Yuki K. Wakabayashi

NTT Basic Research Laboratories　Low-Dimensional Nanomaterials Research Group

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    Publication (*: Corresponding author)

    1. Thickness-dependent quantum transport of Weyl fermions in ultra-high-quality SrRuO3 films
      S. Kaneta-Takada, Y. K. Wakabayashi* (co-first), Y. Krockenberger, S. Ohya, M. Tanaka, Y. Taniyasu, and H. Yamamoto
      arXiv:2011.03670
    2. Quantum transport evidence of Weyl fermions in an epitaxial ferromagnetic oxide
      K. Takiguchi, Y. K. Wakabayashi* (co-first), H. Irie, Y. Krockenberger, T. Otsuka, H. Sawada, S. A. Nikolaev, H. Das, M. Tanaka, Y. Taniyasu, and H. Yamamoto
      Nature Communications 11, 4969 (2020).
      (NTT News Release)
    3. Characterization of in-gap states in epitaxial CoFe2O4(111) layers grown on Al2O3(111)/Si(111) by resonant inelastic x-ray scattering
      Y. K. Wakabayashi*, T. Tokushima, K. Kuga, H. Yomosa, M. Oura, H. Fujiwara, T. Ishikawa, M. Tanaka, T. Kiss*, and R. Nakane*
      arXiv:1910.05734
    4. Magnetization process of the insulating ferromagnetic semiconductor (Al,Fe)Sb
      S. Sakamoto, L. D. Anh, P. N. Hai, Y. Takeda, M. Kobayashi, Y. K. Wakabayashi, Y. Nonaka, K. Ikeda, Z. Chi, Y. Wan, M. Suzuki, Y. Saitoh, H. Yamagami, M. Tanaka, and A. Fujimori
      Physical Review B?101, 075204 (2020).
    5. Machine-learning-assisted thin-film growth: Bayesian optimization in molecular beam epitaxy of SrRuO3 thin films
      Y. K. Wakabayashi*, T. Otsuka, Y. Krockenberger, H. Sawada, Y. Taniyasu, and H. Yamamoto
      APL Materials 7, 101114 (2019).
    6. Electronic structure of the high-TC ferromagnetic semiconductor (Ga,Fe)Sb: X-ray magnetic circular dichroism and resonance photoemission spectroscopy studies
      S. Sakamoto, N. T. Tu, Y. Takeda, S.-i. Fujimori, P. N. Hai, L. D. Anh, Y. K. Wakabayashi, G. Shibata, M. Horio, K. Ikeda, Y. Saitoh, H. Yamagami, M. Tanaka, and A. Fujimori
      Physical Review B?100, 035204 (2019).
    7. Ferromagnetism above 1000?K in a highly cation-ordered double-perovskite insulator Sr3OsO6
      Y. K. Wakabayashi*, Y. Krockenberger, N. Tsujimoto, T. Boykin, S. Tsuneyuki, Y. Taniyasu, and H. Yamamoto
      Nature communications 10, 535 (2019). Selected as Editor's Highlights.
      (NTT News Release)
    8. Cation distribution and magnetic properties in ultrathin (Ni1-xCox)Fe2O4 (x = 0 - 1) layers on Si(111) studied by soft x-ray magnetic circular dichroism
      Y. K. Wakabayashi*, Y. Nonaka, Y. Takeda, S. Sakamoto, K. Ikeda, Z. Chi, G. Shibat, A. Tanaka, Y. Saitoh, H. Yamagami, M. Tanaka, A. Fujimori, and R. Nakane*
      Physical Review Materials 2, 104416 (2018).
    9. Improved adaptive sampling method utilizing Gaussian process regression for prediction of spectral peak structures
      Y. K. Wakabayashi*, T. Otsuka*, Y. Taniyasu, H. Yamamoto, and H. Sawada*
      Applied Physics Express 11, 112401 (2018).
    10. Impurity band conduction in group-IV ferromagnetic semiconductor Ge1-xFex with nanoscale fluctuations in Fe concentration
      Y. Ban, Y. K. Wakabayashi, R. Nakane, and M. Tanaka
      Journal of Applied Physics 124, 113902 (2018).
    11. Magnetic states of the weakly ferromagnetic iron-based superconductor Sr2VFeAsO{3-Δ} studied by x-ray magnetic circular dichroism
      M. Horio, Y. Takeda, H. Namiki, T. Katagiri, Y. K. Wakabayashi, S. Sakamoto, Y. Nonaka, G. Shibata, K. Ikeda, Y. Saitoh, H. Yamagami, T. Sasagawa, and A. Fujimori
      Journal of the Physical Society of Japan 87, 105001 (2018).
    12. Quantum size effect in a Fe quantum well detected by resonant tunneling carriers injected from a p-type Ge semiconductor electrode
      R. Suzuki*, Y. K. Wakabayashi, K. Okamoto, M. Tanaka*, and S. Ohya*
      Applied Physics Letters 112, 152402 (2018).
    13. Effects of annealing gas and drain doping concentration on electrical properties of Ge-source/Si-channel heterojunction tunneling FETs
      T.-E. Bae*, Y. Wakabayashi, R. Nakane, M. takenaka, and S. Takagi*
      Japanese Journal of Applied Physics 57, 04FD11 (2018).
    14. Fe concentration dependence of tunneling magnetoresistance in magnetic tunnel junctions using group-IV ferromagnetic semiconductor GeFe
      K. Takiguchi*, Y. K. Wakabayashi, K. Okamoto, M. Tanaka*, and S. Ohya*
      AIP advances 7, 105202 (2017).
    15. Observation of the inverse spin Hall effect in the topological crystalline insulator SnTe using spin pumping
      S.?Ohya*, A. Yamamoto, T. Yamaguchi, R. Ishikawa, R. Akiyama, L.?D.?Anh, S. Goel, Y. K. Wakabayashi, S. Kuroda*, and M. Tanaka*
      Physical Review B?96, 094424 (2017).
    16. Electronic structure and magnetic properties?of magnetically dead layers in epitaxial CoFe2O4/Al2O3/Si(111) films studied by X-ray magnetic circular dichroism
      Y. K. Wakabayashi*, Y. Nonaka, Y. Takeda, S. Sakamoto, K. Ikeda, Z. Chi, G. Shibata, A. Tanaka, Y. Saitoh, H. Yamagami, M. Tanaka, A. Fujimori, and R. Nakane*
      Physical Review B?96, 104410 (2017).
    17. Origin of robust nanoscale ferromagnetism in Fe-doped Ge revealed by angle-resolved photoemission spectroscopy and first-principles calculation
      S. Sakamoto, Y. K. Wakabayashi, Y. Takeda, S.-i Fujimori, H. Suzuki, Y. Ban, H. Yamagami, M. Tanaka, S. Ohya, and A. Fujimori
      Physical Review B 95, 075203 (2017).
    18. Origin of the large positive magnetoresistance in Ge1-xMnx granular thin films
      Y. K. Wakabayashi*, R. Akiyama, Y. Takeda, M. Horio, G. Shibata, S. Sakamoto, Y. Ban, Y. Saitoh, H. Yamagami, A. Fujimori, M. Tanaka, and S. Ohya*
      Physical Review B 95, 014417 (2017).
    19. Tunneling magnetoresistance in trilayer structures composed of group-IV ferromagnetic semiconductor Ge1-xFex, MgO, and Fe
      Y. K. Wakabayashi*, K. Okamoto, ?Y. Ban, S. Sato, M. Tanaka*, and S. Ohya*
      Applied Physics Express 9, 123001 (2016). Selected as Highlights of 2016.
    20. Room-temperature local ferromagnetism and its nanoscale expansion in the ferromagnetic semiconductor Ge1?xFex
      Y. K. Wakabayashi*, S. Sakamoto, Y. Takeda, K. Ishigami, Y. Takahashi, Y. Saitoh, H. Yamagami, A. Fujimori, M. Tanaka*, and S. Ohya*
      Scientific Reports 6, 23295 (2016).
    21. Soft X-ray angle-resolved photoemission with micro-positioning techniques for metallic V2O3
      H. Fujiwara*, T. Kiss, Y. K. Wakabayashi, Y. Nishitani, T. Mori, Y. Nakata, S. Kitayama, K. Fukushima, S. Ikeda, H. Fushimoto, Y. Minowa, S. -K. Mo, J. Denlinger, J. W. Allen, P. Metcalf, M. Imai, K. Yoshimura, S. Suga, T. Muro, and A. Sekiyama
      Journal of Synchrotron Radiation 22 (2015).
    22. Ge/Si Hetero-Junction Tunnel Field-Effect Transistors and Their Post Metallization Annealing Effect
      M. Kim, Y. K. Wakabayashi, M. Yokoyama, R. Nakane, M. Takenaka, and S. Takagi
      IEEE Transactions on Electron Devices 62, 9 (2015).
    23. High Ion/Ioff Ge-source ultrathin body strained-SOI Tunnel FETs
      M. Kim, Y. Wakabayashi, R. Nakane, M. Yokoyama, M. Takenaka, and S. Takagi
      IEEE International Electron Devices Meeting (IEDM) (2014) pp. 331-334.
    24. Annealing-induced enhancement of ferromagnetism and nano-particle formation in the ferromagnetic semiconductor GeFe
      Y. K. Wakabayashi, Y. Ban, S. Ohya, and M. Tanaka
      Physical Review B 90, 205209 (2014).
    25. Important role of the non-uniform Fe distribution for the ferromagnetism in group-IV-based ferromagnetic semiconductor GeFe
      Y. K. Wakabayashi, S. Ohya, Y. Ban, and M. Tanaka
      Journal of Applied Physics 116, 173906 (2014).
    26. Carrier transport properties of the Group-IV ferromagnetic semiconductor Ge1-xFex with and without boron doping
      Y. Ban*, Y. Wakabayashi, R. Akiyama, R. Nakane, and M. Tanaka*
      AIP advances 4, 097108 (2014).

    Review and proceeding

    1. [Review (in Japanese)] Si(111)基板上に作製したCoFe2O4/Al2O3の界面付近の磁性と電子状態の研究
      野中洋亮，若林勇希，芝田悟朗，酒巻真粧子，雨宮健太，田中雅明，中根了昌，藤森淳
      PF News 36, No. 2, 32 (2018).
    2. [proceeding] Performance Improvement of Ge-source/Si-channel Hetero-Junction Tunneling FETs: Effects of Annealing Gas and Drain Doping Concentration
      T. -E. Bae, Y. Wakabayashi, R. Nakane, M. Yokoyama, M. Takenaka and S. Takagi
      Extended Abstracts of the 2013 International Conference on Solid State Devices and Materials, E-3-03?(2017).
    3. [Review (in Japanese)] IV族強磁性半導体GeFeの物性解明と磁気トンネル接合
      Y. K. Wakabayashi
      応用電子物性分科会会誌 22巻4号, 143 (2016).
    4. [Review (in Japanese)] 軟X線角度分解光電子分光による強磁性半導体Ge1-xFexの電子構造の解明
      坂本祥哉，若林勇希，竹田幸治，藤森伸一，鈴木博人，伴芳祐，山上浩志，田中雅明，大矢忍，藤森淳
      放射光　29, No. 2, 104 (2016).
    5. [proceeding (in Japanese)] ゲルマニウムソース薄膜ひずみSOIトンネルFETの実現とその電気特性に与えるひずみ、MOS界面 、バックバイアスの効果
      金 閔洙、若林勇希、中根了昌、横山正史、竹中充、高木信一
      電子情報通信学会技術研究報告. 114, 9-12 (2015).
    6. [proceeding] Electrical Characteristics of Ge/Si Hetero-Junction Tunnel Field-Effect Transistors and their Post Annealing Effects
      M. Kim, Y. Wakabayashi, R. Nakane, M. Yokoyama, M. Takenaka and S. Takagi
      Extended Abstracts of the 2013 International Conference on Solid State Devices and Materials, p624-625 (2013).

    Invited talk

    1. IV族強磁性半導体Ge1-xFexの物性解明と磁気トンネル接合
      Yuki K. Wakabayashi
      応用物理学会応用電子物性分科会・スピントロニクス研究会共催「スピントロニクス材料の新展開」 2016年11月21日
    2. Search for oxide thin films by utilizing statistical machine learning
      Yuki K. Wakabayashi
      The 66th JSAP Spring Meeting Symposium "Present and future on informatics technologies" March 10, 2019
    3. Jeff= 3/2 ferromagnetic insulating state above 1000 K in a double perovskite osmate Sr3OsO6
      Yuki K. Wakabayashi
      The 80th JSAP Autumn Meeting "Young Scientist Presentation Award Speech" September 18, 2019
    4. Molecular beam epitaxy and utilization of machine learning for 4d and 5d ferromagnetic oxides
      Yuki K. Wakabayashi
      The 80th JSAP Autumn Meeting Symposium "New spintronic materials and their physical properties" September 19, 2019
    5. Molecular beam epitaxy and utilization of machine learning for 4d and 5d ferromagnetic perovskites
      Yuki K. Wakabayashi
      CSRN-Tokyo Workshop 2019「スピントロニクス新機能物質と巨大物性応答」 November 23, 2019
    6. Molecular beam epitaxy and utilization of machine learning for development of novel and high-quality 4d and 5d magnetic oxides
      Yuki K. Wakabayashi
      The 29th Annual Meeting of MRS-J "Unconventional physical properties generated from spin textures and its applications" November 28, 2019
    7. Molecular beam epitaxy and utilization of machine learning for development of novel and high-quality 4d and 5d magnetic oxides
      Yuki K. Wakabayashi
      122nd Tokyo Institute of Technology MSL Lecture, February 28, 2020
    8. Molecular beam epitaxy and utilization of machine learning for development of novel and high-quality 4d and 5d magnetic oxides
      Yuki K. Wakabayashi
      日本磁気学会 第76回スピントロニクス専門研究会 2020年9月25日
    9. Machine-learning-assisted molecular beam epitaxy for growth of high-quality magnetic oxides
      Yuki K. Wakabayashi
      応用物理学会薄膜表面表面物理分科会「情報データ科学に基づく結晶材料・界面・プロセス工学の新展開」 2020年11月13日
    10. Machine-learning-assisted molecular beam epitaxy for growth of high-quality magnetic oxides
      Yuki K. Wakabayashi
      日本学術振興会プラズマ材料科学第153委員会「機械学習を利用したプラズマ材料プロセッシング」 2020年12月18日