DEVARAJAN U

@mtrdc.lan

Research Associate, Microwave Tube Research and Development Centre, Bengaluru
MTRDC-DRDO, BENGALURU

DEVARAJAN U


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https://researchid.co/devarajan

RESEARCH INTERESTS

Materials science, High pressure and low temperature physics, Solid state Physics and magnetism, Superconductivity, Crystal Growth, thin films and Multi ferroics.
14

Scopus Publications

310

Scholar Citations

10

Scholar h-index

10

Scholar i10-index

Scopus Publications

  • Investigation of Magnetic and Transport Properties of Co2FeSi Spin Glass Heusler Alloy Under Extreme Conditions
    U. Devarajan, P. Sivaprakash, Alga B. Garg, Ikhyun Kim, S. Arumugam
    Journal of Superconductivity and Novel Magnetism, 2023
  • Transformation of magnetic ordering in MnCo1-xNixGe (x = 0–0.6) alloys, its investigations on structural, transport, magnetic, and magnetocaloric properties
    U. Devarajan, Sunil Nair, C. Venkateswaran
    Materials Today Proceedings, 2022
  • Induced triplet transitions by the effect of antiferromagnetic (Sm) substitution and investigations on structural, magnetic, magnetocaloric properties of Mn1-xSmxCoGe heulser alloys
    U. Devarajan, P. Sivaprakash, C. Venkateswaran, P. Hariharan, Y. Kawamura, C. Sekine, S. Arumugam
    Journal of Magnetism and Magnetic Materials, 2021
  • Lithium-antimony co-doping induced morphology transition in spray deposited SnO2 thin films
    D. Paul Joseph, U. Devarajan, Jean Maria Fernandes, R. Ramarajan, M. Kovendhan, Nandarapu Purushothamreddy, Reddivari Muniramaiah, C. Venkateswaran
    Surfaces and Interfaces, 2021
  • Investigations on Cu induced couple-decoupled magneto-structural transition in MnCoGe alloys
    U Devarajan, Sunil Nair
    Materials Research Express, 2019
  • Structural, transport, magnetic, magnetocaloric properties and critical analysis of Ni-Co-Mn-Ga Heusler alloys
    S. Arumugam, U. Devarajan, S. Esakki Muthu, Sanjay Singh, R. Thiyagarajan, M. Manivel Raja, N.V. Rama Rao, Alok Banerjee
    Journal of Magnetism and Magnetic Materials, 2017
    In this work, we have investigated structural, transport, magnetic, magnetocaloric (MC) properties and critical exponents analysis of the (Ni 2.1− x Co x )Mn 0.9 Ga ( x = 0, 0.04, 0.12 and 0.2) Heusler alloys. For all compositions, cubic austenite (A) phase with metallic character is observed at room temperature (RT). With increasing of Co content, magnitude of resistivity decreases, whereas residual resistivity ( ρ 0 ) and electron scattering factor ( A ) increases linearly. Magnetic measurements exhibit that ferromagnetic (FM) Curie temperature ( T C A ) increases towards RT by increasing Co concentration. All samples show conventional MC and maximum magnetic entropy change (Δ S M peak ) of −2.8 Jkg −1 K −1 is observed for x = 0.12 at 147 K under 5 T. Further, hysteresis is observed between cooling and warming cycles around FM-PM ( T C A ) transition in x = 0, 0.04 samples, which suggests that first order nature of transition. However, there is no hysteresis across T C A for x = 0.12 and 0.2 samples suggesting second-order nature of the transition. The critical exponents are calculated for x = 0.12 sample around T C A using Arrott plot and Kouvel-Fisher method, the estimated critical exponents are found closer to the mean-field model reveals the long range ferromagnetic ordering in this composition.
  • Effect of hydrostatic pressure on the magnetic, exchange bias and magnetocaloric properties of Ni45.5Co2Mn37.5Sn15
    S. Arumugam, Subrata Ghosh, Arup Ghosh, U. Devarajan, M. Kannan, L. Govindaraj, Kalyan Mandal
    Journal of Alloys and Compounds, 2017
    In this study, we report the effect of hydrostatic pressure (P) and magnetic field (H) on the magnetization, magnetocaloric effect and exchange bias in a Ni45.5Co2Mn37.5Sn15 Heusler alloy. At ambient pressure, the martensitic transition temperature (TM) shifts to lower temperatures with a rate of dTM/dμ0H ∼ 3.29 K/T. On the other hand, TM increases rapidly to higher temperatures with dTM/dP ∼31.90 K/GPa when hydrostatic pressure is applied. The peak value of magnetic entropy change due to change in magnetic field of 5 T is found to decrease with increasing pressure. Although, the relative cooling power (RCP) increases from ∼189 Jkg-1 to ∼ 204 Jkg-1 during cooling cycle, a significant drop in net RCP is obtained from the measurements under heating cycle. The coercivity of the sample at a given temperature merely changes, but the exchange bias effect is improved by applying pressure.
  • Coupled magnetostructural transition in Ni-Mn-V-Ga Heusler alloys and its effect on the magnetocaloric and transport properties
    U Devarajan, M Kannan, R Thiyagarajan, M Manivel Raja, N V Rama Rao, Sanjay Singh, D Venkateshwarlu, V Ganesan, M Ohashi, S Arumugam
    Journal of Physics D Applied Physics, 2015
    In the present work, the magnetocaloric and transport properties of Ni2.2Mn0.72-xVxGa1.08 (x = 0.0, 0.04, 0.08, 0.12) magnetic shape memory alloys are investigated. The alloys show a coupled magnetostructural transition from paramagnetic austenite to ferromagnetic martensite in a composition range of 0 <= x <= 0.08. For higher V substitution (x = 0.12), the martensite transition is lower than the conventional ferromagnetic transition. Large magnetic entropy change values of about 12.4, 16.2 and 19 J kg(-1) K-1 and corresponding refrigeration capacities of 60.6, 82.5, and 103 J kg(-1) were observed for x = 0, 0.04 and 0.08 alloys, respectively. The above two parameters linearly increase with increasing magnetic field. The indirect adiabatic temperature change calculated from the heat capacity measurement is found to be at its maximum for x = 0.12 at H = 8 T. The magnetoresistance is observed to increase from 0 % (x = 0.12) to 28 % (x = 0) at the maximum field of 8 T. The Sommerfeld coefficients are almost the same for the parent and a V-doped sample, which reveals a low free electron density, and the Debye coefficients decrease with an increase in V doping, confirming the phenomenon of electron-phonon scattering. The critical exponents at second order magnetic transition for x = 0.12 are calculated as beta = 0.482, gamma = 1.056, delta = 3.021, which agrees closely with mean field theory.
  • Investigations on the electronic transport and piezoresistivity properties of Ni2-XMn1+XGa (X = 0 and 0.15) Heusler alloys under hydrostatic pressure
    U. Devarajan, Sanjay Singh, S. Esakki Muthu, G. Kalai Selvan, P. Sivaprakash, S. Roy Barman, S. Arumugam
    Applied Physics Letters, 2014
    The resisitivity of Ni2−XMn1+XGa (X = 0 and 0.15) magnetic shape memory alloys has been investigated as a function of temperature (4–300 K) and hydrostatic pressure up to 30 kilobars. The resistivity is suppressed (X = 0) and enhanced (X = 0.15) with increasing pressure. A change in piezoresistivity with respect to pressure and temperature is observed. The negative and positive piezoresistivity increases with pressure for both the alloys. The residual resistivity and electron-electron scattering factor as a function of pressure reveal that for Ni2MnGa the electron-electron scattering is predominant, while the X = 0.15 specimen is dominated by the electron-magnon scattering. The value of electron-electron scattering factor is positive for both the samples, and it is decreasing (negative trend) for Ni2MnGa and increasing (positive trend) for X = 0.15 with pressure. The martensite transition temperature is found to be increased with the application of external pressure for both samples.
  • Influence of chemical substitution, magnetic field, and hydrostatic pressure effect on martensitic and intermartensitic transition in bulk Ni 49-xCuxMn38Sn13 (0.5 ≤ x ≤ 2) Heusler alloys
    S. Esakki Muthu, N. V. Rama Rao, R. Thiyagarajan, U. Devarajan, M. Manivel Raja, S. Arumugam
    Applied Physics Letters, 2014
    In this work, we report the influence of chemical substitution of Ni site by Cu, magnetic field of 50 kOe, and external pressure effect on martensite and intermartensite transformations in Ni49-xCuxMn38Sn13 (0.5 ≤ x ≤ 2) Heusler alloys. The substitution of Cu for Ni decreases the lattice parameter and introduces the intermartensitic transformation in this alloy series. Further, the intermartensitic transformation vanishes for higher Cu content (x = 2). The application of external magnetic field and hydrostatic pressure suppresses the intermartensitic transformation in Ni49-xCuxMn38Sn13 (0.5 ≤ x ≤ 1.5) and Ni49-xCuxMn38Sn13 (x = 0.5) alloys, respectively. Also, the external magnetic field favors the stabilization of austenite phase while the external hydrostatic pressure favors the martensite phase.
  • Investigation of the influence of hydrostatic pressure on the magnetic and magnetocaloric properties of Ni2-XMn1+XGa (X = 0, 0.15) Heusler alloys
    U. Devarajan, S. Esakki Muthu, S. Arumugam, Sanjay Singh, S. R. Barman
    Journal of Applied Physics, 2013
  • Synthesis, structural, electrical and magnetic studies of La 0.5Ca 0.45-xSr xBa 0.05MnO 3
    B. Munirathinam, M. Krishnaiah, U. Devarajan, S. Esakki Muthu, S. Arumugam
    Journal of Physics and Chemistry of Solids, 2012
  • Effect of magnetic field and pressure on charge-orbital ordering in Pr(Sr1-xCax)2Mn2O 7 (x=0.4 and 0.9) single crystals
    R. Thiyagarajan, Guochu Deng, S. Arumugam, D. Mohan Radheep, U. Devarajan, A. Murugeswari, P. Mandal, Ekaterina Pomjakushina, Kazimierz Conder
    Journal of Applied Physics, 2011
  • Effect of Ni/Mn concentration on exchange bias properties in bulk Ni 50-xMn37xSn13 Heusler alloys
    S. Esakki Muthu, N. V. Rama Rao, D. V. Sridhara Rao, M. Manivel Raja, U. Devarajan, S. Arumugam
    Journal of Applied Physics, 2011

RECENT SCHOLAR PUBLICATIONS

  • Synthesis and Characterization of Scandia doped Tungsten Nano Powder
    PSSKD U. Devarajan, K. Santhosh Kumar, V. Deepa, M. Vijay Kumar
    National Conference on Emerging Trends Vacuum Electron Devices and … , 2024
    2024
  • Investigation of Magnetic and Transport Properties of Co2FeSi Spin Glass Heusler Alloy Under Extreme Conditions
    SA U. Devarajan, P. Sivaprakash, Alga B. Garg, Ikhyun Kim
    Journal of Superconductivity and Novel Magnetism 36 (103), 1611–1618 , 2023
    2023
    Citations: 3
  • Tunable Multifunctionality in Heusler alloys
    SA U. Devarajan
    Recent Advances in Perovskite Materials, 1-17 , 2022
    2022
  • Transformation of magnetic ordering in MnCo1-xNixGe (x = 0–0.6) alloys, its investigations on structural, transport, magnetic, and magnetocaloric properties
    SNCV U. Devarajan
    Materials Today Proceedings 65 (1), 168-175 , 2022
    2022
    Citations: 2
  • Induced triplet transitions by the effect of antiferromagnetic (Sm) substitution and investigations on structural, magnetic, magnetocaloric properties of Mn1-Sm CoGe Heulser alloys
    SA U. Devarajan, P. Sivaprakash, C. Venkateswaran, P. Hariharan, Y. Kawamura ...
    Journal of Magnetism and magnetic materials 529, 167912 , 2021
    2021
    Citations: 12
  • Effect of annealing on Structural, Morphological and Vibrational properties in Spinel Oxides [Fe1-x XxCr2O4 (X=Cu, Ni, Co)]
    SSCV U. Devarajan
    University of Madras, Chennai , 2021
    2021
  • Analysis of structural, magnetic, electrical properties of Mn1-xNixCoGe alloys
    SNCV U. Devarajan
    Intermetallics , 2021
    2021
  • Enhancement of Curie transition by Substituting Sb in MnCo1-xSbxGe (x=0, 0.2, 0.4, 0.6) alloys and its structural, morphogical, magnetic, magnetocalric investigations
    SMCV U. Devarajan
    2021
  • Lithium-antimony co-doping induced morphology transition in spray deposited SnO2 thin films
    CV D. PaulJoseph, U. Devarajan, Jean Maria Fernandes, R. Ramarajan, M ...
    Surface and Interfaces 23, 100918 , 2021
    2021
    Citations: 23
  • Investigations on Cu induced couple-decoupled magneto-structural transition in MnCoGe alloys
    UDS Nair
    Materials Research Express 6, 106117 , 2019
    2019
    Citations: 8
  • Study on magnetocaloric and critical analysis of Ni doped MnCoGe
    U Devarajan, S Nair
    Proceedings of the national conference on quantum condensed matter, 1-1 , 2018
    2018
  • Effect of hydrostatic pressure on the magnetic, exchange bias and magnetocaloric properties of Ni45.5Co2Mn37.5Sn15
    KM S. Arumugam, Subrata Ghosh, Arup Ghoshb, U. Devarajan, M. Kannan, L ...
    Journal of Alloys and Compounds 712, 714-719 , 2017
    2017
    Citations: 31
  • Structural, transport, magnetic, magnetocaloric properties and critical analysis of Ni-Co-Mn-Ga Heusler alloys
    AB S. Arumugam , U. Devarajan, S. Esakki Muthu , Sanjay Singh , R ...
    Journal of Magnetism and Magnetic Materials 442, 460-467 , 2017
    2017
    Citations: 17
  • Effect of hydrostatic pressure on the magnetic, exchange bias and magnetocaloric properties of Ni45. 5Co2Mn37. 5Sn15
    A GHOSH, S Ghosh, K Mandal, S Arumugam, U DEVARAJAN, M Kannan, ...
    Elsevier BV , 2017
    2017
  • Investigation on structural, transport magnetic and thermal properties of Heusler alloys under extreme conditions.
    UD Arumugam
    Bharathidasan University, Tiruchirappalli , 2016
    2016
  • Spin polarization behavior of Co2FeSi Heusler alloy by magnetic and transport studies
    SA U. Devarajan
    2016
  • Coupled magnetostructural transition in Ni-Mn-V-Ga Heusler alloys and its effect on the magnetocaloric and transport properties
    MOSA U. Devarajan, M. Kannan, R. Thiyagarajan, M. Manivel Raja, N. V. Rama ...
    J. Phys. D: Appl. Phys. 49, 065001 , 2015
    2015
    Citations: 17
  • Investigations on the electronic transport and piezoresistivity properties of Ni {sub 2− X} Mn {sub 1+ X} Ga (X= 0 and 0.15) Heusler alloys under hydrostatic pressure
    U Devarajan, G Kalai Selvan, P Sivaprakash, S Singh, S Esakki Muthu, ...
    Applied Physics Letters 105 (25) , 2014
    2014
  • Investigations on the electronic transport and piezoresistivity properties of Ni2−XMn1+XGa (X=0 and 0.15) Heusler alloys under hydrostatic pressure
    SRBSA U. Devarajan, Sanjay Singh, S. Esakki Muthu, G. Kalai Selvan, P ...
    Applied Physics Letters 105 (25), 252401 , 2014
    2014
    Citations: 26
  • “Influence of chemical substitution, magnetic field, and hydrostatic pressure effect on martensitic and intermartensitic transition in bulk Ni49-xCuxMn38Sn13 (0.5≤ x ≤ 2 …
    S. Esakki Muthu, N. V. Rama Rao, R. Thiyagarajan, U. Devarajan, M. Manivel ...
    Applied. Physics. Letter 104, 092404 , 2014
    2014
    Citations: 34

MOST CITED SCHOLAR PUBLICATIONS

  • “Effect of Ni/Mn concentration on exchange bias properties in bulk Ni50-xMn37+xSn13 Heusler alloys”,
    S. Esakki Muthu, N. V. Rama Rao, D. V. Sridhara Rao, M. Manivel Raja, U ...
    Journal of Applied Physics 110, 023904 , 2011
    2011
    Citations: 63
  • Synthesis, structural, electrical and Magnetic studies of La0.5Ca0.45-xSrxBa0.05MnO3
    B.Munirathinam, M.Krishnaiah, U.Devarajan, S.Esakki Muthu, S.Arumugam
    Journal of Physics and Chemistry of Solids 73, 925-930 , 2012
    2012
    Citations: 37
  • “Influence of chemical substitution, magnetic field, and hydrostatic pressure effect on martensitic and intermartensitic transition in bulk Ni49-xCuxMn38Sn13 (0.5≤ x ≤ 2 …
    S. Esakki Muthu, N. V. Rama Rao, R. Thiyagarajan, U. Devarajan, M. Manivel ...
    Applied. Physics. Letter 104, 092404 , 2014
    2014
    Citations: 34
  • Effect of hydrostatic pressure on the magnetic, exchange bias and magnetocaloric properties of Ni45.5Co2Mn37.5Sn15
    KM S. Arumugam, Subrata Ghosh, Arup Ghoshb, U. Devarajan, M. Kannan, L ...
    Journal of Alloys and Compounds 712, 714-719 , 2017
    2017
    Citations: 31
  • “Investigation of the influence of hydrostatic pressure on the magnetic and magnetocaloric properties of Ni2-XMn1+XGa (X= 0, 0.15) Heusler alloys”,
    SRB U. Devarajan, S. Esakki Muthu, S. Arumugam, Sanjay Singh
    Journal of Applied Physics 114, 053906 , 2013
    2013
    Citations: 30
  • Investigations on the electronic transport and piezoresistivity properties of Ni2−XMn1+XGa (X=0 and 0.15) Heusler alloys under hydrostatic pressure
    SRBSA U. Devarajan, Sanjay Singh, S. Esakki Muthu, G. Kalai Selvan, P ...
    Applied Physics Letters 105 (25), 252401 , 2014
    2014
    Citations: 26
  • Lithium-antimony co-doping induced morphology transition in spray deposited SnO2 thin films
    CV D. PaulJoseph, U. Devarajan, Jean Maria Fernandes, R. Ramarajan, M ...
    Surface and Interfaces 23, 100918 , 2021
    2021
    Citations: 23
  • Structural, transport, magnetic, magnetocaloric properties and critical analysis of Ni-Co-Mn-Ga Heusler alloys
    AB S. Arumugam , U. Devarajan, S. Esakki Muthu , Sanjay Singh , R ...
    Journal of Magnetism and Magnetic Materials 442, 460-467 , 2017
    2017
    Citations: 17
  • Coupled magnetostructural transition in Ni-Mn-V-Ga Heusler alloys and its effect on the magnetocaloric and transport properties
    MOSA U. Devarajan, M. Kannan, R. Thiyagarajan, M. Manivel Raja, N. V. Rama ...
    J. Phys. D: Appl. Phys. 49, 065001 , 2015
    2015
    Citations: 17
  • Induced triplet transitions by the effect of antiferromagnetic (Sm) substitution and investigations on structural, magnetic, magnetocaloric properties of Mn1-Sm CoGe Heulser alloys
    SA U. Devarajan, P. Sivaprakash, C. Venkateswaran, P. Hariharan, Y. Kawamura ...
    Journal of Magnetism and magnetic materials 529, 167912 , 2021
    2021
    Citations: 12
  • Investigations on Cu induced couple-decoupled magneto-structural transition in MnCoGe alloys
    UDS Nair
    Materials Research Express 6, 106117 , 2019
    2019
    Citations: 8
  • “Effect of magnetic field and pressure on charge- orbital ordering in Pr(Sr1-xCax)2Mn2O7 (X= 0.4 and 0.9) single crystals”,
    R. Thiyagarajan, Guochu Deng, S. Arumugam, D. Mohan Radheep, U. Devarajan, A ...
    Journal of Applied Physics 110, 093905 , 2011
    2011
    Citations: 7
  • Investigation of Magnetic and Transport Properties of Co2FeSi Spin Glass Heusler Alloy Under Extreme Conditions
    SA U. Devarajan, P. Sivaprakash, Alga B. Garg, Ikhyun Kim
    Journal of Superconductivity and Novel Magnetism 36 (103), 1611–1618 , 2023
    2023
    Citations: 3
  • Transformation of magnetic ordering in MnCo1-xNixGe (x = 0–0.6) alloys, its investigations on structural, transport, magnetic, and magnetocaloric properties
    SNCV U. Devarajan
    Materials Today Proceedings 65 (1), 168-175 , 2022
    2022
    Citations: 2
  • Synthesis and Characterization of Scandia doped Tungsten Nano Powder
    PSSKD U. Devarajan, K. Santhosh Kumar, V. Deepa, M. Vijay Kumar
    National Conference on Emerging Trends Vacuum Electron Devices and … , 2024
    2024
  • Tunable Multifunctionality in Heusler alloys
    SA U. Devarajan
    Recent Advances in Perovskite Materials, 1-17 , 2022
    2022
  • Effect of annealing on Structural, Morphological and Vibrational properties in Spinel Oxides [Fe1-x XxCr2O4 (X=Cu, Ni, Co)]
    SSCV U. Devarajan
    University of Madras, Chennai , 2021
    2021
  • Analysis of structural, magnetic, electrical properties of Mn1-xNixCoGe alloys
    SNCV U. Devarajan
    Intermetallics , 2021
    2021
  • Enhancement of Curie transition by Substituting Sb in MnCo1-xSbxGe (x=0, 0.2, 0.4, 0.6) alloys and its structural, morphogical, magnetic, magnetocalric investigations
    SMCV U. Devarajan
    2021
  • Study on magnetocaloric and critical analysis of Ni doped MnCoGe
    U Devarajan, S Nair
    Proceedings of the national conference on quantum condensed matter, 1-1 , 2018
    2018