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小嶋 隆幸  コジマ タカユキ

教員組織学術研究院(繊維学系)電話番号
教育組織繊維学部 化学・材料学科FAX番号
職名助教(テニュア・トラック)メールアドレス
住所〒386-8567 長野県上田市常田3-15-1ホームページURLhttps://takayukikojimaresearch.web.fc2.com

プロフィール

研究分野
構造材料、機能材料
キーワード:機能性材料 , 薄膜 , 触媒 , 磁性材料
所属学会
所属学会
触媒学会
日本磁気学会
日本金属学会
日本表面科学会
学歴
出身大学院
2013 , 東北大学大学院 , 工学研究科 , 知能デバイス材料学専攻

出身学校・専攻等(大学院を除く)
2008 , 東北大学 , 工学部 , 材料科学総合学科
2006 , 久留米工業高等専門学校 , 材料工学科

取得学位
博士(工学) , 東北大学
受賞学術賞
2023 , JIM Young Leaders International Scholar Award
2019 , 第25回 青葉工学研究奨励賞
2019 , 第59回 原田研究奨励賞
2019 , 第29回 トーキン科学技術賞 最優秀賞・トーキン財団特別賞 重賞
2017 , 第27回 日本金属学会若手講演論文賞
2017 , 第27回 日本金属学会奨励賞
2013 , 第27回 独創性を拓く 先端技術大賞 「特別賞」
2013 , 第32回 表面科学学術講演会 講演奨励賞 (スチューデント部門)
2012 , 平成24年度日本磁気学会論文賞
2006 , 日本金属学会・日本鉄鋼協会 九州支部長賞
研究職歴等
研究職歴
2020- , 信州大学, 繊維学部 化学・材料学科, 助教 (卓越研究員)
2019-2019 , Technische Universität Chemnitz, Visiting Researcher
2015-2020 , 東北大学, 学際科学フロンティア研究所, 助教
2014-2014 , 東北大学, 多元物質科学研究所, 博士研究員
2013-2014 , 東北大学, 金属材料研究所, 博士研究員
2011-2013 , 日本学術振興会, 特別研究員(DC2)

研究活動業績

研究業績(著書・
発表論文等)
書籍等出版物
第2編 第2章 [4] 256th ACS National Meeting & Exposition, 触媒年鑑「触媒技術の動向と展望 2019」
触媒学会 2019(Apr.)
Author:小嶋 隆幸


第2編 第4章 第4節, L10型FeNi超格子薄膜材料の作製と磁気特性, 次世代永久磁石の開発最前線 ~磁性の解明から構造解析、省・脱レアアース磁石、モータ応用まで~
エヌ・ティー・エス 2019(Feb.)
Author:水口将輝; 小嶋隆幸; 高梨弘毅


論文
Co2FeGe Heusler Alloy Nanoparticle Catalysts for Propyne Hydrogenation and Ammonia Decomposition
ChemistryOpen,12(11) 2023(Nov. 06)
Author:Takayuki Kojima; Yuki Nakaya; Souta Tate; Satoshi Kameoka; Shinya Furukawa
Abstract:Abstract Heusler alloys (X2YZ) can be a candidate for new catalysts as well as other intermetallic compounds. We previously found good catalytic properties of Co2FeGe for selective hydrogenation of alkynes and developed nanoparticles of Co2FeGe supported on SiO2. However, the average diameter of the nanoparticles was 23 nm, which is not small enough compared to those of state‐of‐the‐art nanoparticle catalysts. In this study, we developed SiO2‐supported Co2FeGe nanoparticles of <10 nm in diameter. A catalytic test for selective hydrogenation of propyne indicated a partial formation of sites with low selectivity including excess Co atoms. For ammonia decomposition, enhancement of turnover frequency was achieved by reducing the particle size.


Activity switching of Sn and In species in Heusler alloys for electrochemical CO2 reduction
Chemical Communications,58(31):4865-4868 2022
Author:Kazuyuki Iwase; Takayuki Kojima; Naoto Todoroki; Itaru Honma
Abstract:The electrochemical CO2 reduction reaction (CO2RR) activity of Ni2MnIn and Ni2MnSn Heusler alloys was investigated. This is the first report that shows the CO2RR activity of Heusler alloy particles.


High Catalytic Activities of RENi5–xAlx (RE = La, Er) and Low Activity of Mg2Ni Following Hydrogen Uptake: The Role of Absorbed Hydrogen
The Journal of Physical Chemistry C,125(38):20919-20929 2021(Sep. 30)
Author:Ryota Tsukuda; Takayuki Kojima; Ya Xu; Chikashi Nishimura; Marian Krajčí; Satoshi Kameoka


Synthesis of Co2FeGe Heusler alloy nanoparticles and catalysis for selective hydrogenation of propyne
RSC Advances,11(29):18074-18079 2021
Author:Takayuki Kojima; Yuki Nakaya; Hyungwon Ham; Satoshi Kameoka; Shinya Furukawa
Abstract:

Supported nanoparticles of Co2FeGe Heusler alloy were successfully synthesized. The reaction rate per weight was increased 2000 times by nano-sizing.




Durability and activity of Co2YZ (Y = Mn or Fe, Z = Ga or Ge) Heusler alloy catalysts for dehydrogenation of 2-propanol
Catalysis Science & Technology,11(14):4741-4748 2021
Author:Takayuki Kojima; Takuya Koganezaki; Shinpei Fujii; Satoshi Kameoka; An-Pang Tsai
Abstract:

Using dehydrogenation of 2-propanol as a test reaction for Heusler alloy catalysts, durability against oxidation and a relationship between activity and electronic structures were revealed.




Hydrogenation of acetylene and propyne over hydrogen storage ErNi5-Al alloys and the role of absorbed hydrogen
International Journal of Hydrogen Energy,45(38):19226-19236 2020(Jul.)
Author:Ryota Tsukuda; Takayuki Kojima; Daisuke Okuyama; Satoshi Kameoka; Chikashi Nishimura; An-Pang Tsai


Catalytic Properties of Heusler Alloys for Steam Reforming of Methanol
ACS Omega,4(26):21666-21674 2019(Dec.)
Author:T. Kojima; S. Kameoka; A.-P. Tsai


Magnetization reversal, damping properties and magnetic anisotropy of L10-ordered FeNi thin films
Applied Physics Letters,115(20):202402-1-202402-4 2019(Nov.)
Author:V. Thiruvengadam; B.B. Singh; T. Kojima; K. Takanashi; M. Mizuguchi; S. Bedanta


FeNi and Fe16N2 Magnets Prepared Using Leaching
Materials Transactions,60(6):1066-1071 2019(Jun.)
Author:T.Kojima; S. Kameoka; M. Mizuguchi; K. Takanashi; A.-P. Tsai


Catalysis-tunable Heusler alloys in selective hydrogenation of alkynes: A new potential for old materials
Science Advances,4(10):eaat6063 2018(Oct.)
Author:Takayuki Kojima; Satoshi Kameoka; Shinpei Fujii; Shigenori Ueda; An-Pang Tsai; 月プレスリリース


Fabrication of L1(0)-FeNi phase by sputtering with rapid thermal annealing
JOURNAL OF ALLOYS AND COMPOUNDS,750:164-170 2018(Jun.)
Author:Takayuki Tashiro; Masaki Mizuguchi; Takayuki Kojima; Tomoyuki Koganezawa; Masato Kotsugi; Takumi Ohtsuki; Kazuhisa Sato; Toyohiko Konno; Koki Takanashi
Abstract:FeNi films were directly deposited on MgO(001) substrates by co-sputtering and rapid thermal annealing (RTA). The formation of the L1(0) phase was investigated for films with different thicknesses and different annealing conditions by grazing incidence X-ray diffraction. For the FeNi films with a thickness of 5 nm, superlattice 001 and 110 peaks were observed after annealing at a heating rate of 50 degrees C/s, which indicates that three variants of L1(0) grains were formed in the films. The maximum long-range order parameter, which corresponded to a volume-averaged parameter, was approximately 0.11. For the FeNi films with a thickness of 30 nm, a superlattice 110 peak was only observed after annealing at a heating rate of 50 degrees C/s, and the formation of 001 textured grains was clarified. Magnetic properties also changed depending on the FeNi film structures. The formation mechanism of L1(0)-FeNi is discussed based on the strain caused by RTA in the FeNi films. (C) 2018 Elsevier B.V. All rights reserved.


Probing Single Pt Atoms in Complex Intermetallic Al13Fe4
Journal of the American Chemical Society,140(11):3838-3841 2018(Mar. 21)
Author:Tsunetomo Yamada; Takayuki Kojima; Eiji Abe; Satoshi Kameoka; Yumi Murakami; Peter Gille; An Pang Tsai
Abstract:The atomic structure of a 0.2 atom % Pt-doped complex metallic alloy, monoclinic Al13Fe4, was investigated using a single crystal prepared by the Czochralski method. High-angle annular dark-field scanning transmission electron microscopy showed that the Pt atoms were dispersed as single atoms and substituted at Fe sites in Al13Fe4. Single-crystal X-ray structural analysis revealed that the Pt atoms preferentially substitute at Fe(1). Unlike those that have been reported, Pt single atoms in the surface layers showed lower activity and selectivity than those of Al2Pt and bulk Pt for propyne hydrogenation, indicating that the active state of a given single-atom Pt site is strongly dominated by the bonding to surrounding Al atoms.


Creating the hydrogen absorption capability of CeNi5 through the addition of Al
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY,42(34):21832-21840 2017(Aug.)
Author:Ryo Yamagishi; Takayuki Kojima; Satoshi Kameoka; Daisuke Okuyama; Taku J. Sato; Chikashi Nishimura; An-Pang Tsai
Abstract:The hydrogenation capacities of CeNi5-xAlx (x = 0, 0.75, 1.0, 1.25, 1.5 and 1.75) alloys were assessed. In contrast to LaNis-based alloys, the addition of Al to CeNis enables hydrogen absorption by creating larger interstitial sites as the result of an expanded lattice. Structure analyses indicate that each of these alloys maintained a CeNi5 (CaCu5-type) structure in which Al atoms exclusively occupied Ni 3g sites. Among these specimens, CeNi4Al absorbed the greatest proportion of hydrogen atoms, decreasing its c/a ratio from 0.826 to 0.802 upon the formation of CeNi4AlH4.3. This drastic decrease in the c/a ratio is attributed to an anisotropic lattice expansion along the a-axis, as verified by in situ X-ray diffraction under H-2. The enhanced hydrogen absorption of these alloys is thought to be associated with the preferential situation of hydrogen atoms at interstitial sites located at the centers of octagons as well as a charge transition of Ce ions upon hydrogenation. It is verified that CeNi4Al after hydrogenation shows high catalytic activity toward propyne hydrogenation: 100% conversion of propyne even at room temperature. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.


Heusler Alloys: A Group of Novel Catalysts
ACS Omega,2(1):147-153 2017(Jan. 31)
Author:Takayuki Kojima; Satoshi Kameoka; An-Pang Tsai
Abstract:In this study, we investigated the catalytic properties of various Heusler alloys for the hydrogenation of propyne and the oxidation of carbon monoxide. For propyne hydrogenation, Co2FeGe alloy showed a higher activity than that of elemental Co, where neither Fe nor Ge showed any activity. This clearly indicates an alloying effect. For the oxidation of carbon monoxide, although most alloys showed a significant change in catalytic activity during measurement due to an irreversible oxidation of the alloy, Co2TiSn alloy showed a very small change. The results indicate that the catalytic activity and stability of a Heusler alloy can be tuned by employing an appropriate set of elements.


Hydrogenation of Propyne Verifying the Harmony in Surface and Bulk Compositions for Fe-Ni Alloy Nanoparticles
MATERIALS TRANSACTIONS,58(5):768-773 2017
Author:Takayuki Kojima; Shun Fujieda; Genichiro Kato; Satoshi Kameoka; Shigeru Suzuki; An-Pang Tsai
Abstract:We investigated the catalytic properties of Fe1-xNix nanoparticles prepared by a polyol-based method that allowed the precise control of their composition and structure. In the hydrogenation of propyne, the reaction rate decreased with decreasing x, which was in good agreement with the scenario that inactive Fe atoms dilute active Ni ensembles in particles at 0.55 <= x <= 1. For particles with x <= 0.46, it was suggested that slightly active Fe-Ni ensembles mainly contributed to the activity due to small population of active Ni ensembles. Since the change in catalytic properties with x was well explained by the assumption that the surface composition corresponded to x, it was concluded that the surface composition dominating the catalytic properties can be tuned by adjusting the entire composition of nanoparticles.


Growth of L10–FeNi thin films on Cu(001) single crystal substrates using oxygen and gold surfactants
Thin Solid Films,603:348-352 2016(Mar.)
Author:T. Kojima; M. Mizuguchi; K. Takanashi
Abstract:We alternately deposited Ni and Fe monatomic layers on Cu(001) single crystal substrates and also performed surfactant-mediated growth. FeNi films exhibited a large uniaxial magnetic anisotropy (K-u) of over 0.1 MJ/m(3) by using an oxygen or a gold surfactant, although K-u was almost zero without surfactants. Reflection high-energy electron diffraction and atomic force microscopy indicated surfactant effects of oxygen and gold. Synchrotron X-ray diffraction indicated a formation of an L1(o)-type ordered FeNi phase having a large K-u. We have considered that the surfactants enhanced layer-by-layer growth leading to the L1(o)-ordering by changing a diffusion scenario of Fe and Ni atoms. (C) 2016 Elsevier B.V. All rights reserved.


Material dependence of anomalous Nernst effect in perpendicularly magnetized ordered-alloy thin films
APPLIED PHYSICS LETTERS,106(25):252405-1-252405-4 2015(Jun.)
Author:K. Hasegawa; M. Mizuguchi; Y. Sakuraba; T. Kamada; T. Kojima; T. Kubota; S. Mizukami; T. Miyazaki; K. Takanashi
Abstract:Material dependence of the anomalous Nernst effect (ANE) in perpendicularly magnetized ordered-alloy thin films is systematically investigated. The ANE was found to have a tendency to increase simply as uniaxial magnetic anisotropy increased at room temperature. The ANE increases as temperature increases from 10 to 300K for all the materials. However, the signs of the ANE in Fe-based ordered-alloys (L1(0)-FePt and L1(0)-FePd) and in a Co/Ni multilayer are opposite to those in Mn-based ordered-alloys (L1(0)-MnGa and D0(22)-Mn2Ga). Ordered-alloys with larger uniaxial magnetic anisotropies reveal larger ANE and might be desirable for thermoelectric applications. (C) 2015 AIP Publishing LLC.


Local structure and magnetism of L1(0)-type FeNi alloy films with perpendicular magnetic anisotropy studied through Fe-57 nuclear probes
JOURNAL OF PHYSICS D-APPLIED PHYSICS,48(20):205002-1-205002-7 2015(May)
Author:K. Mibu; T. Kojima; M. Mizuguchi; K. Takanashi
Abstract:The local structure and magnetism of FeNi alloy films prepared by alternate deposition of Fe and Ni monatomic layers, where perpendicular magnetic anisotropy has been observed, were investigated through Fe-57 nuclear probes using Mossbauer spectroscopy. It was confirmed that the films are composed of L1(0)-type ordered FeNi phase and A1-type disordered FeNi phase. For the films grown at 40-70 degrees C, which have no perpendicular anisotropy, the A1-disordered phase is dominant, whereas for the films grown at 100-190 degrees C, which have a stronger perpendicular anisotropy, the relative amount of the L1(0)-ordered phase reaches 40% or more. It was clearly shown that the magnetic anisotropy of these films is strongly correlated with the local environments of Fe in the films. The results imply that if a further increase in the ratio of the L1(0)-ordered phase is successfully achieved, one would obtain films with a stronger magnetic anisotropy applicable to perpendicular magnetic recording.


Structural and magnetic properties of FeNi thin films fabricated on amorphous substrates
JOURNAL OF APPLIED PHYSICS,117(17):17E309-1-17E309-3 2015(May)
Author:T. Y. Tashiro; M. Mizuguchi; T. Kojima; T. Koganezawa; M. Kotsugi; T. Ohtsuki; K. Takanashi
Abstract:FeNi films were fabricated by sputtering and rapid thermal annealing on thermally amorphous substrates to realize the formation of an L1(0)-FeNi phase by a simple method. Structural and magnetic properties of FeNi films were investigated by varying the annealing temperature. L1(0)-FeNi superlattice peaks were not observed in X-ray diffraction patterns, indicating no formation of L1(0)-ordered phase, however, the surface structure systematically changed with the annealing temperature. Magnetization curves also revealed a drastic change depending on the annealing temperature, which indicates the close relation between the morphology and magnetic properties of FeNi films fabricated on amorphous substrates. (C) 2015 AIP Publishing LLC.


Structural and Magnetic Depth Profile Analysis of L10 FeNi Film by Polarized Neutron Reflectometry
JPS Conference Proceedings,8:034008-1-034008-6 2015
Author:T. Ueno; K. Saito; N. Inami; T. Kojima; M. Mizuguchi; N. Miyata; K. Akutsu; M. Takeda; K. Takanashi; K. Ono


Addition of Co to L1(0)-ordered FeNi films: influences on magnetic properties and ordered structures
JOURNAL OF PHYSICS D-APPLIED PHYSICS,47(42):425001-1-425001-9 2014(Oct.)
Author:Takayuki Kojima; Masaki Mizuguchi; Tomoyuki Koganezawa; Misako Ogiwara; Masato Kotsugi; Takumi Ohtsuki; Taka-Yuki Tashiro; Koki Takanashi
Abstract:L1(0)-type ordered FeNi alloy is a good candidate material for rare-earth-free permanent magnets due to its large saturation magnetization, large uniaxial magnetic anisotropy (K-u) and high Curie temperature. Previously, we investigated the fundamental properties of L1(0)-FeNi by preparing single crystal films by alternate deposition of Fe and Ni monatomic layers. In the present study, we investigated the influences of the addition of Co on the magnetic and structural properties of L1(0)-type ordered FeNi films. Three types of Co addition, with the substitution of Fe layers, Ni layers and both layers, were performed. X-ray diffraction using synchrotron radiation indicated that Co atoms were randomly distributed in films in all addition processes. A long-range order parameter of the L1(0)-FeNi phase and K-u showed a tendency to decrease with the amount of Co for additions substituting Fe layers and both layers. However, K-u showed no decrease with Co addition substituting <= 10% of Ni layers, even though the order parameter notably decreased. This indicates that an achievement of the Co addition substituting Ni atoms without any reduction of the order parameter enhances K-u in L1(0)-FeNi.


Formation of FeNi with L1(0)-ordered structure using high-pressure torsion
PHILOSOPHICAL MAGAZINE LETTERS,94(10):639-646 2014(Oct.)
Author:Seungwon Lee; Kaveh Edalati; Hideaki Iwaoka; Zenji Horita; Takumi Ohtsuki; Takuo Ohkochi; Masato Kotsugi; Takayuki Kojima; Masaki Mizuguchi; Koki Takanashi
Abstract:FeNi with the L1(0)-ordered structure is formed over an astronomical timescale in meteorites. In this study, severe plastic deformation using high-pressure torsion (HPT) is employed for the production of the L1(0) structure in the laboratory. Its formation is confirmed by X-ray diffraction analysis and transmission electron microscopy. Processing of elemental nanopowders by HPT is an effective method for the formation of the L1(0) phase, which is enhanced by the addition of Co to FeNi or annealing after HPT. The formation of the phase must be associated with enhanced diffusion through HPT.


Detection of spin-resolved electronic structures from a buried ferromagnetic layer utilizing forward Mott scattering
APPLIED PHYSICS LETTERS,104(13):132402 2014(Mar.)
Author:S. Ueda; M. Mizuguchi; T. Kojima; S. Ishimaru; M. Tsujikawa; M. Shirai; K. Takanashi
Abstract:We report ultrahigh-resolution spin-resolved hard X-ray photoemission (HAXPES) for a buried FeNi alloy film. By utilizing the forward Mott scattering in a Au layer on FeNi, our spin-resolved HAXPES method does not require a standard spin detector and allows us to use the multi-channel electron detection system for the high-efficient electron detection as used in conventional photoemission spectroscopy. A combination of the forward Mott scattering and multi-channel detection leads us to measure a clear spin polarization as well as spin-resolved majority and minority states in the Fe 2p core-level spectra without using the standard spin detector. This method enables us to measure spin-resolved core-level spectra for buried ferromagnetic materials. (C) 2014 AIP Publishing LLC.


Fe-Ni composition dependence of magnetic anisotropy in artificially fabricated L1(0)-ordered FeNi films
JOURNAL OF PHYSICS-CONDENSED MATTER,26(6):064207-1-064207-10 2014(Feb.)
Author:Takayuki Kojima; Misako Ogiwara; Masaki Mizuguchi; Masato Kotsugi; Tomoyuki Koganezawa; Takumi Ohtsuki; Taka-Yuki Tashiro; Koki Takanashi
Abstract:We prepared L1(0)-ordered FeNi alloy films by alternate deposition of Fe and Ni monatomic layers, and investigated their magnetic anisotropy. We employed a non-ferromagnetic Au-Cu-Ni buffer layer with a flat surface and good lattice matching to L1(0)-FeNi. An L1(0)-FeNi film grown on Au6Cu51Ni43 showed a large uniaxial magnetic anisotropy energy (K-u = 7.0 x 10(6) erg cm(-3)). K-u monotonically increased with the long-range order parameter ( S) of the L1(0) phase. We investigated the Fe-Ni composition dependence by alternating the deposition of Fe 1 - x and Ni 1 + x monatomic layers ( -0.4 < x < 0.4). Saturation magnetization (M-s) and K-u showed maxima (M-s = 1470 emu cm(-3), K-u = 9.3 x 10(6) erg cm (-3)) for Fe60Ni40 (x = -0.2) while S showed a maximum at the stoichiometric composition (x = 0). The change in the ratio of lattice parameters (c/a) was small for all compositions. We found that enrichment of Fe is very effective to enhance Ku. The large Ms and Ku of Fe60Ni40 indicate that Fe-rich L10-FeNi is promising as a rare-earth-free permanent magnet.


064206Structural, magnetic and electronic state characterization of L1(0)-type ordered FeNi alloy extracted from a natural meteorite
JOURNAL OF PHYSICS-CONDENSED MATTER,26(6):064206-1-064206-6 2014(Feb.)
Author:M. Kotsugi; H. Maruyama; N. Ishimatsu; N. Kawamura; M. Suzuki; M. Mizumaki; K. Osaka; T. Matsumoto; T. Ohkochi; T. Ohtsuki; T. Kojima; M. Mizuguchi; K. Takanashi; Y. Watanabe
Abstract:To understand the hard magnetism of L1(0)-type ordered FeNi alloy, we extracted the L1(0)-FeNi phase from a natural meteorite, and evaluated its fundamental solid-state properties: sample composition, magnetic hysteresis, crystal structure and electronic structure. We executed multidirectional analyses using scanning electron microscopy with an electron probe micro-analyzer (SEM-EPMA), a superconducting quantum interference device (SQUID), x-ray diffraction (XRD) and magnetic circular dichroism (MCD). As a result, we found that the composition was Fe: 50 : 47 +/- 1 : 98 at.%, Ni: 49 : 60 +/- 1 : 49 at.%, and an obvious superlattice peak is confirmed. The estimated degree of order was 0.608, with lattice constants a = b = 3 : 582 angstrom and c = 3 : 607 angstrom. The obtained coercivity was more than 500 Oe. MCD analysis using the K absorption edge suggests that the magnetic anisotropy could originate from the orbital magnetic moment of 3d electrons in Fe; this result is consistent with that in a previous report obtained with synthetic L1(0)-FeNi.


Magnetic domain observation of FeCo thin films fabricated by alternate monoatomic layer deposition
JOURNAL OF APPLIED PHYSICS,115(4):043908-1-043908-5 2014(Jan.)
Author:T. Ohtsuki; T. Kojima; M. Kotsugi; T. Ohkochi; M. Mizuguchi; K. Takanashi
Abstract:FeCo thin films are fabricated by alternate monoatomic layer deposition method on a Cu3Au buffer layer, which in-plane lattice constant is very close to the predicted value to obtain a large magnetic anisotropy constant. The variation of the in-plane lattice constant during the deposition process is investigated by reflection high-energy electron diffraction. The magnetic domain images are also observed by a photoelectron emission microscope in order to microscopically understand the magnetic structure. As a result, element-specific magnetic domain images show that Fe and Co magnetic moments align parallel. A series of images obtained with various azimuth reveal that the FeCo thin films show fourfold in-plane magnetic anisotropy along < 110 > direction, and that the magnetic domain structure is composed only of 90 degrees wall. (C) 2014 AIP Publishing LLC.


Significant surface flattening effect by Au addition for Cu growth on Cu3Au(001)
SURFACE SCIENCE,619:44-48 2014(Jan.)
Author:Takayuki Kojima; Masaki Mizuguchi; Koki Takanashi
Abstract:To prepare a flat surface of Cu film on Cu3Au(001), we utilized the effect of Au addition to Cu, and investigated the dependence of the growth mode on the amount of Au added. We grew Cu-x%Au (x = 0-20) films on Cu3Au(001) underlayers by co-deposition and observed the surface morphology by scanning tunneling microscopy. For Cu film without Au addition, three-dimensional islands were observed on the surface while flat two-dimensional surfaces were observed for Cu film with only 2.5%Au addition. This difference in the growth mode was found to be due to surface segregation of Au revealed by in situ Auger electron spectroscopy. It was considered that the Au atoms acted like a surfactant and avoided three-dimensional island growth by suppression of the accumulation of epitaxial strain in Cu-x%Au films. However, the terrace size decreased with x. This decrease was thought to be due to an increase in an effective Ehrlich-Schwoebel barrier. The surface flattening effect by addition of another element would be obtained in other systems as well by employing a suitable element. (C) 2013 Elsevier B.V. All rights reserved.


Magnetization damping of an L1(0)-FeNi thin film with perpendicular magnetic anisotropy
APPLIED PHYSICS LETTERS,103(24):242409-1-242409-5 2013(Dec.)
Author:Misako Ogiwara; Satoshi Iihama; Takeshi Seki; Takayuki Kojima; Shigemi Mizukami; Masaki Mizuguchi; Koki Takanashi
Abstract:We studied on the magnetic damping constants (alpha) for L1(0)-FeNi and disordered FeNi employing three kinds of measurement methods. An L1(0)-FeNi thin film exhibited high perpendicular magnetic anisotropy of 7.1 x 10(6) erg cm(-3). At magnetic fields (H) lower than 2 kOe, alpha was estimated to be 0.091 +/- 0.003. However, it was reduced down to 0.013 +/- 0.001 with H, indicating that extrinsic contributions enhance alpha. The intrinsic alpha = 0.013 +/- 0.001 was comparable to alpha = 0.009 +/- 0.002 for the disordered FeNi. This suggests that L1(0)-FeNi is a candidate achieving high magnetic anisotropy and low magnetization damping simultaneously. (C) 2013 AIP Publishing LLC.


Origin of strong magnetic anisotropy in L1(0)-FeNi probed by angular-dependent magnetic circular dichroism
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS,326:235-239 2013(Jan.)
Author:Masato Kotsugi; Masaki Mizuguchi; Shigeki Sekiya; Masaichiro Mizumaki; Takayuki Kojima; Tetsuya Nakamura; Hitoshi Osawa; Kenji Kodama; Takumi Ohtsuki; Takuo Ohkochi; Koki Takanashi; Yoshio Watanabe
Abstract:We investigated the origin of strong magnetic anisotropy energy (MAE) in L1(0)-type ordered FeNi phase by angular-dependent magnetic circular dichroism. Our findings showed that the orbital magnetic moment of Fe has a significant angular dependence that exhibits a maximum value at the [001] direction corresponding perpendicular to the plane. The calculated uniaxial anisotropy energy when considering spin-orbit (SO) interaction shows quantitatively good agreement with the volume MAE. We concluded that the orbital anisotropy in 3d Fe electrons results in the strong MAE in L1(0)-FeNi and ascribe this to the spin-orbit interaction via structural ordering. (C) 2012 Elsevier BY. All rights reserved.


Fabrication of fully-epitaxial co-{{{2}}}mnsi/ag/co-{{{2}}}mnsi giant magnetoresistive devices by elevated temperature deposition
IEEE Transactions on Magnetics,49(11):5464-5468 2013
Author:Yuya Sakuraba; Kennosuke Izumi; Tomoyuki Koganezawa; Subrojati Bosu; Ryo Okura; Masaki Ueda; Takayuki Kojima; Kesami Saito; Koki Takanashi
Abstract:(001)-oriented epitaxial Co-{{2}}MnSi (CMS) films were grown by elevating the substrate temperature during deposition instead of a conventional post-annealing process. The CMS film deposited at 250\\circ C showed a very flat surface morphology, large saturation magnetization, and a highly {\\rm L2}-{{1}}-ordered crystal structure. A CMS/Ag/CMS giant-magnetoresistive device with CMS layers grown at 250\\circ C showed the high magnetoresistance ratio (33%) at room temperature. This ratio was close to that realized in the case of samples fabricated using post-annealing at 500-550 \\circ C. The elevated temperature deposition for the Heusler electrodes is a promising method to fabricate a practical magnetic read sensor for next generation hard disc drives without high temperature annealing process over 300\\circC. © 2013 IEEE.


Magnetic Anisotropy and Chemical Order of Artificially Synthesized L1(0)-Ordered FeNi Films on Au-Cu-Ni Buffer Layers
JAPANESE JOURNAL OF APPLIED PHYSICS,51(1) 2012(Jan.)
Author:Takayuki Kojima; Masaki Mizuguchi; Tomoyuki Koganezawa; Keiichi Osaka; Masato Kotsugi; Koki Takanashi
Abstract:L1(0)-FeNi films were grown by alternate monatomic layer deposition on Au-Cu-Ni buffer layers at several substrate temperatures (T-s), and the relation between the uniaxial magnetic anisotropy energy (K-u) and the long-range chemical order parameter (S) was investigated. A large K-u of (7.0 +/- 0.2) x 10(6) erg/cm(3) and S of 0.48 +/- 0.05 were obtained. The value of K-u was larger than those reported previously for artificially synthesized FeNi films. It was first found that both K-u and S increased with T-s, and K-u was roughly proportional to S. (C) 2012 The Japan Society of Applied Physics


Artificial Fabrication and Order Parameter Estimation of L10-ordered FeNi Thin Film Grown on a AuNi Buffer Layer
Journal of the Magnetics Society of Japan,35(4):370-373 2011
Author:M. Mizuguchi; T. Kojima; M. Kotsugi; T. Koganezawa; K. Osaka; K. Takanashi
Abstract:Epitaxial L10-ordered FeNi thin films were artificially fabricated on a nonmagnetic AuNi buffer layer by using an alternate monatomic layer deposition. A uniaxial magnetic anisotropy energy of the FeNi layer was estimated to be 5.8 × 106 erg/cm3 from magnetization measurements, which is the largest energy among values reported on FeNi thin films grown on nonmagnetic buffers. A long-range order parameter of the FeNi layer was estimated to be 0.330 from a grazing incidence X-ray diffraction (GI-XRD) using synchrotron radiation. We also investigated the relation between the ratio of c-axis lattice constant to a-axis lattice constant (c/a ratio) and the uniaxial magnetic anisotropy energy of FeNi thin films grown on several buffer layers. The uniaxial magnetic anisotropy energy monotonically increased with the increase in the c/a ratio, whereas the anisotropy had no clear relation with the long-range order parameter. Not only the improved long-range order parameter but optimized c/a ratio in FeNi are expected to lead to the enhancement of the perpendicular magnetic anisotropy.


Determination of local magnetic moment in L1(0)-FeNi using photoelectron emission microscopy (PEEM)
Journal of Physics: Conference Series,266(1) 2011
Author:Masato Kotsugi; Masaki Mizuguchi; Shigeki Sekiya; Takuo Ohkouchi; Takayuki Kojima; Koki Takanashi; Yoshio Watanabe
Abstract:Magnetic domain structure of L1(0)-type FeNi is observed by angular dependent photoelectron emission microscopy. It reveals the perpendicular magnetic component in magnetic domain structure with Bloch wall. The formation of Bloch wall is ascribed to the large magnetic anisotropy energy of L1(0)-FeNi.


L1(0)-ordered FeNi film grown on Cu-Ni binary buffer layer
Journal of Physics: Conference Series,266(1) 2011
Author:T. Kojima; M. Mizuguchi; K. Takanashi
Abstract:An FeNi film with a metastable L1(0)-ordered phase was fabricated by an alternate monatomic layer deposition. An Fe monolayer and a Ni monolayer were alternately grown on a Cu0.6Ni0.4 binary buffer layer. A (001) L1(0)-FeNi superlattice peak, which indicates the formation of a L1(0) phase, was clearly observed by an X-ray diffraction. A long-range order parameter S of L1(0)-FeNi was estimated to be 0.5 +/- 0.1. It was found that the film has a uniaxial magnetic anisotropy along c-axis by magnetization measurement. The uniaxial magnetic anisotropy energy K-u was evaluated to be (5.0 +/- 0.1) x 10(6) erg/cc.


Growth and Characterization of Ultrathin Fe Films on Molecule-Adsorbed MgO Surfaces
MATERIALS TRANSACTIONS,50(11):2512-2514 2009(Nov.)
Author:Takayuki Kojima; Masaki Mizuguchi; Kohei Oka; Seiji Mitani; Koki Takanashi
Abstract:Effects of the molecule-adsorption on a MgO surface on the growth of ultra-thin Fe films were investigated. Surface observation by reflection high-energy electron diffraction and ultra-high vacuum atomic force microscopy showed that the adsorption of molecules on the MgO surface affected the morphology of Fe films grown on the MgO surface. It was revealed that the surface flatness of Fe films was improved by appropriate molecule-adsorption on the MgO surface. [doi: 10.2320/matertrans.M2009218]


MISC
ホイスラー合金の触媒としての性質
応用物理,91(6):346-350 2022(Jun.)
Author:小嶋隆幸


三元金属間化合物群「ホイスラー合金」の触媒機能
触媒,64(2):92-98 2022(Apr.)
Author:小嶋隆幸


Properties of Heusler alloys as catalysts
JSAP Review 2022
Author:Takayuki Kojima


ホイスラー合金の触媒への応用
まぐね,16(5):224-232 2021(Oct.)
Author:小嶋隆幸


ボールミルによる担持金属ナノ粒子合成
触媒,63(4):248-248 2021(Aug.)
Author:小嶋 隆幸


Screening of Ternary Intermetallic Catalysts Is Possible Using Metallurgical Synthesis: Demonstration on Heusler Alloys
KONA Powder and Particle Journal,38:110-121 2021(Jan. 10)
Author:Takayuki Kojima; Satoshi Kameoka; An-Pang Tsai


ホイスラー合金の応用による貴金属フリー触媒の発見および触媒機能チューニング
翠巒,34:5-5 2020(Jan.)
Author:小嶋 隆幸


三元金属間化合物「ホイスラー合金」の触媒特性
まてりあ,59(7):354-360 2020
Author:小嶋 隆幸


異分野融合による新規触媒の発見 貴金属の代替と触媒機能のメカニズム解明に期待
JETI,67(5):41-43 2019
Author:小嶋隆幸


The emergence of Heusler alloy catalysts
Science and Technology of Advanced Materials,20(1):445-455 2019
Author:T.Kojima; S. Kameoka; A.-P. Tsai


磁性材料研究から触媒研究への挑戦~触媒分野参入の手引き~
まてりあ,57(5):224‐229(J‐STAGE) 2018(May)
Author:小嶋隆幸


Fabrication and characterization of L1(0)-ordered FeNi thin films
JOURNAL OF PHYSICS D-APPLIED PHYSICS,50(48):483002–1-483002–9 2017(Dec.)
Author:Koki Takanashi; Masaki Mizuguchi; Takayuki Kojima; Takayuki Tashiro
Abstract:L1(0)-ordered FeNi, showing high uniaxial magnetic anisotropy (K-u), is promising as a 'rare metal-free' high K-u material. We have worked on L1(0)-ordered FeNi thin films prepared by two methods: one is molecular beam epitaxy (MBE) with alternate deposition of Fe and Ni monatomic layers, and the other is sputtering with co-deposition or multilayer-deposition of Fe and Ni followed by rapid thermal annealing (RTA). For the MBE films prepared by alternate monatomic layer deposition (leading to the stoichiometric composition: Fe 50 at.%-Ni 50 at.%), a clear relationship between K-u and the long-range order parameter S estimated by synchrotron x-ray diffraction (XRD) was found with maximum values of S = 0.48 and K-u = 7.0 x 10(6) erg cm(-3). The composition dependence of K-u was also investigated by deviating the thickness from monatomic layer, showing a maximum of 9.3 x 10(6) erg cm(-3) around 60 at.% Fe. In addition, the effect of Co addition to L1(0)-ordered FeNi was investigated, suggesting that a small amount (< 10 at.%) of Co substitution for Ni would enhance K-u if S keeps the same. The experiments were in qualitatively good agreement with the first-principles calculations. The magnetic damping constant a was also measured to be approximately 0.01 irrespective of S, suggesting that L1(0)-FeNi is a candidate material with high K-u and low a. For the sputtered films with RTA, no major difference between co-deposition and multilayer-deposition was found: in both cases the formation of L1(0)-ordered phase after RTA was definitely confirmed by XRD. Transmission electron microscopy observations indicated that nanometer-sized L1(0)-ordered clusters were dispersed in a disordered phase, in contrast to that of MBE films showing the homogeneous formation of L1(0)-ordered phase. The enhancement of coercivity (H-c) and residual magnetization (M-r/M-s) was observed associated with the appearance of L1(0)-ordered phase. The maxima of H-c and M-r/M-s were obtained to be 1.35 kOe and 0.22, respectively.


単原子交互積層法による新規磁気異方性材料L10-FeNi薄膜の作製と特性評価
まぐね,12(1):13-20 2017(Feb. 01)
Author:水口将輝; 小嶋隆幸; 田代敬之; 高梨弘毅


Hydrogenation of Propyne Verifying the Harmony in Surface and Bulk Compositions for Fe-Ni Alloy Nanoparticles (vol 58, pg 776, 2017)
MATERIALS TRANSACTIONS,58(5):845-845 2017
Author:Takayuki Kojima; Shun Fujieda; Genichiro Kato; Satoshi Kameoka; Shigeru Suzuki; An-Pang Tsai


Artificial fabrication and characterization of L1(0)-ordered FeNi thin films.
2015 IEEE MAGNETICS CONFERENCE (INTERMAG) 2015
Author:K. Takanashi; M. Mizuguchi; T. Kojima; T. Tashiro


スパッタ法によるMgO(001)単結晶基板上へのL10-FeNi規則合金薄膜の作製
日本金属学会講演概要(CD-ROM),154th 2014
Author:田代敬之; 田代敬之; 水口将輝; 小嶋隆幸; 佐藤和久; 今野豊彦; 高梨弘毅; 小金澤智之; 小嗣真人; 大槻匠


高い磁気異方性を有するL10型FePtおよびL10型FeNi規則合金薄膜
セラミックス,48(5):404-409 2013
Author:小嶋隆幸; 関剛斎; 水口将輝; 高梨弘毅


L10型FeNi規則合金(tetrataenite)の磁気異方性
日本金属学会講演概要(CD-ROM),153rd 2013
Author:小嶋隆幸; 荻原美沙子; 水口将輝; 田代敬之; 高梨弘毅; 小嗣真人; 小金澤智之; 大槻匠


貴金属フリー垂直磁気異方性材料「L10型FeNi」
日本磁気学会 第185回研究会資料,:17-21 2012
Author:水口将輝; 小嶋隆幸; 荻原美沙子; 高梨弘毅


人工合成L10型FeNi薄膜の磁気異方性と構造
日本金属学会講演概要(CD-ROM),151st 2012
Author:小嶋隆幸; 荻原美沙子; 水口将輝; 高梨弘毅; 小嗣真人; 小金澤智之; 大槻匠


単原子層制御交互蒸着により作製したL10型FeNi規則合金薄膜の磁気異方性
表面科学学術講演会講演要旨集,32nd 2012
Author:小嶋隆幸; 荻原美沙子; 水口将輝; 田代敬之; 高梨弘毅; 小嗣真人; 小金澤智之; 大槻匠; 大河内拓雄


貴金属フリー高磁気異方性材料L10型FeNi規則合金の作製と評価
まてりあ,50(9):389-392 2011
Author:水口将輝; 小嶋隆幸; 高梨弘毅; 小嗣真人; 白井正文


L10型FeNi薄膜の創製とその特性評価
日本磁気学会 第177回研究会資料,:13-17 2011
Author:水口将輝; 小嶋隆幸; 関谷茂樹; 高梨弘毅


単原子層交互積層法により作製したL10型FeNi薄膜の構造と磁気特性の関係
日本金属学会講演概要(CD-ROM),149th 2011
Author:小嶋隆幸; 小嶋隆幸; 小嶋隆幸; 水口将輝; 小金澤智之; 大坂恵一; 小嗣真人; 高梨弘毅


人工合成L10型FeNi薄膜の規則度評価および磁気異方性との関係
日本金属学会講演概要,148th 2011
Author:小嶋隆幸; 小嶋隆幸; 水口将輝; 小金澤智之; 大坂恵一; 小嗣真人; 高梨弘毅


21aGC-5 単原子層交互積層法によるL1_0型FeNi合金薄膜の人工合成(21aGC 微小領域磁性(薄膜,人工格子,ナノ粒子),領域3(磁性,磁気共鳴))
日本物理学会講演概要集,65(1):470-470 2010(Mar. 01)
Author:水口 将輝; 小嶋 隆幸; 高梨 弘毅


L10型FeNi規則合金の創製および規則度と磁気特性の相関
日本磁気学会学術講演概要集,34th 2010
Author:水口将輝; 小嶋隆幸; 高梨弘毅; 小金澤智之; 大坂恵一; 小嗣真人


単原子層交互積層法により作製したL10型FeNi規則合金の結晶構造解析
日本物理学会講演概要集,65(2) 2010
Author:水口将輝; 小嶋隆幸; 高梨弘毅; 小金澤智之; 大坂恵一; 小嗣真人; 渡辺義夫

研究費
共同研究
2020 - 2020 , 令和2年度北海道大学触媒科学研究所共同利用・共同研究(提案型)

科学研究費補助金(研究代表者)
2019 - 2022 , ホイスラー合金の触媒機能のメカニズム解明 , 基盤研究(B)
2017 - 2019 , 触媒調製技術の応用による希少元素フリー磁石材料の創製 , 若手研究(B)
2014 - 2016 , 磁性金属の価電子スピンと触媒機能の関係の解明 , 研究活動スタート支援

その他公的資金
2018 - 2019 , 領域創成研究プログラム
2015 - 2015 , 多元研プロジェクト
2012 - 2012 , SPring-8 萌芽的研究支援課題 2012A期
2012 - 2012 , SPring-8 萌芽的研究支援課題 2012B期
2011 - 2012 , 特別研究員奨励費

その他
2019 - 2010 , 学術・研究助成
2018 - 2018 , 若手研究者の海外渡航費用助成
2018 - 2018 , 岩谷科学技術研究助成
2018 - 2018 , 野口遵研究助成金
2017 - 2018 , 工学研究奨励援助金
2015 - 2016 , 研究助成