Updated on 2025/04/09

写真a

 
IKEDA Naoshi
 
Organization
Faculty of Environmental, Life, Natural Science and Technology Professor
Position
Professor
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Degree

  • 博士(理学) ( 早稲田大学 )

Research Interests

  • 誘電体

  • ferroelectrics

  • 磁性体

  • electronic ferroelectricity

  • フラストレーション

Research Areas

  • Natural Science / Magnetism, superconductivity and strongly correlated systems

  • Natural Science / Semiconductors, optical properties of condensed matter and atomic physics

  • Natural Science / Mathematical physics and fundamental theory of condensed matter physics  / 電子強誘電体

Research History

  • - Professor,Mathematics and Physics,Graduate School of Natural Science and Technology,Okayama University

    2006

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  • - 岡山大学自然科学研究科数理物理科学専攻 教授

    2006

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Papers

  • Ginzburg-Landau action and polarization current in an excitonic insulator model of electronic ferroelectricity

    Hiroto Adachi, Naoshi Ikeda, Eiji Saitoh

    Physical Review B   107 ( 15 )   2023.4

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.107.155142

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.107.155142/fulltext

  • Formation of Binderless Carbon Short Fibers Structure by Fiber Aerosol Deposition Reviewed

    M. Mori, S. Mori, M. Nishikawa, N. Ikeda

    Journal of the Japanese Society for Experimental Mechanics   22 ( 4 )   255 - 259   2023.1

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    Authorship:Last author   Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.11395/jjsem.22.255

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  • Direct evidence of electronic ferroelectricity in YbFe<inf>2</inf>O<inf>4</inf> using neutron diffraction and nonlinear spectroscopy

    K. Fujiwara, Y. Fukada, Y. Okuda, R. Seimiya, N. Ikeda, K. Yokoyama, H. Yu, S. Koshihara, Y. Okimoto

    Scientific Reports   11 ( 1 )   2021.12

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    Publishing type:Research paper (scientific journal)  

    We report the first observation of room temperature spontaneous electric polarization in an electronic ferroelectric material, a YbFe2O4 single crystal. The observation was based on second harmonic generation (SHG), a nonlinear optical process. Tensor analysis of the SHG signal revealed that this material has a polar charge superstructure with Cm symmetry. This result settles the long-term discussion on the uncertainty about electronic ferroelectric properties, including the charge order structure. We present a complete picture of the polar charge ordering of this material via consistent results from two different characterization methods. The SHG signal shows the same temperature dependence as the superlattice signal observed in neutron diffraction experiments. These results prove ferroelectric coupling to electron ordering in YbFe2O4, which results in electronic ferroelectricity which is enabled by the real space ordering of iron cations with different valences. The existence of electronic ferroelectricity holds promise for future electronics technologies where devices run a thousand times faster than frequency of the present CPU (a few gigahertz) embedded in smartphones, etc.

    DOI: 10.1038/s41598-021-83655-6

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  • Present status of the experimental aspect of RFe2O4 study

    Naoshi Ikeda, Tomoko Nagata, Jun Kano, Shigeo Mori

    JOURNAL OF PHYSICS-CONDENSED MATTER   27 ( 5 )   2015.2

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    Language:English   Publisher:IOP PUBLISHING LTD  

    We give a brief review of the experimental research on a triangular mixed valence iron oxide RFe2O4 (R = Y, Dy, Ho, Er, Tm, Yb, Lu, Sc or In). Interest in this material has been increasing every year because of the fascinating but complicated interaction between spin, charge and the orbital state of iron ions in frustrated geometry. Reports collected in this review cover experimental research on crystallography, chemical analysis, bulk and thin film preparation, magnetic, dielectric, diffraction with neutrons, x-ray and electron, optical and x-ray absorption, Mossbauer spectroscopy and other methods that incorporate the use of modern scientific technology and knowledge. The report mainly focuses on experimental facts since 1990 on which an early review by Siratori has been published (Kimizuka et al 1990 Handbook on the Physics and Chemistry of Rare Earths vol 13, ed K A Gschneidner Jr and L Eyring

    DOI: 10.1088/0953-8984/27/5/053201

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  • Superconductivity in alkali-metal-doped picene

    Ryoji Mitsuhashi, Yuta Suzuki, Yusuke Yamanari, Hiroki Mitamura, Takashi Kambe, Naoshi Ikeda, Hideki Okamoto, Akihiko Fujiwara, Minoru Yamaji, Naoko Kawasaki, Yutaka Maniwa, Yoshihiro Kubozono

    NATURE   464 ( 7285 )   76 - 79   2010.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE PUBLISHING GROUP  

    Efforts to identify and develop new superconducting materials continue apace, motivated by both fundamental science and the prospects for application. For example, several new superconducting material systems have been developed in the recent past, including calcium-intercalated graphite compounds(1), boron-doped diamond(2) and-most prominently-iron arsenides such as LaO(1-x)F(x)FeAs (ref. 3). In the case of organic superconductors, however, no new material system with a high superconducting transition temperature (T(c)) has been discovered in the past decade. Here we report that intercalating an alkali metal into picene, a wide-bandgap semiconducting solid hydrocarbon, produces metallic behaviour and superconductivity. Solid potassium-intercalated picene (K(x)picene) shows T(c) values of 7K and 18 K, depending on the metal content. The drop of magnetization in Kxpicene solids at the transition temperature is sharp (&lt;2 K), similar to the behaviour of Ca-intercalated graphite(1). The Tc of 18K is comparable to that of K-intercalated C(60) (ref. 4). This discovery of superconductivity in K(x)picene shows that organic hydrocarbons are promising candidates for improved T(c) values.

    DOI: 10.1038/nature08859

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Books

  • 鉄複電荷酸化物 RFe2O4 が示す電子強誘電性の研究

    沖本洋一, 藤井達生, 池田 直( Role: Joint author ,  執筆責任者)

    日本結晶学会  2024.5 

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  • 電子秩序化型誘電体の共鳴散乱

    シーエムシー出版  2008 

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  • 機能物質・材料開発と放射光-SPring-8の産業利用

    シーエムシー出版(東京)  2008 

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  • 三角格子系鉄複合酸化物LuFe2O4における電荷秩序構造と誘電特性

    日本結晶学会  2008 

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  • NaV2O5 の逐次電荷不均化による悪魔の花相図

    日本放射光学会  2008 

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MISC

  • 金属-酸化物薄膜接合系におけるエネルギーバンドアライメント

    狩野旬, 押目典宏, 廣瀬哲, 上田剛慈, 安井伸太郎, 浜嵜容丞, 伊藤満, 三上仁志, 池田直, 藤井達生, 柏原浩大, SCHNEIDER Julien

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   80th   2019

  • 化学等量性のよいLuFe2O4の酸素欠損と磁性

    奥田洋平, 藤原孝将, 清宮僚人, 横山景祐, 沖本洋一, 腰原伸也, 安井伸太郎, 加倉井和久, 加倉井和久, 池田直

    日本物理学会講演概要集(CD-ROM)   74 ( 1 )   2019

  • Core-level binding-energy of BaTiO3 with pre- and post-application of electric field

    Oshime N., Itoh M., Fujii T., Yasui A., Kano J., Ikenaga E., Yasui S., Hinokuma S., Ikeda N., Hamasaki Y., Yasuhara S., Yokoya T.

    Meeting Abstracts of the Physical Society of Japan   73   2571 - 2571   2018

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    Language:Japanese   Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.73.1.0_2571

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  • 分極効果で変調される強誘電体BaTiO3薄膜の電子構造

    押目典宏, 狩野旬, 狩野旬, 池永英司, 安井伸太郎, 日隈聡士, 池田直, 浜嵜容丞, 安原颯, 横谷尚睦, 伊藤満, 藤井達生, 保井晃

    日本セラミックス協会年会講演予稿集(CD-ROM)   2018   2018

  • 分極効果で変調される強誘電体BaTiO3薄膜の電子構造

    押目典宏, 狩野旬, 狩野旬, 池永英司, 安井伸太郎, 日隈聡士, 池田直, 浜嵜容丞, 安原颯, 横谷尚睦, 伊藤満, 藤井達生, 保井晃

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   65th   2018

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Presentations

  • Correlation among magnetic field, spin fluctutaion, and electric polarization exhibited by electronic ferroelectric oxide RFe2O4 in nonmangetic state Invited

    Naoshi Ikeda

    REIMEI Workshop: Physics of Advanced Functional Materials  2024.10.11 

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    Event date: 2024.10.10 - 2024.10.11

    Language:English   Presentation type:Oral presentation (invited, special)  

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  • Electronic Ferroelectricity in RFe2O4 Invited

    Naoshi Ikeda, Yoichi Okimoto

    The 14th Japan-Korea Conference on Ferroelectricity  2024.9.1 

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    Event date: 2024.8.29 - 2024.9.1

    Language:English   Presentation type:Oral presentation (keynote)  

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  • RFe2O4の電子強誘電性の起源 Invited

    池田直

    産業技術総合研究所 電子光基礎技術研究部門 講演会  2024.6.20 

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    Event date: 2024.6.20

    Presentation type:Oral presentation (invited, special)  

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  • Pd触媒のNO‐CO反応における担体効果

    重名智博, 狩野旬, 藤井達生, 森茂生, 池田直

    日本物理学会講演概要集(CD-ROM)  2018.3.23 

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    Event date: 2018.3.23

    Language:Japanese  

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  • Unusual valence change of metal nanoparticles on the ferroelectric II

    Yoshida T, Fujii T, Ohkubo T, Ueda T, Kano J, Mizumaki M, Nitta K, Kato K, Hinokuma H, Oshime N, Ikeda N

    Meeting Abstracts of the Physical Society of Japan  2017  The Physical Society of Japan

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    Event date: 2017

    Language:Japanese  

    &lt;p&gt;強誘電体に金属ナノ粒子を接合させると強誘電体の分極により金属の電子状態が変調すると考えられる。電子状態変化が触媒作用に影響することが示唆されているが、電子状態異常の直接的な観測例はない。今回、強誘電体BaTiO_3_表面に担持したPdO_x_ナノ粒子に対してX線吸収微細構造(XAFS)測定を行い、粒子表面で異常な価数状態をとることを見出した、またその発現機構についての考察を行ったので報告する。&lt;/p&gt;

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Works

  • 酸化鉄加工物「グリーンフェライト(R)」を用いた次世代型太陽電池の実用化に向けた取組

    2013

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Awards

  • 日本物理学会第70回年次大会 領域10 学生奨励賞

    2015  

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    Country:Japan

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  • 日本物理学会2015年秋季大会 領域10 学生奨励賞

    2015  

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    Country:Japan

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  • ポスター賞(第6回誘電体若手夏の学校)

    2014  

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    Country:Japan

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  • Future Ferroelectrics 2014 Presentation Award

    2014  

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  • ポスター賞(ISIAME2012 Poster Award)

    2012  

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    Country:Japan

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Research Projects

  • 希土類複合酸化物における電子強誘電性の電界・光・磁場による分極制御とイメージング

    Grant number:22H01153  2022.04 - 2025.03

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    沖本 洋一, 池田 直

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    Grant amount:\17680000 ( Direct expense: \13600000 、 Indirect expense:\4080000 )

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  • Successive charge order pahse transition in electronic ferroelectrics

    Grant number:22H01942  2022.04 - 2025.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    池田 直, 藤井 達生, 沖本 洋一, 藤原 孝将

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    Grant amount:\17420000 ( Direct expense: \13400000 、 Indirect expense:\4020000 )

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  • Development of new magnetic memory devices using nagative magnetizaion oxides

    Grant number:20H02829  2020.04 - 2023.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    吉井 賢資, 池田 直, 矢板 毅

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    Grant amount:\17420000 ( Direct expense: \13400000 、 Indirect expense:\4020000 )

    前年度の結果を踏まえ、主に、室温近傍で負の磁性が見られたスピネル系の探索を行った。放射光吸収データを用いた局所構造は確定していないため、他のアプローチで研究を行った。応用的見地から、ニッケルよりもクラーク数の大きいマンガンに一部置換するなどの合成を試みたが、現状では負の磁性は観測されていない。さらには、リチウム鉄スピネルなどアルカリ金属を含む系についても探索を行った。負の磁性は見られたものの、負の磁性が発現する温度(補償温度)は最高で280K近傍であり、室温には到達していない。
    別のアプローチとして、過去の論文から、ペロブスカイトクロム酸化物を還元雰囲気中で加熱すると磁気転移温度が上昇するという報告があるため、この手法を試行した。負の磁性を示す(La,Pr)CrO3およびGdCrO3について、CO-CO2混合ガス雰囲気中で1000℃近傍での加熱を行った。COとCO2の流量比は3:1程度で試行した。(La,Pr)CrO3およびGdCrO3の磁気転移温度はそれぞれ250Kおよび170K近傍であり、還元雰囲気での加熱においては1Kほどの上昇傾向が見られたものの、大幅な上昇は観測されなかった。
    以上と並行し、派生的な研究を報告した。磁気冷凍物質の可能性が指摘されている上記GdCrO3について、5%程度Biを置換して合成すると、固相反応における合成温度が1100℃から900℃近辺まで下がることを学会にて報告した。また、クロム酸化物の新規物性の探索を行い、190KにおいてCrとCuの電荷秩序転移と磁気転移が同時に起こるBiCu3Cr4O12において、2つの秩序を同時に用いて効率的な冷凍が行えるマルチ熱量効果を論文発表した。また、電子誘電体RFe2O4について、イオン半径の異なる2つの系の電子線回折測定を行い、鉄三角格子間の距離によって電荷秩序構造の次元性が変化することを論文で報告した。

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  • Precise study on the optical and dielectric response of the stoichiometric iron based electronic ferroelectrics

    Grant number:19H01827  2019.04 - 2022.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    IKEDA NAOSHI

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    Grant amount:\17420000 ( Direct expense: \13400000 、 Indirect expense:\4020000 )

    This research has demonstrated for the first time in the world that an electron ferroelectric material exists stably at room temperature. Furthermore, we were able to show that this electronic phase also exists in thin film samples. The electric polarization consisting of only the electron distribution in the electron ferroelectric material is expected to respond significantly faster than that in the displacement-type ferroelectric material, which has been known until now.
    A new dielectric relaxation analysis method using single crystals was developed for the electric polarization of electronic ferroelectrics, which inevitably involves the electric resistivity. As a result, we were able to experimentally show for the first time that in fine charge-ordered domains, charge-ordered nanoregions with larger capacitance have higher electrical resistance.

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  • Fabrication of room-temperature multiferroic materials by rare-earth iron oxide system with triangular lattices

    Grant number:18H02057  2018.04 - 2022.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    FUJII Tatsuo

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    Grant amount:\17550000 ( Direct expense: \13500000 、 Indirect expense:\4050000 )

    RFe2O4 is expected as a next-generation multiferroic material. We attempted to synthesize its single-crystalline film by the sputtering method. As a result, the in-plane orientation of the RFe2O4 layer on the sapphire substrate rotates 30 ° depending on the presence of the Fe3O4 buffer layer. When Fe3O4 and RFe2O4 are laminated to form a multilayer film, the in-plane orientation also depends on their stacking order. In addition, when using the YSZ single crystal substrate, we succeeded in obtaining an RFe2O4 thin film that does not have twin domains and is almost completely composed of single domains.

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Class subject in charge

  • Application of Condensed Matter Physics using Synchrotron Radiation (2024academic year) Concentration  - その他

  • Structural Physics using Synchrotron Radiation (2024academic year) Concentration  - その他

  • Solid-State Synchrotron Spectroscopy (2024academic year) Prophase  - 火1~2

  • Condensed Matter Physics using Synchrotron Radiation (2024academic year) Concentration  - その他

  • Synchrotron Material Science Course (2024academic year) Concentration  - その他

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