研究者詳細

顔写真

ロイ　トウフアン
Roy Tufan
Roy Tufan
所属
高等研究機構先端スピントロニクス研究開発センター　スピントロニクス材料研究グループ
職名
助教
学位

  • Ｐｈ．Ｄ．（Homi Bhabha National Institute）

  • Ｍ．Ｓ．（The University of Burdwan）

経歴 4

  • 2022年11月 ～ 継続中
    東北大学　先端スピントロニクス研究開発センター

  • 2021年7月 ～ 2022年10月
    東北大学

  • 2018年5月 ～ 2021年6月
    東北大学

  • 2017年10月 ～ 2018年3月
    Raja Ramanna Centre for Advanced Technology, Indore, India

学歴 3

  • Raja Ramanna Centre for Advanced Technology, Indore, India　Doctorate

    2012年 ～ 2017年

  • The University of Burdwan, India　Master of Science

    2010年 ～ 2012年

  • The University of Burdwan, Burdwan Raj College, India　Bachelor of Science

    2007年 ～ 2010年

委員歴 1

  • The Japan Society of Applied Physics　The Japan Society of Applied Physics

    2020年7月 ～ 継続中

研究キーワード 1

  • First-principles calculations, Heusler alloy, Shape memory property, Magnetic Tunnel Junction, Spintronics

研究分野 1

  • ナノテク・材料 / 金属材料物性 /

論文 31

  1. Machine learning for the development of new materials for a magnetic tunnel junction

    Atsufumi Hirohata, Hiroki Koizumi, Tufan Roy, Masahito Tsujikawa, Shigemi Mizukami, Kenji Nawa, Masafumi Shirai

    npj Spintronics　3　(1)　2025年7月30日

    出版者・発行元： Springer Science and Business Media LLC

    DOI： 10.1038/s44306-025-00094-z 　

    eISSN：2948-2119

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    Abstract In materials science, we have been increasing the number of constituent elements in an alloy and compounds to improve their properties. For example, in magnetism and spintronics, ternary alloys, such as NdFeB and CoFeB have been developed and widely used in permanent magnets and memories/sensors, respectively. It has now been considered to be a time to add more elements to further explore their horizon. For such a complicated development, a manual systematic study is no longer practical, leading to the utilisation of machine learning to predict a candidate. These candidates can then be additionally screened by ab initio calculations before experimental confirmation, which can be performed routinely. Additional use of quantum annealing may also broaden the adoptability of machine learning on the materials development. In this perspective, we plan to offer a standardised process for such a development with some requirements for improvement.

  2. Low-moment semiconducting properties of quaternary Heusler alloy CoRuTiSn

    Ravinder Kumar, Tufan Roy, Masafumi Shirai, Sachin Gupta

    Journal of Alloys and Compounds　1026　180530-180530　2025年5月

    出版者・発行元： Elsevier BV

    DOI： 10.1016/j.jallcom.2025.180530 　

    ISSN：0925-8388

  3. Strong antiferromagnetic interlayer exchange coupling induced by small additions of Re to an Ir interlayer in synthetic antiferromagnetic systems

    Yoshiaki Saito, Tufan Roy, Shoji Ikeda, Masafumi Shirai, Hiroaki Honjo, Hirofumi Inoue, Tetsuo Endoh

    Scientific Reports　15　(1)　2025年3月15日

    出版者・発行元： Springer Science and Business Media LLC

    DOI： 10.1038/s41598-025-94088-w 　

    eISSN：2045-2322

  4. Metastable body-centered cubic CoMnFe alloy films with perpendicular magnetic anisotropy for spintronics memory

    Deepak Kumar, Mio Ishibashi, Tufan Roy, Masahito Tsujikawa, Masafumi Shirai, Shigemi Mizukami

    Science and Technology of Advanced Materials　2024年11月13日

    出版者・発行元： Informa UK Limited

    DOI： 10.1080/14686996.2024.2421746 　

    ISSN：1468-6996

    eISSN：1878-5514

  5. Ballistic spin-transport properties of magnetic tunnel junctions with MnCr-based ferrimagnetic quaternary Heusler alloys

    Tufan Roy, Masahito Tsujikawa, Masafumi Shirai

    Physical Review Materials　7　(10)　2023年10月25日

    出版者・発行元： American Physical Society (APS)

    DOI： 10.1103/physrevmaterials.7.104410 　

    eISSN：2475-9953

  6. Anisotropic magnetism and electronic structure of trigonal EuAl2Ge2 single crystals

    Santanu Pakhira, Asish K. Kundu, Farhan Islam, M. A. Tanatar, Tufan Roy, Thomas Heitmann, T. Yilmaz, E. Vescovo, Masahito Tsujikawa, Masafumi Shirai, R. Prozorov, David Vaknin, D. C. Johnston

    Physical Review B　107　(13)　2023年4月28日

    出版者・発行元： American Physical Society (APS)

    DOI： 10.1103/physrevb.107.134439 　

    ISSN：2469-9950

    eISSN：2469-9969

  7. Electronic and magnetic properties of the topological semimetal SmMg2Bi2

    Asish K. Kundu, Santanu Pakhira, Tufan Roy, T. Yilmaz, Masahito Tsujikawa, Masafumi Shirai, E. Vescovo, D. C. Johnston, Abhay N. Pasupathy, Tonica Valla

    Physical Review B　106　(24)　2022年12月19日

    出版者・発行元： American Physical Society (APS)

    DOI： 10.1103/physrevb.106.245131 　

    ISSN：2469-9950

    eISSN：2469-9969

  8. Topological electronic structure of YbMg2Bi2 and CaMg2Bi2

    Asish K. Kundu, Tufan Roy, Santanu Pakhira, Ze-Bin Wu, Masahito Tsujikawa, Masafumi Shirai, D. C. Johnston, Abhay N. Pasupathy, Tonica Valla

    npj Quantum Materials　7　(1)　2022年6月23日

    出版者・発行元： Springer Science and Business Media LLC

    DOI： 10.1038/s41535-022-00474-2 　

    eISSN：2397-4648

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    Abstract Zintl compounds have been extensively studied for their outstanding thermoelectric properties, but their electronic structure remains largely unexplored. Here, we present a detailed investigation of the electronic structure of the isostructural thermopower materials YbMg2Bi2 and CaMg2Bi2 using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT). The ARPES results show a significantly smaller Fermi surface and Fermi velocity in CaMg2Bi2 than in YbMg2Bi2. Our ARPES results also reveal that in the case of YbMg2Bi2, Yb-4f states reside well below the Fermi level and likely have a negligible impact on transport properties. To properly model the position of 4f-states, as well as the overall electronic structure, a Hubbard U at the Yb sites and spin-orbit coupling (SOC) have to be included in the DFT calculations. The theoretical results reveal that both materials belong to a Z2 topological class and host topological surface states around EF. Due to the intrinsic hole doping, the topological states reside above the Fermi level, inaccessible by ARPES. Our results also suggest that in addition to SOC, vacancies and the resulting hole doping play an important role in the transport properties of these materials.

  9. Structure and magnetism in metastable bcc Co1−xMnx epitaxial films 査読有り

    Kazuma Kunimatsu, Tufan Roy, Jun Okabayashi, Tomoki Tsuchiya, Tomohiro Ichinose, Masahito Tsujikawa, Masafumi Shirai, Shigemi Mizukami

    Journal of Magnetism and Magnetic Materials　548　168841-168841　2022年4月

    DOI： 10.1016/j.jmmm.2021.168841 　

    ISSN：0304-8853

    eISSN：1873-4766

  10. IrCrMnZ (Z = Al, Ga, Si, Ge) Heusler alloys as electrode materials for MgO-based magnetic tunneling junctions: a first-principles study 査読有り

    Tufan Roy, Masahito Tsujikawa, Masafumi Shirai

    Journal of Physics D: Applied Physics　55　(12)　125303-125303　2022年3月24日

    出版者・発行元： {IOP} Publishing

    DOI： 10.1088/1361-6463/ac3dab 　

    ISSN：0022-3727 1361-6463

    eISSN：1361-6463

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    <title>Abstract</title> We study IrCrMnZ (Z=Al, Ga, Si, Ge) systems using first-principles calculations from the perspective of their application as the electrode materials of MgO-based MTJs. These materials have highly spin-polarized conduction electrons with partially occupied Δ1 band, which is important for coherent tunneling in parallel magnetization configuration. The Curie temperatures of IrCrMnAl and IrCrMnGa are very high (above 1300 K) as predicted from mean-field-approximation. The stability of ordered phase against various antisite disorders has been investigated. We discuss here the effect of ``spin-orbit-coupling'' on the electronic structure around Fermi level. Further, we investigate the electronic structure of IrCrMnZ/MgO heterojunction along (001) direction. IrCrMnAl/MgO and IrCrMnGa/MgO maintain half-metallicity even at the MgO interface, with no interfacial states at/around Fermi level in the minority-spin channel. Large majority-spin conductance of IrCrMnAl/MgO/IrCrMnAl and IrCrMnGa/MgO/IrCrMnGa is reported from the calculation of ballistic spin-transport property for parallel magnetization configuration. We propose IrCrMnAl/MgO/IrCrMnAl and IrCrMnGa/MgO/IrCrMnGa as promising MTJs with a weaker temperature dependence of tunneling magnetoresistance ratio, owing to their very high Curie temperatures.

  11. Lattice Softening in Metastable bcc CoxMn100−x (001) Ferromagnetic Layers for a Strain-Free Magnetic Tunnel Junction 査読有り

    Kevin Elphick, Kenta Yoshida, Tufan Roy, Tomohiro Ichinose, Kazuma Kunimatsu, Tomoki Tsuchiya, Kazuya Z. Suzuki, Masahito Tsujikawa, Yasuyoshi Nagai, Shigemi Mizukami, Masafumi Shirai, Atsufumi Hirohata

    Physical Review Applied　16　(5)　2021年11月30日

    DOI： 10.1103/physrevapplied.16.054052 　

    ISSN：2331-7019

    eISSN：2331-7019

  12. Structural and magnetic properties of CoIrMnAl equiatomic quaternary Heusler alloy epitaxial films designed using first-principles calculations 査読有り

    Ren Monma, Tufan Roy, Kazuya Suzuki, Tomoki Tsuchiya, Masahito Tsujikawa, Shigemi Mizukami, Masafumi Shirai

    JOURNAL OF ALLOYS AND COMPOUNDS　868　2021年7月

    DOI： 10.1016/j.jallcom.2021.159175 　

    ISSN：0925-8388

    eISSN：1873-4669

  13. Ab initio study of electronic and magnetic properties of Mn(2)RuZ/MgO (001) heterojunctions (Z = Al, Ge) 国際誌 査読有り

    Tufan Roy, Masahito Tsujikawa, Masafumi Shirai

    JOURNAL OF PHYSICS-CONDENSED MATTER　33　(14)　2021年4月

    DOI： 10.1088/1361-648X/abdffc 　

    ISSN：0953-8984

    eISSN：1361-648X

  14. Observation of inverse magnetocaloric effect in magnetic-field-induced austenite phase of Heusler alloys Ni50-xCoxMn31.5Ga18.5 (x=9 and 9.7) OBSERVATION of INVERSE MAGNETOCALORIC EFFECT ... T. KIHARA et AL. 査読有り

    Kihara, T., Roy, T., Xu, X., Miyake, A., Tsujikawa, M., Mitamura, H., Tokunaga, M., Adachi, Y., Eto, T., Kanomata, T.

    Physical Review Materials　5　(3)　2021年3月23日

    出版者・発行元： American Physical Society (APS)

    DOI： 10.1103/PhysRevMaterials.5.034416 　

    ISSN：2475-9953

    eISSN：2475-9953

  15. Magnetic tunnel junctions with metastable bcc Co3Mn electrodes 査読有り

    Kazuma Kunimatsu, Tomoki Tsuchiya, Tufan Roy, Kelvin Elphick, Tomohiro Ichinose, Masahito Tsujikawa, Atsufumi Hirohata, Masafumi Shirai, Shigemi Mizukami

    APPLIED PHYSICS EXPRESS　13　(8)　2020年8月

    ISSN：1882-0778

    eISSN：1882-0786

  16. Experimental inspection of a computationally-designed NiCrMnSi Heusler alloy with high Curie temperature 査読有り

    Onodera, Y., Elphick, K., Kanemura, T., Roy, T., Tsuchiya, T., Tsujikawa, M., Yoshida, K., Nagai, Y., Mizukami, S., Hirohata, A., Shirai, M.

    Japanese Journal of Applied Physics　59　(7)　073003-073003　2020年7月1日

    出版者・発行元： IOP Publishing

    DOI： 10.35848/1347-4065/ab9c75 　

    ISSN：1347-4065 0021-4922

    eISSN：1347-4065

  17. Ab-initio study of electronic and magnetic properties of CoIrMnZ (Z= Al, Si, Ga, Ge) Heusler alloys 査読有り

    Tufan Roy, Masahito Tsujikawa, Takuro Kanemura, Masafumi Shirai

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS　498　2020年3月

    DOI： 10.1016/j.jmmm.2019.166092 　

    ISSN：0304-8853

    eISSN：1873-4766

  18. Electronic structure of Au-Sn compounds grown on Au(111)

    Pampa Sadhukhan, Sajal Barman, Tufan Roy, Vipin Kumar Singh, Shuvam Sarkar, Aparna Chakrabarti, Sudipta Roy Barman

    PHYSICAL REVIEW B　100　(23)　2019年12月

    DOI： 10.1103/PhysRevB.100.235404 　

    ISSN：2469-9950

    eISSN：2469-9969

  19. Magnetic tunnel junctions with a B2-ordered CoFeCrAl equiatomic Heusler alloy

    Tomoki Tsuchiya, Tufan Roy, Kelvin Elphick, Jun Okabayashi, Lakhan Bainsla, Tomohiro Ichinose, Kazuya Z. Suzuki, Masahito Tsujikawa, Masafumi Shirai, Atsufumi Hirohata, Shigemi Mizukami

    PHYSICAL REVIEW MATERIALS　3　(8)　2019年8月

    DOI： 10.1103/PhysRevMaterials.3.084403 　

    ISSN：2475-9953

  20. Ab-initio study of X-ray absorption and X-ray magnetic circular dichroism spectra of Mn2PtGa and Co2PtGa alloys 査読有り

    Tufan Roy, Arup Banerjee, Rajeev Dutt, J. Nayak, M. Maniraj, S. R. Barman, Aparna Chakrabarti

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS　466　143-149　2018年11月

    DOI： 10.1016/j.jmmm.2018.06.082 　

    ISSN：0304-8853

    eISSN：1873-4766

  21. Magnetic interactions and electronic structure of Pt2Mn1-xYxGa (Y = Cr and Fe) system: An ab-initio calculation 査読有り

    Tufan Roy, Aparna Chakrabarti

    PRAMANA-JOURNAL OF PHYSICS　89　(1)　2017年7月

    DOI： 10.1007/s12043-017-1401-4 　

    ISSN：0304-4289

    eISSN：0973-7111

  22. Ab initio study of effect of Co substitution on the magnetic properties of Ni and Pt-based Heusler alloys 査読有り

    Tufan Roy, Aparna Chakrabarti

    PHYSICS LETTERS A　381　(16)　1449-1456　2017年4月

    DOI： 10.1016/j.physleta.2017.02.020 　

    ISSN：0375-9601

    eISSN：1873-2429

  23. Ab initio studies on electronic and magnetic properties of X2PtGa (X=Cr, Mn, Fe, Co) Heusler alloys 査読有り

    Tufan Roy, Aparna Chakrabarti

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS　423　395-404　2017年2月

    DOI： 10.1016/j.jmmm.2016.09.127 　

    ISSN：0304-8853

    eISSN：1873-4766

  24. Study of structural, magnetic and electronic properties of Ni-Fe-Ga based ferromagnetic shape memory alloys

    Madhusmita Baral, Tufan Roy, Balaji Mondal, Aparna Chakrabarti, Tapas Ganguli

    61ST DAE-SOLID STATE PHYSICS SYMPOSIUM　1832　2017年

    DOI： 10.1063/1.4980592 　

    ISSN：0094-243X

  25. Probing the possibility of coexistence of martensite transition and half-metallicity in Ni and Co-based full-Heusler alloys: An ab initio calculation 査読有り

    Tufan Roy, Dhanshree Pandey, Aparna Chakrabarti

    PHYSICAL REVIEW B　93　(18)　2016年5月

    DOI： 10.1103/PhysRevB.93.184102 　

    ISSN：2469-9950

    eISSN：2469-9969

  26. Possibility of martensite transition in Pt-Y-Ga (Y = Cr, Mn, and Fe) system: An ab-initio calculation of the bulk mechanical, electronic and magnetic properties 査読有り

    Tufan Roy, Aparna Chakrabarti

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS　401　929-937　2016年3月

    DOI： 10.1016/j.jmmm.2015.11.001 　

    ISSN：0304-8853

    eISSN：1873-4766

  27. Effect of substitution on elastic stability, electronic structure and magnetic property of Ni-Mn based Heusler alloys: An ab initio comparison 査読有り

    Tufan Roy, Markus E. Gruner, Peter Entel, Aparna Chakrabarti

    JOURNAL OF ALLOYS AND COMPOUNDS　632　822-829　2015年5月

    DOI： 10.1016/j.jallcom.2015.01.255 　

    ISSN：0925-8388

    eISSN：1873-4669

  28. Temperature dependent EXAFS study of chromium-doped GaFeO<inf>3</inf>at gallium and iron edges

    Basu, S., Singh, R., Das, A., Roy, T., Chakrabarti, A., Nigam, A.K., Jha, S.N., Bhattacharyya, D.

    Journal of Physical Chemistry C　119　(4)　2029-2037　2015年1月29日

    出版者・発行元： American Chemical Society (ACS)

    DOI： 10.1021/jp508103x 　

    ISSN：1932-7455 1932-7447

    eISSN：1932-7455

  29. Study of Effect of Copper-Substitution at Ga Site in Some Ga-Based Heusler Alloys from First-Principles Calculations 査読有り

    Tufan Roy, Aparna Chakrabarti

    PROCEEDINGS OF THE 59TH DAE SOLID STATE PHYSICS SYMPOSIUM 2014 (SOLID STATE PHYSICS)　1665　2015年

    DOI： 10.1063/1.4918016 　

    ISSN：0094-243X

  30. Magnetic properties and electronic structure of Mn-Ni-Ga magnetic shape memory alloys 国際誌

    Sunil Wilfred D'Souza, Tufan Roy, Sudipta Roy Barman, Aparna Chakrabarti

    JOURNAL OF PHYSICS-CONDENSED MATTER　26　(50)　506001-506001　2014年12月

    DOI： 10.1088/0953-8984/26/50/506001 　

    ISSN：0953-8984

    eISSN：1361-648X

  31. Ab initio studies of effect of copper substitution on the electronic and magnetic properties of Ni2MnGa and Mn2NiGa

    Aparna Chakrabarti, Mario Siewert, Tufan Roy, Krishnakanta Mondal, Arup Banerjee, Markus E. Gruner, Peter Entel

    PHYSICAL REVIEW B　88　(17)　2013年11月

    DOI： 10.1103/PhysRevB.88.174116 　

    ISSN：2469-9950

    eISSN：2469-9969

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