Research Interest

Broad research area:  Experimental Condensed Matter Physics - Applied Physics & Materials Science

Research Topics (Including but not limited to):

• Magnetism & application of magnetic materials

• Thin films, magnetic multilayers, nanocomposites, hybrid nanostructures

• Development of magnetic thermal energy harvesting and management materials & application research

• Transverse thermoelectric generation, wearable thermoelectric devices

• Fundamental and technology research on spin- and thermo-spin-transport-based sensors and devices 

• Magneto-thermal switching in thin film and bulk structures

• Ferromagnetic resonance

• Magnetic refrigeration technology for everyday use, including Hydrogen liquefaction

Research Keywords: Spin Caloritronics, Spintronics, Magnetocalorics, Heusler alloy, Ferromagnetic Resonance

Intellectual property / Patent

1) 特願2021-160834 「熱電体及び多層熱電体、並びにこれを用いた曲げられる熱電発電機／熱流センサ」; 内田健一、モダック ラージクマール、桜庭裕弥、周偉男、セペリ アミン ホセイン [International Patent Application No. PCT/JP2022/036432 "Thermoelectric body, thermoelectric generation element, multilayer thermoelectric body, multilayer thermoelectric generation element, thermoelectric generator, and heat flow sensor", Uchida Kenichi, Modak Rajkumar, Sakuraba Yuya , Zhou  Weinan, Hossein Seperi Amin] (Publication No. WO2023054583A1)

Journal Publications

32) Takamasa Hirai, Toshiaki Morita, Subrata Biswas, Jun Uzuhashi, Takashi Yagi, Yuichiro Yamashita, Varun Kumar Kushwaha, Fuya Makino, Rajkumar Modak, Yuya Sakuraba, Tadakatsu Ohkubo, Rulei Guo, Bin Xu, Junichiro Shiomi, Daichi Chiba, and Ken-ichi Uchida, Nonequilibrium Magnonic thermal transport engineering, (2024). (Under review) arXiv:2403.04166

31) Rajkumar Modak, Takamasa Hirai, Yuya Sakuraba, Seiji Mitani, Koichi Oyanagi, Takumi Yamazaki, Takeshi Seki, and Ken-ichi Uchida, High-throughput optimization of magnetoresistance materials based on lock-in thermography, (2024). (Under review)

30) Rajkumar Modak, Takamasa Hirai, Seiji Mitani, and Ken-ichi Uchida, Observation of the Anisotropic Magneto-Thomson Effect, Physical Review Letters 131, 206701 (2023).

29) Rajkumar Modak,Weinan Zhou,Yuya Sakuraba, and Ken-ichi Uchida, Comparison of the in-plane coercive field and anomalous Nernst effect between a co-sputtered Sm-Co amorphous film and Sm/Co multilayer amorphous films with various layer thicknesses, Applied Physics Express 16, 053003 (2023).

28) Hiroto Masuda, Yuta Yamane, Takeshi Seki, Klaus Raab, Takaaki Dohi, Rajkumar Modak, Ken-ichi Uchida, Junichi Ieda, Mathias Kläui, and Koki Takanashi, Magnetization switching process by dual spin-orbit torque in interlayer exchange-coupled systems, Applied Physics Letters 122, 162402 (2023).

27) R. Modak, Y. Sakuraba, T. Hirai, T. Yagi, H. Sepehri-Amin, W. Zhou, H. Masuda, T. Seki, K. Takanashi, T. Ohkubo, and K. Uchida, Sm-Co-based amorphous alloy films for zero-field operation of transverse thermoelectric generation, Science and Technology of Advanced Materials 23,767 (2022). arXiv:2203.10737

26) Naoki Chiba, Satoshi ISHII, Rajkumar Modak, and Ken-ichi Uchida, Single-material-based anomalous Nernst thermopile driven by solar heating and radiative cooling, Applied Physics Express 15, 093001 (2022) Featured as IoP "Spotlights"

25) Ren Nagasawa, Koichi Oyanagi, Takamasa Hirai, Rajkumar Modak, Satoru Kobayashi, Ken-ichi Uchida, Anomalous Ettingshausen effect in iron-carbon alloys, Applied Physics Letters 121, 062401 (2022). arXiv:2206.07322

24) Takumi Yamazaki, Takeshi Seki, Rajkumar Modak, Keita Nakagawara, Takamasa Hirai, Keita Ito,Ken-ichi Uchida,and Koki Takanashi, Thickness dependence of anomalous Hall and Nernst effects in Ni-Fe thin films, Physical Review B 105, 214416 (2022).

23) Hiroto Masuda ,Takeshi Seki ,Yuta Yamane ,Rajkumar Modak ,Ken-ichi Uchida ,Jun’ichi Ieda ,Yong-Chang Lau ,Shunsuke Fukami ,and Koki Takanashi, Large Antisymmetric Interlayer Exchange Coupling Enabling Perpendicular Magnetization Switching by an In-Plane Magnetic Field, Physical Review Applied 17, 054036 (2022).

22) H. Mizuno, R. Modak, T. Hirai, A. Takahagi, Y. Sakuraba,R. Iguchi, and K. Uchida, Deposition temperature dependence of thermo-spin and magneto-thermoelectric conversion in Co2MnGa films on Y3Fe5O12 and Gd3Ga5O12, Applied Physics Letters 120, 202401 (2022). arXiv:2203.10566

21) Rajkumar Modak, Masayuki Murata, Dazhi Hou, Asuka Miura, Ryo Iguchi, Bin Xu, Rulei Guo, Junichiro Shiomi, Yuya Sakuraba, Ken-ichi Uchida,"Phase-transition-induced giant Thomson effect for thermoelectric cooling", Applied Physics Reviews 9, 011414 (2022). Featured. Also  featured as a "AIP Scilights" : Thomson effect transforms FeRh-based alloys into thermoelectric materials. (arXiv:2111.02707).

20) Hiroto Masuda, Rajkumar Modak, Takeshi Seki, Ken-ichi Uchida, Yong-Chang Lau, Junsaku Nitta, and Koki Takanashi,"Spin Hall effect in a non-equilibrium Cu76Ir24 alloy measured at various temperatures", AIP Advances 11, 095221 (2021).

19) Rajkumar Modak, A. Srinivasan, V. V. srinivasu, “Understanding low field microwave absorption in Ni-Mn based Heusler alloy films”, Materials Research Bulletin 143, 111453 (2021) 

18) T. Hirai, R. Modak, A. Miura, T. Seki , K. Takanashi, and K. Uchida, “Temperature dependence of anisotropic magneto-Seebeck effect in NiPt alloys”, Applied Physics Express 14, 073001 (2021)

17) Jian Wang, Asuka Miura, Rajkumar Modak, Yukiko K. Takahashi, and Ken-ichi Uchida, "Magneto-optical design of anomalous Nernst thermopile", Scientific Reports 11, 11228 (2021).

16) Rajkumar Modak, Kazuki Goto, Shigenori Ueda, Yoshio Miura, Ken-ichi Uchida, Yuya Sakuraba, "Combinatorial tuning of electronic structure and thermoelectric properties in Co2MnAl1-xSix Weyl semimetals", APL Materials  9, 031105 (2021) (arXiv:2102.06412)

15) Hiroto Masuda†, Rajkumar Modak†, Takeshi Seki, Ken-ichi Uchida, Yong Chang Lau, Yuya Sakuraba, Ryo Iguchi, Koki Takanashi, "Large spin-Hall effect in non-equilibrium binary copper alloys beyond the solubility limit", Communications Materials 1, 75 (2020). † equal contribution

14) Rajkumar Modak, Ryo Iguchi, Hossein Sepehri-Amin, Asuka Miura, and and Ken-ichi Uchida, "Simultaneous direct measurements of conventional and inverse magnetocaloric effects in Ni-Mn-based Heusler alloys using lock-in thermography technique", AIP Advances 10, 065005 (2020).

13) Rajkumar Modak and Ken-ichi Uchida, "Enhancement of temperature change induced by anomalous Ettingshausen effect in thin Ni films on suspended membrane substrates", Applied Physics Letters 116, 032403 (2020).

12) A. Gayen, Rajkumar Modak, A. Srinivasan, V.V. Srinivasau, A. Perumal, "Thickness dependent magneto-static and magneto-dynamic properties of CoFeB thin films", Journal of Vacuum Science and Technology A 37, 031513 (2019).

11) Rajkumar Modak and A Srinivasan, "Enhanced room temperature magneto-caloric effect upon Fe/Co substitution in Ni-Mn-In films", Journal of Applied Physics 125, 085302 (2019).

10) Rajkumar Modak, M. Manivel Raja and A Srinivasan, "Enhanced magneto-caloric effect upon fourth element (Cu, Fe, Co) substitution in Ni-Mn-Sn thin films", Applied Physics A 125, 57 (2019).

9) Rajkumar Modak and A Srinivasan, "Enhanced Magneto-static and Magneto-dynamic Properties in Fe/Co Substituted Ni-Mn-In Alloy Films", IEEE Transactions on Magnetics 54, 6100405 (2018).

8) A. Srinivasan, R. Modak, C. Swapna and V. V. Srinivasu, "New aspects of microwave absorption in ferromagnetic Ni-Mn-Sn thin films", Acta Physica Polonica A 134, 178 (2018).

7) Rajkumar Modak, V. V. Srinivasu and A. Srinivasan, "Effect of Cu/Fe/Co substitution on static and dynamic magnetic properties of Ni-Mn-Sn alloy thin films", Journal of Magnetism and Magnetic Materials 464, 50 (2018).

6) Rajkumar Modak, M. Manivel Raja, V.V. Srinivasu and A. Srinivasan, "Structural, magneto-static and magneto-dynamic properties of Fe substituted Ni-Mn-In films", Thin Solid Films 653, 384 (2018).

5) Rajkumar Modak, M. Manivel Raja and A. Srinivasan,"Enhanced magneto-caloric effect upon Co substitution in Ni-Mn-Sn thin films", Journal of Magnetism and Magnetic Materials 448, 146 (2018).

4) Rajkumar Modak, B. Samantaray, P. Mandal and A. Srinivasan, " Thickness dependent structural, magnetic and magneto-dynamic properties of Mn rich Ni-Mn-Sn films ", Journal of Alloys and Compounds 692, 529 (2017).

3) Bhargab Deka, Rajkumar Modak, Pralay Paul and Ananthakrishnan Srinivasan, "Effect of atomic disorder on magnetization and half-metallic character of Cr2CoGa alloy", Journal of Magnetism and Magnetic Materials 418, 107 (2016).

2) Rajkumar Modak, B. Samantaray, P. Mandal and A. Srinivasan, "Low Gilbert damping and in-plane magnetic anisotropy in Ni-Mn-Sn thin film with high L21 order ", Applied Physics A 122, 252 (2016).

1) Rajkumar Modak,  B. Deka, M. Manivel Raja and A. Srinivasan, "Significant room temperature magneto-caloric effect in Ni-Mn-Sn thin films", Advanced Science Letters 22, 26 (2016).

Conference proceedings

4) H. Masuda, Y. Yamane, T. Seki, K. Raab, T. Dohi, R. Modak, K. Uchida, J. Ieda, M. Kläui, and K. Takanashi, Current-induced magnetization switching in magnetic multilayers with interlayer exchange coupling by dual spin-orbit torque, 2023 IEEE International Magnetic Conference - Short Papers (INTERMAG Short Papers).

3) Arnab Kumar Das, Rajkumar Modak and A. Srinivasan, "Structural and optical properties of electrospun MoO3 nanowires", AIP Conference Proceedings 1953, 030021(2018).

2) Rajkumar Modak, B. Samantaray, P. Mandal, V. V. Srinivasu and A. Srinivasan, "Comparison of field swept ferromagnetic resonance methods – A case study using Ni-Mn-Sn films", AIP Conference Proceedings 1953, 120006 (2018).

1) R. Modak,  B. Deka, A.K. Singh, A. Gayen, A. Perumal, M. Manivel Raja and A. Srinivasan, "Structural and magnetic properties of Ni-Mn-Sn thin films", AIP Conference Proceedings 1665, 080072 (2015).

Work presented in Conferences/Workshops/Seminars

22)Rajkumar Modak, Takamasa Hirai, Yuya Sakuraba, Seiji Mitani, Koichi Oyanagi, Takeshi Seki, and Ken-ichi Uchida, High-throughput investigation of magnetoresistance materials based on lock-in thermography. ICMAMGA 2023, Hyderabad, India, Dec 04-06, 2023.

21) R. Modak, T. Hirai, Y. Sakuraba, S. Mitani, K. Oyanagi, T. Seki and K. Uchida. High-throughput screening of magnetoresistance materials based on lock-in thermography. Spin caloritronics XII, Tsukuba, Japan, May 22 - 25, 2023.

20) Rajkumar Modak , Weinan Zhou,Yuya Sakuraba, and Ken-ichi Uchida. Effect of layer thickness to the in-plane coercive field and anomalous Nernst effect in Sm/Co multilayer films. Intermag 2023, Sendai, Japan, May 15 - 19, 2023.

19) MODAK Rajkumar, Masayuki Murata, Dazhi Hou, Asuka Miura, IGUCHI, Ryo, Bin Xu, Rulei Guo, Junichiro Shiomi, SAKURABA, Yuya, UCHIDA, Kenichi. Magnetic phase-transition-induced giant Thomson effect for thermoelectric cooling. The 83rd JSAP Autumn meeting 2022, Kawauchi, Sendai, Japan, September 20 - 23, 2022.

18) R. Modak, Y. Sakuraba, T. Hirai, T. Yagi, H. Sepehri Amin, W. Zhou, H. Masuda, T. Seki, K. Takanashi, T. Ohkubo, and K. Uchida, Sm-Co-based amorphous alloy films for zero-field transverse thermoelectric generation, The 24th International Colloquium on Magnetic Films and Surfaces, Okinawa, Japan, July 10 - 15, 2022.

17) R. Modak, Y. Sakuraba, T. Hirai, T. Yagi, H. Sepehri Amin, H. Masuda, T. Seki, K. Takanashi, W. Zhou, T. Ohkubo, and K. Uchida, Sm-Co-based amorphous alloy films for zero-field transverse thermoelectric generation, The 69th JSAP spring meeting 2022, Sagamihara, Tokyo,  Japan, March 22 - 26, 2022.

16) R. Modak, Y. Sakuraba, T. Hirai, T. Yagi, H. Sepehri Amin, H. Masuda, T. Seki, K. Takanashi, W. Zhou, T. Ohkubo, and K. Uchida, Combinatorial investigation of Sm-Co-based amorphous alloy films for zero-field transverse thermoelectric generation, The Symposium of Magnetism and Spintronics, Bhubaneswar, Odish, India, November 25 - 27, 2021.

15) Efficient Tuning of Electronic, Transport, and Thermoelectric Properties of Weyl Semimetal Co2MnAl1-xSix Composition-Spread Thin Film, MODAK Rajkumar, MIURA Yoshio, UEDA Shigenori, UCHIDA Kenichi, SAKURABA Yuya, Presented at "INTERMAG2021", Lyon, France, April 26-30, 2021. Link

14)Efficient Tuning of Electronic, Transport, and Thermoelectric Properties of Weyl Semimetal Co2MnAl1-xSix Composition-Spread Thin Film, R. Modak, Y. Miura, S. Ueda, K. Uchida, and Y. Sakuraba,"The 68th JSAP Spring Meeting", Tokyo, Japan, March 16-19, 2021. 

13) Enhancement of temperature change induced by anomalous Ettingshausen effect in ferromagnetic metal films on suspended membrane substrates, MODAK Rajkumar , UCHIDA Kenichi, Presented at "The 67th JSAP Spring Meeting" , 12-15 Mar. 2020, Yotsuya Campus, Sophia University, Tokyo, Japan.

12) Low field microwave absorption and its correlation with magnetization in Ni-Mn-Sn based Heusler alloy films, Bala Ismail Adamu, Rajkumar Modak, A. Srinivasan, V. V. Srinivasu, Presented at "International Conference on Magnetic Materials and Applications" (ICMAGMA-2018), 09-13 Dec. 2018, Bhubaneswar, India.

11) Evaluation of Ni-Mn-X-Sb (X=Si/Fe) alloys for magnetic refrigeration application, Rajkumar Modak, Arnab Das and A. Srinivasan, Presented at IIT Guwahati "Research Conclave 2018" (RC-2018) , 8-11 Mar. 2018, Guwahati, India.

10) Comparison of field swept ferromagnetic resonance methods – A case study using Ni-Mn-Sn films, Rajkumar Modak, B. Samantaray, P. Mandal, V. V. Srinivasu and A. Srinivasan, Presented at "2nd International Conference on Condensed Matter & Applied Physics" (ICC-2017), 24-25 Nov. 2017, Bikaner, India.

9) Structural and optical properties of electrospun MoO3 nanowires, Arnab Kumar Das, Rajkumar Modak and A. Srinivasan, Presented at "2nd International Conference on Condensed Matter & Applied Physics" (ICC-2017), 24-25 Nov. 2017, Bikaner, India.

8) Annealing temperature dependent structural transition and associated magnetic properties of Fe substituted thin films of Ni-Mn-In alloy, Rajkumar Modak, M. Manivel Raja, V.V. Srinivasu and A. Srinivasan, Presented at "Condensed Matter Days- 2017" (CMDAYS-2017) , 29 - 31 Aug. 2017, Tezpur, India.

7) Comparison of field swept ferromagnetic resonance methods for investigating magnetic thin films, Rajkumar Modak and Ananthakrishnan Srinivasan, Presented at "International Conference on Sophisticated Instruments in Modern Research" (ICSIMR-2017) , 30 Jun. -1 Jul. 2017, Guwahati, India.

6) Very Low effective magnetic anisotropy and low Gilbert damping in Fe substituted Ni-Mn-In films, Rajkumar Modak, M. Manivel Raja, V.V. Srinivasu and A. Srinivasan, Presented at IIT Guwahati "Research Conclave 2017" (RC-2017) , 16-19 Mar. 2017, Guwahati, India.

5) Enhanced magneto-caloric effect upon Co substitution in Ni-Mn-Sn thin films, Rajkumar Modak, M. Manivel Raja and A. Srinivasan, Presented at "International Conference on Magnetic Materials and Applications" (ICMAGMA-2017) , 01-03 Feb. 2017, Hyderabad, India.

4) Structural and morphological studies of Mg doped ZnO nanowires prepared by electrospinning route, Arnab Kumar Das, Rajkumar Modak and A. Srinivasan, Presented at "International Conference on Nanoscience, Nanotechnology & Advanced Materials" (NANOS-2015) , 14-17 Dec. 2015, Visakhapatnam, India.

3) Effect of Sputtering Gas Pressure on the Structural and Magnetic Properties of Ni-Mn-Sn Thin Films, Rajkumar Modak and Ananthakrishan Srinivasan, Presented at "International Conference on Nanoscience, Nanotechnology & Advanced Materials" (NANOS-2015) , 14-17 Dec. 2015, Visakhapatnam, India.

2) Structural and magnetic properties of  Ni-Mn-Sn thin films, R. Modak,  B. Deka, A.K. Singh, A. Gayen, A. Perumal, M. Manivel Raja and A. Srinivasan, Presented at "59th DAE Solid State Physics Symposium" (DAE-SSPS-2014), 16-20 Dec. 2014, Vellore, India.

1) Significant room temperature magneto-caloric effect in Ni-Mn-Sn thin films, R. Modak, B. Deka, M. Manivel Raja and A. Srinivasan, Presented at The First International Conference on "Emerging Materials: characterization & Application" (EMCA-2014) , 04-06 Dec. 2014, Kolkata, India.

Employment

2023.9 - present : Special Researcher, at National Institute for Materials Science, Tsukuba, Japan

2021.9 - 2023.8 : Japan Society for the Promotion of Science (JSPS) Research Fellow, at National Institute for Materials Science, Tsukuba, Japan

2019.4 - 2021.8 : Postdoctoral Researcher, at National Institute for Materials Science, Tsukuba, Japan

Academic Experience

2017.7 - 2017.11 - Teaching Assistant at PH311:Electronics LabII (B.Tech. 3rd year students), at Dept. of Physics, IIT Guwahati.

2017.1 - 2017.5 - Teaching Assistant at PH210: Analog Electronics (B.Tech. 2nd year students), at Dept. of Physics, IIT Guwahati.

2016.7 - 2016.11 - Teaching Assistant at PH311:Electronics LabII (B.Tech. 3rd year students), at Dept. of Physics, IIT Guwahati.

2014.7 - 2014.11 - Teaching Assistant at PH311: Electronics LabII (B.Tech. 3rd year students), at Dept. of Physics, IIT Guwahati.

2014.1 - 2015.5 - Teaching Assistant at PH110: Physics Laboratory (B.Tech. 1st year students), at Dept. of Physics, IIT Guwahati.

Education

Doctor of Philosophy (Ph.D. in Physics), Dept. of Physics, IIT Guwahati , Guwahati, Assam, India (2019.1).

Master of Science in Physics (M.Sc. Physics), Dept. of Physics, IIT Delhi, Hauz Khas, New Delhi, India (2013.6).

Bachelor of Science in Physics (B.Sc. Physics), Krishnanagar Govt. College,University of Kalyani, Nadia, W.B., India (2011.6).

Award and Grant

2021 - 2023: JSPS Postdoctoral Fellowship for Overseas Researchers (Standard), Japan

2013 - 2018 : Institute fellow (for Research) at IIT Guwahati, India

2008 - 2013 : Inspire Scholar under Scholarship for Higher Education (SHE), Department of Science and Technology (DST), Government of India

2021 - 2023: Grant-in-Aid for JSPS Fellows, Creation of spin-caloritronic Heusler alloys and their hybrid structures, JSPS Kakenhi Project, ¥2,300,000 (Direct Cost)

Academic Society Membership

Member of Japan Society of Applied Physics (2020-)

Student Member of Materials Research Society (2015-2016)

Other Activities

  1) Volunteered at International Conference on Magnetic Materials and Applications (MAGMA-2013), held on 5-7th Dec. 2013 at Dept. of Physics, IIT Guwahati.

  2) Volunteered to represent Dept. of Physics, IIT Guwahati in National Science Day, held on 28th Feb.-01st Mar. 2015 at IASST, Guwahati 

 3) Conducted an "Intra IIT workshop on XRD Basics" as a Trainer organized by Research Scholar Forum, held on 27-28th Jan. 2017 at Dept. of Physics, IIT Guwahati.

 4) Volunteered at International Conference on Sophisticated Instruments in Modern Research (ICSIMR-2017), held on 30th Jun. -1st Jul. 2017 at CIF, IIT Guwahati.