12 results on '"Morito Namba"'
Search Results
2. A Partial Anion Disorder in SrVO2H Induced by Biaxial Tensile Strain
- Author
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Morito Namba, Hiroshi Takatsu, Wataru Yoshimune, Aurélien Daniel, Shoichi Itoh, Takahito Terashima, and Hiroshi Kageyama
- Subjects
oxyhydrides ,SrVO2H ,thin film ,epitaxial strain ,cis/trans configuration ,order–disorder ,Inorganic chemistry ,QD146-197 - Abstract
SrVO2H, obtained by a topochemical reaction of SrVO3 perovskite using CaH2, is an anion-ordered phase with hydride anions exclusively at the apical site. In this study, we conducted a CaH2 reduction of SrVO3 thin films epitaxially grown on KTaO3 (KTO) substrates. When reacted at 530 °C for 12 h, we observed an intermediate phase characterized by a smaller tetragonality of c/a = 0.96 (vs. c/a = 0.93 for SrVO2H), while a longer reaction of 24 h resulted in the known phase of SrVO2H. This fact suggests that the intermediate phase is a metastable state stabilized by applying tensile strain from the KTO substrate (1.4%). In addition, secondary ion mass spectrometry (SIMS) revealed that the intermediate phase has a hydrogen content close to that of SrVO2H, suggesting a partially disordered anion arrangement. Such kinetic trapping of an intermediate state by biaxial epitaxial strain not only helps to acquire a new state of matter but also advances our understanding of topochemical reaction processes in extended solids.
- Published
- 2020
- Full Text
- View/download PDF
3. Dehydration of Electrochemically Protonated Oxide: SrCoO2 with Square Spin Tubes
- Author
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Maokun Wu, Yoji Kobayashi, Hiroshi Kageyama, Morito Namba, Qianmei Lin, Cédric Tassel, Wei-Hua Wang, Haobo Li, Chengchao Zhong, Takahito Terashima, Yu Cao, Shunsuke Kobayashi, Hiroshi Takatsu, Masaki Kobayashi, Yoshinori Kotani, Daichi Kato, Akihide Kuwabara, and Koji Fujita
- Subjects
Chemistry ,Inorganic chemistry ,Oxide ,chemistry.chemical_element ,Protonation ,General Chemistry ,Electrochemistry ,Biochemistry ,Oxygen ,Catalysis ,Metal ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Transition metal ,visual_art ,Yield (chemistry) ,visual_art.visual_art_medium ,Thin film - Abstract
Controlling oxygen deficiencies is essential for the development of novel chemical and physical properties such as high-Tc superconductivity and low-dimensional magnetic phenomena. Among reduction methods, topochemical reactions using metal hydrides (e.g., CaH2) are known as the most powerful method to obtain highly reduced oxides including Nd0.8Sr0.2NiO2 superconductor, though there are some limitations such as competition with oxyhydrides. Here we demonstrate that electrochemical protonation combined with thermal dehydration can yield highly reduced oxides: SrCoO2.5 thin films are converted to SrCoO2 by dehydration of HSrCoO2.5 at 350 °C. SrCoO2 forms square (or four-legged) spin tubes composed of tetrahedra, in contrast to the conventional infinite-layer structure. Detailed analyses suggest the importance of the destabilization of the SrCoO2.5 precursor by electrochemical protonation that can greatly alter reaction energy landscape and its gradual dehydration (H1-xSrCoO2.5-x/2) for the SrCoO2 formation. Given the applicability of electrochemical protonation to a variety of transition metal oxides, this simple process widens possibilities to explore novel functional oxides.
- Published
- 2021
4. Chemical Pressure Effect on Structural and Physical Properties of 15R-SrVO2.2N0.6 with Anion-Vacancy Order
- Author
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Kantaro Murayama, Hiroshi Takatsu, Masayuki Ochi, Morito Namba, Kazuhiko Kuroki, and Hiroshi Kageyama
- Subjects
General Physics and Astronomy - Published
- 2022
5. Epitaxial Stabilization of SrCu3O4 with Infinite Cu3/2O2 Layers
- Author
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Hiroshi Takatsu, Naoya Yamashina, Morito Namba, Kazuhiko Kuroki, Takahito Terashima, Masayuki Ochi, and Hiroshi Kageyama
- Subjects
Superconductivity ,Condensed Matter - Materials Science ,Valence (chemistry) ,Condensed matter physics ,010405 organic chemistry ,Chemistry ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,010402 general chemistry ,Epitaxy ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Octahedron ,X-ray photoelectron spectroscopy ,Electrical resistivity and conductivity ,Metastability ,Physical and Theoretical Chemistry ,Molecular beam epitaxy - Abstract
We report the epitaxial thin film synthesis of SrCu$_3$O$_4$ with infinitely stacked Cu$_3$O$_4$ layers composed of edge-sharing CuO$_4$ square-planes, using molecular beam epitaxy. Experimental and theoretical characterizations showed that this material is a metastable phase that can exist by applying tensile biaxial strain from the (001)-SrTiO$_3$ substrate. SrCu$_3$O$_4$ shows an insulating electrical resistivity in accordance with the Cu$^{2+}$ valence state revealed X-ray photoelectron spectroscopy. First-principles calculations also indicated that the unoccupied $d_{3z^2-r^2}$ band becomes substantially stabilized owing to the absence of apical anions, in contrast to $A_2$Cu$_3$O$_4$Cl$_2$ ($A = $Sr, Ba) with an $A_2$Cl$_2$ block layer and therefore a trans-CuO$_4$Cl$_2$ octahedron. These results suggest that SrCu$_3$O$_4$ is a suitable parent material for electron-doped superconductivity based on the Cu$_3$O$_4$ plane., 1 column, 22 pages, 6 figures, Supporting Information
- Published
- 2020
6. Dehydration of Electrochemically Protonated Oxide: SrCoO
- Author
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Hao-Bo, Li, Shunsuke, Kobayashi, Chengchao, Zhong, Morito, Namba, Yu, Cao, Daichi, Kato, Yoshinori, Kotani, Qianmei, Lin, Maokun, Wu, Wei-Hua, Wang, Masaki, Kobayashi, Koji, Fujita, Cédric, Tassel, Takahito, Terashima, Akihide, Kuwabara, Yoji, Kobayashi, Hiroshi, Takatsu, and Hiroshi, Kageyama
- Abstract
Controlling oxygen deficiencies is essential for the development of novel chemical and physical properties such as high
- Published
- 2021
7. Single-crystal thin film growth of the Mott insulator EuVO3 under biaxial substrate strain
- Author
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Hiroshi Takatsu, Morito Namba, Takahito Terashima, and Hiroshi Kageyama
- Subjects
Inorganic Chemistry ,Materials Chemistry ,Condensed Matter Physics - Published
- 2022
8. Strain-assisted topochemical synthesis of la-doped SrVO2H Films
- Author
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Hiroshi Takatsu, Takahito Terashima, Masayuki Ochi, Morito Namba, Hiroshi Kageyama, Kazuhiko Kuroki, Aurelien Daniel, Haobo Li, Kyoto University, Osaka University [Osaka], Ecole Superieure d'Ingenieurs de Rennes [Rennes] (ESIR), Université de Rennes (UR), Center for Information Technology, CITJapan Society for the Promotion of Science, KAKEN: 16H06438, 17H04849, 17H05481, 18K13470, 19H04697, 20H00384, 20K21208, 21K05227, JP19H05058, JPJSCCA20200004Core Research for Evolutional Science and Technology, CREST: JPMJCR142, JPMJCR20R2University of Tokyo: hp200007Research Foundation for the Electrotechnology of Chubu, REFEC, Kyoto University [Kyoto], Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), and Université de Rennes (UNIV-RENNES)
- Subjects
Secondary ion mass spectrometry ,Materials science ,Thin films ,Aliovalent substitution ,Mixed-anion compounds ,Theoretical calculations ,02 engineering and technology ,Perovskite ,01 natural sciences ,Lanthanum compounds ,Negative ions ,SrTiO3 substrates ,0103 physical sciences ,Substrate strain ,Semiconductor doping ,[CHIM]Chemical Sciences ,General Materials Science ,Topochemical reaction ,010306 general physics ,Mott insulators ,Strain (chemistry) ,Doping ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Secondary ion mass spectroscopy ,Vanadium compounds ,Crystallography ,Strontium titanates ,0210 nano-technology ,Calculations ,Two-dimensional correlation - Abstract
International audience; Perovskite oxyhydride SrVO2H (V3+, d2) is a Mott insulator with a strong two-dimensional correlation due to anion ordering. In this study, we attempted electron doping by aliovalent substitution. Although Sr1-xLaxVO3 thin films (x ≤ 0.4) on a SrTiO3 substrate were topochemically reduced using CaH2, vanadium of the reduced films retained the trivalent state. Combined with the results of secondary ion mass spectroscopy, we conclude that Sr1-xLaxVO2+xH1-x is obtained, where the apical oxygen site is partially replaced by hydride anions. First-principles theoretical calculations highlight the role played by compressive biaxial strain in stabilizing the charge-compensated Sr1-xLaxVO2+xH1-x phase, rather than the electron-doped Sr1-xLaxVO2H. The present study demonstrates that topochemical reactions combined with substrate strain provide various opportunities to widen the compositional space in mixed-anion compounds. ©
- Published
- 2021
9. A Partial Anion Disorder in SrVO2H Induced by Biaxial Tensile Strain
- Author
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Wataru Yoshimune, Hiroshi Takatsu, Aurelien Daniel, Hiroshi Kageyama, Shoichi Itoh, Morito Namba, and Takahito Terashima
- Subjects
order–disorder ,Materials science ,oxyhydrides ,Hydride ,thin film ,Substrate (chemistry) ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,lcsh:QD146-197 ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,Secondary ion mass spectrometry ,Crystallography ,epitaxial strain ,Phase (matter) ,Metastability ,lcsh:Inorganic chemistry ,Intermediate state ,SrVO2H ,0210 nano-technology ,cis/trans configuration ,Perovskite (structure) - Abstract
SrVO2H, obtained by a topochemical reaction of SrVO3 perovskite using CaH2, is an anion-ordered phase with hydride anions exclusively at the apical site. In this study, we conducted a CaH2 reduction of SrVO3 thin films epitaxially grown on KTaO3 (KTO) substrates. When reacted at 530 °, C for 12 h, we observed an intermediate phase characterized by a smaller tetragonality of c/a = 0.96 (vs. c/a = 0.93 for SrVO2H), while a longer reaction of 24 h resulted in the known phase of SrVO2H. This fact suggests that the intermediate phase is a metastable state stabilized by applying tensile strain from the KTO substrate (1.4%). In addition, secondary ion mass spectrometry (SIMS) revealed that the intermediate phase has a hydrogen content close to that of SrVO2H, suggesting a partially disordered anion arrangement. Such kinetic trapping of an intermediate state by biaxial epitaxial strain not only helps to acquire a new state of matter but also advances our understanding of topochemical reaction processes in extended solids.
- Published
- 2020
- Full Text
- View/download PDF
10. Dehydration of electrochemically protonated oxide: SrCoO2with square spin tubes.
- Author
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Hao-Bo Li, Shunsuke Kobayashi, Chengchao Zhong, Morito Namba, Yu Cao, Daichi Kato, Yoshinori Kotani, Qianmei Lin, Maokun Wu, Wei-Hua Wang, Masaki Kobayashi, Koji Fujita, Cédric Tassel, Takahito Terashima, Akihide Kuwabara, Yoji Kobayashi, Hiroshi Takatsu, and Hiroshi Kageyama
- Published
- 2021
- Full Text
- View/download PDF
11. Spin Frustration in Protonated Rutile Oxides.
- Author
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Kazuki Takaoka, Morito Namba, Haobo Li, Kodai Ishida, Hiroshi Takatsu, and Hiroshi Kageyama
- Abstract
We report the topochemical protonation of rutile oxides Rh
0.5 V0.5 O2 and Cr0.5 V0.5 O2 by low-temperature hydrogen gas treatment. After the treatment, nonmagnetic V5+ (d0 ) ions were selectively reduced to +3.5 (d1.5 ) for Hx Rh0.5 V0.5 O2 (x ~ 0.75) and +4 (d¹) for Hx Cr0.5 V0.5 O2 (x ~0.5 ). Hx Rh0.5 V0.5 O2 with nonmagnetic Rh3+ ions has weak magnetic interactions with a spin glass transition at Tf = 6 K. In contrast, protonation of Cr0.5 V0.5 O2 with Cr3+ (d³) enhances antiferromagnetic interactions with the Weiss temperature of θ = -199(1) K. However, the spin glass transition temperature is still low (Tf = 10 K), indicating competing interactions, in which a frustration factor of 20 is the largest among rutile compounds. Topochemical protonation can be a useful method for extending the family of magnetic oxides. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
12. Strain-induced creation and switching of anion vacancy layers in perovskite oxynitrides
- Author
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Masatomo Yashima, Takao Mori, Shunsaku Kitagawa, Wenhao Sun, Takahiro Maruyama, Kotaro Fujii, Takashi Honda, Toshiya Otomo, Akira Chikamatsu, Shunsuke Yamashita, Kazutaka Ikeda, Koji Kimoto, Masayuki Ochi, Masahito Sano, Kenji Ishida, Tetsuya Hasegawa, Daiichiro Sekiba, Yasushi Hirose, Fumitaka Takeiri, Hiroshi Takatsu, Kazuhiko Kuroki, Nana Izumo, Craig M. Brown, Morito Namba, Yuki Sugisawa, Hiroshi Kageyama, Takahide Nakashima, and Takafumi Yamamoto
- Subjects
Materials science ,Electronic materials ,Science ,Superlattice ,Oxide ,General Physics and Astronomy ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,Epitaxy ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,chemistry.chemical_compound ,Vacancy defect ,Thin film ,Perovskite (structure) ,Multidisciplinary ,Heterojunction ,Solid-state chemistry ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Chemical physics ,0210 nano-technology - Abstract
Perovskite oxides can host various anion-vacancy orders, which greatly change their properties, but the order pattern is still difficult to manipulate. Separately, lattice strain between thin film oxides and a substrate induces improved functions and novel states of matter, while little attention has been paid to changes in chemical composition. Here we combine these two aspects to achieve strain-induced creation and switching of anion-vacancy patterns in perovskite films. Epitaxial SrVO3 films are topochemically converted to anion-deficient oxynitrides by ammonia treatment, where the direction or periodicity of defect planes is altered depending on the substrate employed, unlike the known change in crystal orientation. First-principles calculations verified its biaxial strain effect. Like oxide heterostructures, the oxynitride has a superlattice of insulating and metallic blocks. Given the abundance of perovskite families, this study provides new opportunities to design superlattices by chemically modifying simple perovskite oxides with tunable anion-vacancy patterns through epitaxial lattice strain., Using strain to control oxynitride properties. 京都大学プレスリリース. 2020-12-01., 原子空孔の配列を制御する新手法の発見. 京都大学プレスリリース. 2020-12-02.
- Published
- 2020
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