Wakihara, Toru, additional

Published
2022
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30. Structural Dynamics of Adsorption Equilibrium for Iodine Adsorbed on Au(111)

Author

Nakamura, Masashi, Tanaka, Yuma, Takahashi, Masamitsu, Tajiri, Hiroo, Sakata, Osami, Hoshi, Nagahiro, and Masamitsu, Takahashi

Abstract

The structural dynamics of an iodide layer adsorbed on Au(111) were investigated using X-ray photon correlation spectroscopy (XPCS), electrochemical scanning tunneling microscopy (STM), and time-resolved Xray diffraction. At the adsorption equilibrium of iodide at a constant electrode potential, the STM images captured at regular intervals show the migration of atomic vacancy sites in the ordered adsorbed iodide layer. The results indicate that reversible adsorption/desorption and site conversion continuously occur at the equilibrium state. Although the transitions occur at various time scales according to the STM images, the time decay of the autocorrelation function at the specular position is estimated to be 127 s according to the XPCS measurement. The dynamics observed using XPCS suggest that the vertical relaxation of the surface layers is associated with the adsorption of iodide.

Published
2020

31. High L21-atomic ordering and spin-polarization in Co2MnZ (Z = Ge, Sn) Heusler thin films with low-temperature annealing process.

Author

Kushwaha, Varun Kumar, Sakuraba, Yuya, Nakatani, Tomoya, Sasaki, Taisuke, Kurniawan, Ivan, Miura, Yoshio, Tajiri, Hiroo, and Hono, Kazuhiro

Subjects
THIN films, ENHANCED magnetoresistance, TIN, ELECTRIC currents, TRANSITION temperature, HEUSLER alloys, FERROELECTRIC thin films
Abstract

Although an enhanced magnetoresistance (MR) has been observed in many Co2-based Heusler alloys by promoting their structural ordering from B2 to L21 by post-annealing at higher temperatures (Tann > 500 °C), it is desirable to search for other Heusler alloys that crystallize in L21-order below 300 °C, as the maximum Tann is restricted for processing devices. For Co2MnZ (Z = Ge, Sn) Heusler alloys, an L21-order is expected to appear even in the as-deposited state or by a low-temperature annealing process due to their very high L21 to B2-order transition temperature (>1500 K). Here, epitaxial Co2MnZ films were grown on MgO (001) substrate at room temperature (RT) and post-annealed at Tann = 200–500 °C. Interestingly, as-sputtered films exhibit L21-ordering, which improves systematically upon increasing Tann. The spin-polarization of electric current (β) was estimated at RT using nonlocal spin-valve (NLSV) devices by measuring the spin-accumulation signal in a copper (Cu) channel. It was found that at Tann = 300 °C, the β value of Co2MnGe films is higher (∼0.65) than that of Co2FeGe0.5Ga0.5 films due to a higher degree of L21-order, which makes the Co2MnGe alloy a promising ferromagnetic electrode for spintronic device applications. [ABSTRACT FROM AUTHOR]

Published
2022
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32. Structure of sustainable lead-free low-melting vanadate glass

Author

Onodera, Yohei, primary, Kohara, Shinji, additional, Aoyagi, Takuya, additional, Naito, Takashi, additional, Stellhorn, Jens R., additional, Hosokawa, Shinya, additional, Tajiri, Hiroo, additional, Hannon, Alex C., additional, Pusztai, László, additional, and Jóvári, Pál, additional

Published
2021
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33. Oxygen octahedral distortions in compressively strained SrRuO3 epitaxial thin films.

Author

Kan, Daisuke, Anada, Masato, Wakabayashi, Yusuke, Tajiri, Hiroo, and Shimakawa, Yuichi

Subjects
X-ray diffraction, SYNCHROTRONS, OCTAHEDRA, BRAGG'S law (Physics), ELECTRIC distortion
Abstract

We carried out the synchrotron X-ray diffraction measurements and investigated the oxygen octahedral distortions in compressively strained SrRuO3 epitaxial thin films on NdGaO3 substrates. We observed half-order Bragg reflections originating from the RuO6 octahedral distortions accommodated in the compressively strained films. Our structural analysis shows that the RuO6 octahedra are elongated along the out-of-plane direction and are rotated in the out-of-phase manner only about the out-of-plane direction. The RuO6 rotation angle γrot is 10.9° ± 1.2°, which is larger than that in the bulk SrRuO3. The results indicate that the substrate-induced compressive strain enhances the out-of-plane rotations while strongly suppressing the in-plane rotations. In fact, the half-order Bragg reflections arising from the octahedral rotations about the in-plane direction are found to be weak and broad, implying that the in-plane rotations exist only in the interface region, not in the entire film. This indicates that while the in-plane octahedral rotation propagates through the interfacial octahedral connections into the film, its propagation decays within the interface region because of the compressive strain. Our results indicate that both the substrate-induced strain and the interfacial octahedral connection play important roles in determining the octahedral distortions accommodated in the strained SrRuO3 films. [ABSTRACT FROM AUTHOR]

Published
2018
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34. Characterization of the ScAlMgO4 cleaving layer by X-ray crystal truncation rod scattering.

Author

Hanada, Takashi, Tajiri, Hiroo, Sakata, Osami, Fukuda, Tsuguo, and Matsuoka, Takashi

Subjects
*SCANDIUM compounds, *X-ray crystallography, *ION scattering, *SUPERLATTICE crystallography, *ALUMINUM compounds, *MANGANESE compounds, *OXIDES
Abstract

ScAlMgO4—easily cleaved in c-plane—forms a natural superlattice structure of a ScO2 layer and two Al0.5Mg0.5O layers stacking along c-axis. ScAlMgO4 is one of the RAMO4-type layered multicomponent oxides and a promising lattice-matching substrate material for InGaN and ZnO. Identification of the topmost layer and the surface atomic structure of the cleaved ScAlMgO4 (0001) are investigated by the X-ray crystal truncation rod scattering method. It is confirmed that ScAlMgO4 is cleaved between the two Al0.5Mg0.5O layers. The two parts separated at this interlayer are inversion symmetric to each other and without surface charge. This prevents parallel-plate-capacitor-like electrostatic force during the cleavage. Two different mechanisms are proposed for the two types of cleavage caused by the impact of a wedge and by the in-plane stress due to an overgrown thick GaN film. It is also revealed that about 10%–20% of the topmost O atoms are desorbed during a surface cleaning at 600 °C in ultra-high vacuum. Surface observations using reflection high-energy electron diffraction are possible only after the high-temperature cleaning because the electrical conduction caused by the oxygen deficiency prevents the charge-up of the insulating sample. [ABSTRACT FROM AUTHOR]

Published
2018
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44. Synchrotron X-ray Scattering Measurements of Disordered Materials

Author

Song, Chulho, Kohara, Shinji, Ohara, Koji, Tajiri, Hiroo, Sakata, Osami, Usuki, Takeshi, Benino, Yasuhiko, Mizuno, Akitoshi, Masuno, Atsunobu, Okada, Junpei T., Ishikawa, Takehiko, and Hosokawa, Shinya

Subjects
Materials science, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Molecular physics, law.invention, Optics, law, Physical and Theoretical Chemistry, Liquid, Amorphous Materials, business.industry, Scattering, Small-angle X-ray scattering, High-energy X-ray Scattering, 021001 nanoscience & nanotechnology, Small-angle neutron scattering, Synchrotron, 0104 chemical sciences, Anomalous X-ray Scattering, X-ray Raman scattering, 428.4, Grazing-incidence small-angle scattering, Glass, Biological small-angle scattering, Anomalous X-ray scattering, 0210 nano-technology, business
Abstract

著者人数: 12名, Accepted: 2015-10-08, 資料番号: SA1150319000

Published
2016

45. Impact of Local Atomic Fluctuations on Superconductivity of Pr-Substituted CaFe2As2 Studied by X-ray Fluorescence Holography

Author

Kudo, Kazutaka, primary, Ioka, Satoshi, additional, Happo, Naohisa, additional, Ota, Hiromi, additional, Ebisu, Yoshihiro, additional, Kimura, Koji, additional, Hada, Takuma, additional, Kimura, Takumi, additional, Tajiri, Hiroo, additional, Hosokawa, Shinya, additional, Hayashi, Kouichi, additional, and Nohara, Minoru, additional

Published
2019
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48. Facile preparation of hybrid thin films composed of spin-crossover nanoparticles and carbon nanotubes for electrical memory devices

Author

Tanaka, Daisuke, primary, Aketa, Naoki, additional, Tanaka, Hirofumi, additional, Horike, Satoshi, additional, Fukumori, Minoru, additional, Tamaki, Takashi, additional, Inose, Tomoko, additional, Akai, Tomoki, additional, Toyama, Hirotaka, additional, Sakata, Osami, additional, Tajiri, Hiroo, additional, and Ogawa, Takuji, additional

Published
2019
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