2024/06/15 更新

ジャー アロク クマール
Jha Alok Kumar
Jha Alok Kumar
Scopus 論文情報  
総論文数: 0  総Citation: 0  h-index: 9

Citation Countは当該年に発表した論文の被引用数

所属
大学院工学研究院 物質工学研究系
職名
助教
外部リンク

取得学位

  • インド工科デリー校  -  博士(理学)   2012年07月

学内職務経歴

  • 2017年02月 - 現在   九州工業大学   大学院工学研究院   物質工学研究系     助教

論文

  • Evaluation of temperature dependent vortex pinning properties in strongly pinned YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-δ</inf> thin films with Y<inf>2</inf>BaCuO<inf>5</inf> nanoinclusions 査読有り 国際誌

    Jha A.K., Matsumoto K., Horide T., Saini S., Ichinose A., Mele P., Yoshida Y., Awaji S.

    Superconductivity ( Elsevier )   9   2024年03月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    The pinning of quantized magnetic vortices in superconducting YBa2Cu3O7- δ(YBCO or Y123) thin films with Y2BaCuO5 (Y211) nanoinclusions have been investigated over wide temperature range (4.2–77 K). The concentration of Y211 nanoinclusions has been systematically varied inside YBCO thin films prepared by laser ablation technique using surface modified target approach. Large pinning force density values (Fp ∼ 0.5 TNm−3 at 4.2 K, 9 T) have been observed for the YBCO film with moderate concentration of Y211 nanoinclusions (3.6 area % on ablation target). In addition, uniform enhancement in critical current density (Jc) was observed in the angular dependent Jc measurement of YBCO+Y211 nanocomposite films. Y211 nanoinclusions have been found to be very efficient in pinning the quantized vortices thereby enhancing the in-field Jc values over a wide range of temperature. Increasing the concentration of Y211 secondary phase into Y123 film matrix results into agglomeration of Y211 phase and observed as increased Y211 nanoparticle size. These larger secondary phase nanoparticles are not as efficient pinning centers at lower temperatures as they are at higher temperatures due to substantial reduction of the coherence length at lower temperatures. Investigation of the temperature dependence of Jc for YBCO+Y211 nanocomposite films has been conducted and possible vortex pinning mechanism in these nanocomposite films has been discussed.

    DOI: 10.1016/j.supcon.2024.100087

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  • Flux pinning characteristics of YBCO: NaNbO<inf>3</inf> by introducing artificial pinning centers with different morphology 査読有り 国際誌

    Dahiya M., Kumar R., Kumar D., Jha A.K., Khare N.

    Ceramics International ( Elsevier )   2021年01月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)

    Introduction of artificial pinning centres in different morphology is a beneficial way to improve the flux pinning properties of a YBCO compound. In the present study, we report the effect of addition of sodium niobate (NaNbO3) nanostructures in two different form i.e. nanorods (NRs) and nanoparticles (NPs) with a varied wt% (0, 0.5, and 1 wt%) on the pinning capabilities of bulk YBCO polycrystalline samples. The orthorhombic crystal structure of YBCO was confirmed by the XRD spectra even in the nanocomposite samples. The existence of NPs or NRs on the surface and between the superconducting grains of YBCO was confirmed by morphological analysis. The critical temperature (Tc) remains almost unchanged as compared to pure YBCO on addition of NaNbO3 nanostructure in YBCO compound upto 1 wt% concentration. Even at higher fields (upto 6 T) and higher temperatures (upto 75 K), the addition of NaNbO3 NPs or NRs in YBCO nanocomposite resulted in a significant increase of ~2.6 times in the critical current density as compared to pure YBCO. In comparison to NRs added YBCO nanocomposite samples, NPs added YBCO nanocomposite samples showed higher improvement. Throughout the entire investigated range of applied field, the maximum pinning force was found for 0.5 wt% NPs added composite sample.

    DOI: 10.1016/j.ceramint.2021.08.328

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  • Width dependence of the 0.5 × (2e<sup>2</sup>/h) conductance plateau in InAs quantum point contacts in presence of lateral spin-orbit coupling 査読有り 国際誌

    Das P., Cahay M., Kalita S., Mal S., Jha A.

    Scientific Reports ( Nature Publishing Group )   9 ( 1 )   2019年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)

    The evolution of the 0.5Go (Go = 2e2/h) conductance plateau and the accompanying hysteresis loop in a series of asymmetrically biased InAs based quantum point contacts (QPCs) in the presence of lateral spin-orbit coupling (LSOC) is studied using a number of QPCs with varying lithographic channel width but fixed channel length. It is found that the size of the hysteresis loops is larger for QPCs of smaller aspect ratio (QPC channel width/length) and gradually disappears as their aspect ratio increases. The physical mechanisms responsible for a decrease in size of the hysteresis loops for QPCs with increasing aspect ratio are: (1) multimode transport in QPCs with larger channel width leading to spin-flip scattering events due to both remote impurities in the doping layer of the heterostructure and surface roughness and impurity (dangling bond) scattering on the sidewalls of the narrow portion of the QPC, and (2) an increase in carrier density resulting in a screening of the electron-electron interactions in the QPC channel. Both effects lead to a progressive disappearance of the net spin polarization in the QPC channel and an accompanying reduction in the size of the hysteresis loops as the lithographic width of the QPC channel increases.

    DOI: 10.1038/s41598-019-48380-1

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  • Superconductive REBCO thin films and their nanocomposites: The role of rare-earth oxides in promoting sustainable energy 招待有り 査読有り 国際誌

    Jha A., Matsumoto K.

    Frontiers in Physics ( Frontiers )   7 ( 7 )   82-1 - 82-21   2019年01月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    The lossless transmission of direct electrical currents in superconductors is very often regarded as an "energy superhighway" with greatly enhanced efficiency. With the discovery of high temperature superconductors (HTS) in the late eighties, the prospect of using these materials in efficient and advanced technological applications became very prominent. The elevated operating temperatures as compared to low temperature superconductors (LTS), relaxing cooling requirements, and the gradual development of facile synthesis processes raised hopes for a broad breakthrough of superconductor technology. The impact of superconductor technology on the economy and energy sectors is predicted to be huge if these are utilized on a large scale. The development of superconducting tapes with high critical current density (Jc) is crucial for their use in transmission cables. Many countries these days are running projects to develop wires from these HTS materials and simultaneously field trials are being conducted to assess the feasibility of this technology. These HTS wires can carry electrical currents more than 100 times larger than their conventional counterparts with minimal loss of energy. The increased efficiency of HTS electric power products may result in greatly reduced carbon emissions compared to those resulting from using the conventional alternatives. In order to use the thin films of YBa2Cu3O7-δ (YBCO) and REBCO [RE (rare-earth) = Sm, Gd, Eu etc.], members of the HTS family, for future technological applications, the enhancement of Jc over wide range of temperatures and applied magnetic fields is highly desired. The enhancement of Jc of YBCO and REBCO films has been successfully demonstrated by employing different techniques which include doping by rare-earth atoms, incorporating nanoscale secondary phase inclusions into the REBCO film matrix, decoration of the substrate surface etc. which generate artificial pinning centers (APCs). In this review, the development of the materials engineering aspect that has been conducted over the last two decades to improve the current carrying capability of HTS thin films is presented. The effect of controlled incorporation of APCs through various methods and techniques on the superconducting properties of YBCO and REBCO thin films is presented, heading toward superior performance of such superconducting thin films.

    DOI: 10.3389/fphy.2019.00082

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  • Temperature dependence of critical currents in REBCO thin films with artificial pinning centers 査読有り 国際誌

    Matsumoto K., Nishihara M., Kimoto T., Horide T., Jha A., Yoshida Y., Awaji S., Ichinose A.

    Superconductor Science and Technology ( Institute of Physics )   30 ( 10 )   2017年09月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)

    © 2017 IOP Publishing Ltd. Conventionally, δT c type (order parameter modulation) and δl type (mean free path modulation) pinning mechanisms have been proposed to explain the temperature dependence of the flux pinning of superconducting materials. According to previous studies, it is assumed that the temperature dependence of J c of REBa 2 Cu 3 O 7 (REBCO, RE =Y, Gd, Sm, etc) films without artificial pinning centers (APCs) is δl type, but it is unidentified when APCs are introduced into the films. In this paper, GdBCO thin films doped with BaHfO 3 (BHO) deposited on LaAlO 3 substrates by pulsed laser deposition were studied. A target exchange method was used to alternately ablate two targets of pure GdBCO and BHO for introducing nanorods as APCs into GdBCO films. Since the insulative BHO acts as a strong pinning center, the δT c pinning mechanism is expected for the temperature dependence of J c of these thin films. However, the experimental results showed that the J c of the films with BHO nanorods was determined by the δl pinning mechanism over a wide temperature range. In order to explain these unexpected results, we examined the pinning mechanism by nanorods based on a resultant pinning force model.

    DOI: 10.1088/1361-6668/aa835b

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  • Isotropic enhancement in the critical current density of YBCO thin films incorporating nanoscale Y<inf>2</inf>BaCuO<inf>5</inf>inclusions 査読有り 国際誌

    Jha A., Matsumoto K., Horide T., Saini S., Mele P., Ichinose A., Yoshida Y., Awaji S.

    Journal of Applied Physics ( American Institute of Physics )   122 ( 9 )   2017年09月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    © 2017 Author(s). The effect of incorporation of nanoscale Y 2 BaCuO 5 (Y211) inclusions on the vortex pinning properties of YBa 2 Cu 3 O 7-δ (YBCO or Y123) superconducting thin films is investigated in detail on the basis of variation of critical current density (J C ) with applied magnetic field and also with the orientation of the applied magnetic field at two different temperatures: 77 K and 65 K. Surface modified target approach is employed to incorporate nanoscale Y211 inclusions into the superconducting YBCO matrix. The efficiency of Y211 nanoinclusions in reducing the angular anisotropy of critical current density is found to be significant. The observed angular dependence of the critical current density is discussed on the basis of mutually occupied volume by a vortex and spherical and/or planar defect. A dip in J C near the ab-plane is also observed which has been analyzed on the basis of variation of pinning potential corresponding to a spherical (3-D) or planar (2-D) pinning center and has been attributed to a reduced interaction volume of the vortices with a pinning center and competing nature of the potentials due to spherical and planar defects.

    DOI: 10.1063/1.5001273

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  • Nanostructured Oxide Thin Films for Sustainable Development 査読有り 国際誌

    Mele P., Singh S., Saini S., Jha A., Adam M.

    Procedia Engineering ( Elsevier )   171   201 - 206   2017年01月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)

    © 2017 The Authors. In the effort to emancipate mankind from fossil fuels dependence and minimize the CO2 emissions, efficient transport and conversion of energy is required. Advanced materials such as superconductors and thermoelectrics are expected to play an important role in sustainable science and development. We propose an overview of our recent progress on nanostructured thin films of superconducting and thermoelectric oxides. Superconducting properties of YBa2Cu3Ox and thermoelectric properties of Al-doped ZnO are described in relation to preparation techniques, experimental conditions, substrates used, structure and morphology. We especially discuss a nanoengineering approach for the enhancement of energy transport and energy conversion efficiency of oxide thin films compared to their corresponding counterpart of bulk materials.

    DOI: 10.1016/j.proeng.2017.01.327

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  • Effect of simultaneous addition of 1D and 3D artificial pinning centers in hybrid YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-x</inf>multilayers 査読有り 国際誌

    Mele P., Adam M., Suzuki T., Yoshida Y., Awaji S., Ichinose A., Saini S., Jha A., Matsumoto K.

    Science of Advanced Materials ( American Scientific Publishers )   9 ( 6 )   1042 - 1050   2017年01月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)

    © 2017 by American Scientific Publishers. The nanoengineering approach by PLD method can produce a variety of complex nanocomposite oxide thin films with unique properties for sustainable applications. We report on the epitaxial growth and superconducting properties of YBa 2 Cu 3 O 7-x (YBCO) multilayers incorporating BaSnO 3 (BSO) nanorods and Y 2 O 3 nanoparticles at the same time in order to combine the advantages of both columnar (1D, BSO) and isotropic (3D, Y 2 O 3 ) pinning with the purpose of enhance the pinning force of the films for a wide range of applications in large external magnetic fields. Multilayered films, alternating YBCO+Y 2 O 3 and YBCO+BSO layers were grown in pulsed laser deposition chamber by switching a surface-modified YBCO+~2A% Y 2 O 3 target and a mixed YBCO+4 wt% BSO target. Different combinations for films' growth have been tried via varying the thickness of the alternating layers. The best result was obtained with the combination [(90 nm YBCO +BSO)/(30 nm YBCO+Y 2 O 3 )]×3 presenting a maximum global pinning force F max p = 17.6 GN/m 3 (77 K, 2.2 T, B//c), more than 3 times larger than for typical pure YBCO films. These results demonstrate that the nanoengineering approach is at very advanced level: satisfactory control of nanodefects size and distribution was achieved. At the end, a renewed approach based on the Ginzburg-Landau single vortex theory is used to discuss the contributions of 1D, 3D and 1D+3D APCs to the global pinning force of the hybrid multilayers.

    DOI: 10.1166/sam.2017.2848

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  • Controlling the Critical Current Anisotropy of YBCO Superconducting Films by Incorporating Hybrid Artificial Pinning Centers 査読有り 国際誌

    Jha A., Matsumoto K., Horide T., Saini S., Mele P., Ichinose A., Yoshida Y., Awaji S.

    IEEE Transactions on Applied Superconductivity ( IEEE )   26 ( 3 )   2016年04月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    © 2016 IEEE. BaSnO 3 (BSO) nanocolumns and Y 2 BaCuO 5 (Y211) nanoparticles have been successfully incorporated into YBCO thin films by premixed and surface-modified target approach. The effect of these artificially incorporated nanostructures on the vortex pinning properties of YBCO films is investigated based on the variation of critical current density (J C ) with applied magnetic field and its variation with respect to the orientation of the applied magnetic field at two different temperatures: 77 and 65 K. The incorporation of Y211 nanoparticles into both YBCO and YBCO + BSO2% films results in improved J C -H characteristics, which is reflected in the enhanced pinning force density (F p ) values. The angular dependent J C measurement reveals that the YBCO film containing BSO nanocolumns exhibits J C peak along the c-axis, whereas the film containing Y211 nanoparticles exhibits isotropic enhancement in the J C values along the entire investigated angular regime. The YBCO film consisting of both kinds of nanostructures (BSO nanocolumns together with Y211 nanoparticles), on the other hand, exhibits mixed characteristics of different kinds of pinning: strong c-axis J C peak together with isotropically enhanced J C in the intermediate angular regime. A possible vortex pinning mechanism due to different kinds of artificially incorporated nanostructures is also discussed.

    DOI: 10.1109/TASC.2016.2525989

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  • Critical Current Properties in Longitudinal Magnetic Field of YBCO Superconductor with APC 査読有り 国際誌

    Kido R., Kiuchi M., Otabe E., Matsushita T., Jha A., Matsumoto K.

    Physics Procedia ( Elsevier )   81   117 - 120   2016年01月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)

    The critical current density (J c ) properties of the Artificial Pinning Center (APC) introduced YBa 2 Cu 3 O 7 (YBCO) films in the longitudinal magnetic field were measured. Y 2 O 3 or Y 2 BaCuO 5 (Y211) was introduced as APCs to YBCO, and YBCO films with APC were fabricated on SrTiO 3 single crystal substrate. The sizes of Y 2 O 3 and Y211 were 5 - 10 nm and 10 - 20 nm, respectively. As a result, J c enhancement in the longitudinal magnetic field was observed in Y 2 O 3 introduced YBCO films. However, it was not observed in Y211 introduced YBCO films. Therefore, it was considered that J c properties in the longitudinal magnetic field were affected by introducing of small size APC, and it was necessary that APC does not disturb the current pathway in the superconductor.

    DOI: 10.1016/j.phpro.2016.04.012

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  • Tailoring the vortex pinning strength of YBCO thin films by systematic incorporation of hybrid artificial pinning centers 査読有り 国際誌

    Jha A., Matsumoto K., Horide T., Saini S., Mele P., Ichinose A., Yoshida Y., Awaji S.

    Superconductor Science and Technology ( Institute of Physics )   28 ( 11 )   2015年10月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    © 2015 IOP Publishing Ltd. The effect of hybrid (columnar and spherical together) artificial pinning centers (APCs) on the vortex pinning properties of YBa 2 Cu 3 O 7-δ (YBCO) thin films is investigated in detail on the basis of variation of critical current density (J C ) with applied magnetic field and also with the orientation of the applied magnetic field at 65 K and 77 K. Premixed YBCO + BaSnO 3 composite targets are used for the deposition of the YBCO films which consist of self-assembled BaSnO 3 nanocolumns (1D APCs); on the other hand, for the deposition of the YBCO films with hybrid APCs (BaSnO 3 nanocolumns together with Y 2 O 3 nanoparticles), the surface of the premixed YBCO + BaSnO 3 composite targets are modified by putting a thin Y 2 O 3 sectored piece on the premixed YBCO + BaSnO 3 composite targets by means of silver paste. F pmax value increases systematically with incorporation of 1D and 1D and 3D APCs and it also shifts towards higher applied magnetic fields. Films with 1D APCs exhibit a strong J C peak at Θ = 0° (H//c-axis) whereas films consisting of hybrid APCs exhibit enhanced J C at all the investigated angular regimes. A possible mechanism of vortex pinning in samples with hybrid APCs is also discussed suggesting the role of 1D and 3D APCs.

    DOI: 10.1088/0953-2048/28/11/114004

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  • Irreversibility fields and critical current densities in strongly pinned YBa&lt;inf&gt;2&lt;/inf&gt;Cu&lt;inf&gt;3&lt;/inf&gt;O&lt;inf&gt;7-x&lt;/inf&gt; films with artificial pinning centers 査読有り 国際誌

    Matsumoto K., Horide T., Jha A., Mele P., Yoshida Y., Awaji S.

    IEEE Transactions on Applied Superconductivity ( IEEE )   25 ( 3 )   2015年06月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)

    © 2002-2011 IEEE. We propose a microscopic approach to derive angular dependent critical current density J < inf > c < /inf > (θ) of YBCO films with c-axis correlated nanorods, based on the energy gain by pinning. Results are in good agreement with experimental ones. Irreversibility fields and J < inf > c < /inf > in YBa < inf > 2 < /inf > Cu < inf > 3 < /inf > O < inf > 7-x < /inf > thin films containing segmented BaSnO < inf > 3 < /inf > nanorods are systematically changed by selection of nanorod length and its spacing, and the variations are explained by the 'harmonic oscillator' approach based on the Bose glass state. Analysis of pinning energies and J < inf > c < /inf > indicates that stacked BSO nanorod segments in line behave as single columnar with a smaller diameter pin for Bc, in contrast, as nanoparticle pins for Bab.

    DOI: 10.1109/TASC.2015.2396358

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  • Systematic variation of hybrid APCs into YBCO thin films for improving the vortex pinning properties 査読有り 国際誌

    Jha A., Matsumoto K., Horide T., Saini S., Mele P., Yoshida Y., Awaji S.

    IEEE Transactions on Applied Superconductivity ( IEEE )   25 ( 3 )   2015年06月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    © 2002-2011 IEEE. The effect of hybrid (columnar and spherical) artificial pinning centers (APCs) on the vortex pinning properties of YBCO thin films is studied in this paper on the basis of variation of critical current density J C with applied magnetic field and also with the orientation of the applied magnetic field. YBCO+BSO3% composite target is used for preparing film with 1-D (columnar) APCs, whereas the same composite target is modified by putting two differently sized (2.2 area% and 3 area%) Y 2 O 3 sectored pieces for preparing films having different concentrations of 3-D (spherical) APCs along with 1-D APCs. Film consisting of only 1-D APCs exhibits enhanced in-fieldJ C values as compared to the one without any APC, and the ones consisting of hybrid APCs exhibit even betterJ C -B characteristics with increase in the fraction of 3-D APCs. F pmax . values increase systematically with incorporation of 1-D and 1-D + 3-D APCs, and it also shifts toward higher applied magnetic fields. Film with 1-D APCs exhibits strongJ C peak at Θ = 0° (H//c-axis), whereas films consisting of hybrid APCs exhibit enhancedJ C at all the investigated angular regime. A possible mechanism of vortex pinning in samples with hybrid APCs is also discussed, suggesting the role of 1-D and 3-D APCs.

    DOI: 10.1109/TASC.2014.2380817

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  • Tuning the microstructure and vortex pinning properties of YBCO-based superconducting nanocomposite films by controlling the target rotation speed 査読有り 国際誌

    Jha A., Matsumoto K., Horide T., Saini S., Mele P., Yoshida Y., Awaji S.

    Superconductor Science and Technology ( Institute of Physics )   27 ( 2 )   2014年02月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    We report the controlled incorporation of perovskite, BaSnO 3 (BSO), and double-perovskite, YBa 2 NbO 6 (YBNO), nanocolumnar structures into a YBa 2 Cu 3 O 7 -δ (YBCO) film matrix by controlling the target rotation speed. A surface modified target approach has been employed to deposit YBCO+BSO and YBCO+YBNO nanocomposite films using a laser ablation technique. The effect of target rotation speed on the microstructure and subsequently on the superconducting properties has been studied in detail. The density of BSO and YBNO nanocolumnar structures is found to depend on the target rotation speed, which subsequently affects the vortex pinning properties of the superconducting films in the absence and presence of applied magnetic fields. Three rotation speeds, 3, 2 and 1 s/rot., have been attempted in this study. Compared to pure YBCO, the YBCO+BSO and YBCO+YBNO nanocomposite films exhibit superior in-field critical current density (J C ) and also exhibit a strong J C peak for H ∥ c-axis, indicating strong c-axis pinning. The irreversibility line has also been found to improve significantly in the nanocomposite films. For both the target combinations (YBCO+BSO and YBCO+YBNO), the target rotation speed of 2 s/rot. has been found to give the optimum superconducting properties. © 2014 IOP Publishing Ltd.

    DOI: 10.1088/0953-2048/27/2/025009

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  • Influence of interfacial LSMO nanoparticles/layer on the vortex pinning properties of YBCO thin film 査読有り 国際誌

    Alok K. Jha, Neeraj Khare and R. Pinto

    Journal of Superconductivity and Novel Magnetism ( Springer )   27 ( 4 )   1021 - 1026   2014年01月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    YBa 2 Cu 3 O 7-δ (YBCO) thin films have been deposited on bare and La 0.67 Sr 0.33 MnO 3 (LSMO) modified single crystal SrTiO 3 (STO) substrates. The effect of randomly distributed ferromagnetic LSMO nanoparticles and a complete LSMO layer, present at STO/YBCO interface, on the superconducting properties of YBCO thin films has been investigated by temperature dependent magnetization studies. The YBCO thin film on LSMO nanoparticles decorated STO substrate shows significant improvement in the critical current density and pinning force density as compared to the YBCO thin film deposited on bare STO substrate and this improvement is more significant at higher applied magnetic field. However, the LSMO/YBCO bilayer showed the improved flux pinning properties only up to a magnetic field of 1.5 T above which it deteriorates. In the case of LSMO/YBCO bilayer, the underlying LSMO layer gives rise to magnetic inhomogeneities due to domain structure, which leads to improved flux pinning properties limited to lower field. However, in the case of LSMO nanoparticles decorated substrate, the presence of LSMO nanoparticles at YBCO/STO interface seems to introduce magnetic inhomogeneities as well as structural defects, which might be acting as correlated pinning sites leading to improved flux pinning properties of the YBCO thin film over a wide range of applied magnetic field. © 2013 Springer Science+Business Media New York.

    DOI: 10.1007/s10948-013-2384-0

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  • Comparison of flux pinning mechanism in laser ablated YBCO and YBCO:BaZrO 3 nanocomposite thin films 査読有り 国際誌

    Alok K. Jha, Neeraj Khare and R. Pinto

    Journal of Superconductivity and Novel Magnetism ( Springer )   25 ( 2 )   377 - 380   2012年02月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    Thin films of YBCO and YBCO:BaZrO 3 (BZO) nanocomposite have been deposited using the pulsed laser deposition technique. Substantial increase in critical current density (J C ) and pinning force density (F p ) of the nanocomposite thin films was observed. The possible pinning mechanism in YBCO:BZO nanocomposite thin films has been explored and compared with the pinning mechanism in pure YBCO thin film by studying the variation of J C with magnetic field (B) and temperature. In the intermediate field regime (0.1-1 T), J C follows B -α with nearly similar values of α for YBCO and YBCO:BZO nanocomposite thin films indicating similar pinning mechanism in both thin films. The variation of J C with reduced temperature (t = T/T C ) has been studied for both the films and it was observed that the mechanism of pinning in both YBCO and YBCO:BZO thin films is similar (δT C pinning). The observed enhanced values of J C and F p of the nanocomposite thin film is attributed to the presence of BZO nanoparticles, which induces more defects due to lattice mismatch between YBCO and BZO leading to improved flux pinning properties of the nanocomposite thin film. © Springer Science+Business Media, LLC 2011.

    DOI: 10.1007/s10948-011-1321-3

    Scopus

    その他リンク: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84860339083&origin=inward

  • Interface engineering using ferromagnetic nanoparticles for enhancing pinning in YBa <inf>2</inf>Cu <inf>3</inf>O <inf>7-δ</inf> thin film 査読有り 国際誌

    Alok K. Jha, Neeraj Khare and R. Pinto

    Journal of Applied Physics ( American Institute of Physics )   110 ( 11 )   2011年12月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    Thin films of YBCO have been deposited on bare and La 0.67 Sr 0.33 MnO 3 (LSMO) nanoparticle decorated single crystal SrTiO 3 (STO) substrates. The effect of ferromagnetic LSMO nanoparticles, present at the substrate/film interface, on the superconducting properties of YBa 2 Cu 3 O 7- (YBCO) thin film has been investigated by temperature dependent magnetization studies. The YBCO thin film on LSMO decorated STO substrate shows significant improvement in the critical current density and pinning force density as compared to the YBCO thin film deposited on the undecorated substrate, and this improvement is more significant at higher applied magnetic field. The presence of LSMO nanoparticles at YBCO/STO interface seems to introduce structural defects, which might be in the form of threading dislocations along the c-axis acting as correlated pinning centers leading to improved flux pinning properties of the YBCO thin film. The LSMO nanoparticles are ferromagnetic, which can also act as magnetic pinning centers and may result in the enhancement of flux pinning properties of the YBCO thin film deposited on the LSMO decorated STO substrate. © 2011 American Institute of Physics.

    DOI: 10.1063/1.3665874

    Scopus

    その他リンク: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84859353730&origin=inward

  • Enhanced critical current density in YBa2Cu3O 7-δ thin film deposited on La0.67Sr 0.33MnO3 decorated SrTiO3 substrates 査読有り 国際誌

    Alok K. Jha, Neeraj Khare and R. Pinto

    Physica C: Superconductivity and its Applications ( Elsevier )   471 ( 21-22 )   1154 - 1157   2011年11月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    Thin films of YBa 2 Cu 3 O 7-δ (YBCO) have been deposited on undecorated and La 0.67 Sr 0.33 MnO 3 (LSMO) nanoparticles decorated single crystal SrTiO 3 (STO) substrate using laser ablation technique and their flux pinning characteristics have been compared using temperature dependent magnetization studies. Significant improvement in the critical current density of YBCO thin film has been observed even at higher applied magnetic field (∼7 T). The improved flux pinning properties of YBCO thin films deposited on LSMO decorated STO substrate has been attributed to the presence of ferromagnetic LSMO nanoparticles at the substrate/film interface which seem to be acting as artificially generated magnetic pinning centres leading to improved flux pinning properties. © 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2011.05.147

    Scopus

    その他リンク: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=80055004962&origin=inward

  • Enhanced flux pinning in pulsed laser deposited y Ba2Cu 3O7-δ: BaTiO3 nanocomposite thin films 査読有り 国際誌

    Alok K. Jha, Neeraj Khare and R. Pinto

    Solid State Communications ( Elsevier )   151 ( 20 )   1447 - 1451   2011年10月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    The effect of incorporation of BaTiO 3 (BTO) nanoparticles on the flux pinning properties of pulsed laser deposited YBCO:BTO thin films was studied. Substantial increase in the critical current density ( JC ) and the pinning force density ( Fp ) of the nanocomposite thin films was observed. At 77 K, and zero applied magnetic field, the value of JC for YBCO and YBCO:BTO (2%) thin films were 2.93 MAcm 2 and 6.43 MAcm 2 , respectively. At the same temperature and an applied magnetic field of 4 T, the value of JC increases from 3.6×10 4 Acm 2 for YBCO thin film to 2.7×10 5 Acm 2 for YBCO:BTO (2%) nanocomposite thin film. The study of temperature and field dependence of J C of YBCO and YBCO:BTO thin films indicates similar type of pinning. The lattice mismatch between YBCO and BTO seems to introduce more defects resulting in the improvement of flux pinning properties. © 2011 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.ssc.2011.07.004

    Scopus

    その他リンク: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=80052268467&origin=inward

  • Enhanced flux pinning in laser ablated YBCO:BaTiO3 nanocomposite thin film 査読有り 国際誌

    Alok K. Jha, Neeraj Khare and R. Pinto

    AIP Conference Proceedings ( American Institute of Physics )   1349 ( PART A )   919 - 920   2011年09月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)

    India   Manipal University, Manipal, India   2010年12月26日  -  2010年12月30日

    The effect of incorporation of BaTiO 3 (BTO) nanoparticles on the flux pinning properties of laser deposited YBCO:BTO thin films has been studied. Substantial increase in critical current density (J C ) and pinning force density of the nanocomposite thin films was observed. The study of temperature and field dependence of J C of YBCO and YBCO:BTO thin films indicates similar type of pinning. The lattice mismatch between YBCO and BTO seems to introduce more defects resulting in improved flux pinning properties. © 2011 American Institute of Physics.

    DOI: 10.1063/1.3606158

    Scopus

    その他リンク: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=80052507125&origin=inward

  • Investigation of flux pinning properties of YBCO:BaZrO<inf>3</inf> composite superconductor from temperature dependent magnetization studies 査読有り 国際誌

    Alok K. Jha and Neeraj Khare

    Journal of Magnetism and Magnetic Materials ( Elsevier )   322 ( 18 )   2653 - 2657   2010年09月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    Magnetization studies of YBCO:BaZrO 3 composite superconductor have been done over a wide range of temperature and applied magnetic field using MPMS SQUID VSM and the results are compared with that of pure YBCO. The analysis of the observed results indicate that there is considerable improvement in the values of critical current density (J C ) and pinning force density (F p ) of YBCO:BaZrO 3 composite samples as compared to pure YBCO sample in the entire investigated range of applied magnetic field and temperatures ranging from 4 to 77 K. The variation of J C with reduced temperature t (=T/T C ) for the composite samples has been found to be similar to that of pure YBCO sample indicating similar nature of the vortex interaction with pinning centres in both pure and composite samples. The enhancement in the value of J C and F p in the composite samples as compared to pure YBCO sample has been attributed to the increased defect density in the composite samples due to the presence of BZO particles in YBCO matrix. © 2010 Elsevier B.V.

    DOI: 10.1016/j.jmmm.2010.04.002

    Scopus

    その他リンク: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=77954219202&origin=inward

  • Strongly enhanced pinning force density in YBCO:BaTiO3 nanocomposite superconductor 査読有り 国際誌

    Alok K. Jha and Neeraj Khare

    Physica C: Superconductivity ( Elsevier )   ( 469 )   810 - 813   2009年07月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    DOI: 10.1016/j.physc.2009.05.008

  • Single crystalline superconducting MgB2 nanowires 査読有り 国際誌

    Alok K. Jha and Neeraj Khare

    Superconductor Science and Technology ( Institute of Physics )   ( 22 )   075017-1 - 075017-3   2009年06月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)

    DOI: 10.1088/0953-2048/22/7/075017

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著書

  • Surfaces and Interfaces of Metal Oxide Thin Films, Multilayers, Nanoparticles and Nano-composites

    Alok K. Jha and Kaname Matsumoto(共著)

    Springer Nature  2021年06月  ( ISBN:978-3-030-74072-6

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    記述言語:英語

    In this book, chapter 9 which is named as "Interfaces in REBCO based nanocomposite thin films and their contribution to vortex pinning" is contributed by us.

    In this chapter, the evolution of the various interfaces in REBCO nanocomposite thin films through incorporation of secondary phase nanoinclusions and their contribution to vortex pinning are presented.

  • Superconductivity: From Materials Science to Practical Applications

    P. Mele, K. Prassides, C. Tarantini, A. Palau, P. Badica, A. K. Jha, T. Endo(共著)

    Springer Nature  2019年08月  ( ISBN:978-3-030-23302-0

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    記述言語:英語

  • Control of Vortex Pinning in YBCO Thin Films by Incorporating APCs Through Surface Modified Target Approach

    Alok K. Jha and Kaname Matsumoto(共著 ,  範囲: 53-73)

    Springer Nature  2019年08月  ( ISBN:978-3-030-23302-0

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    総ページ数:369   記述言語:英語

    In this book, chapter 3 named as "Control of Vortex Pinning in YBCO Thin Films by Incorporating APCs Through Surface Modified Target Approach" is contributed by us.

    In this chapter, the use of surface modified target method to introduce different kinds of APCs into YBCO thin films is presented. These APCs are effective in improving the vortex pinning properties of YBCO thin films for different range of applied magnetic field and its orientation depending upon their geometry and density.

口頭発表・ポスター発表等

  • Vortex pinning and critical current densities in GdBCO thin films with CaHfO3 nanoinclusions

    Alok K. Jha

    East Asia Symposium on Superconductor Electronics (EASSE) 2023  Yamagata University and Okayama University

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    開催期間: 2023年03月27日 - 2023年03月29日   記述言語:英語   開催地:Okayama Convention Center   国名:日本国  

    We have studied the incorporation of CaHfO3 nanoinclusions inside GdBCO superconducting film matrix and subsequently the vortex pinning properties of the nanocomposite films. In this paper, the structural, microstructural and transport properties of GdBCO thin films incorporating varying concentrations of CaHfO3 are discussed.

    その他リンク: https://www.okayama-u.ac.jp/user/eng_aemt/EASSE2023/index.html

  • Search for superconductivity in Ir doped LSMO thin films

    Alok K. Jha

    70th JSAP Spring Meeting  2023年03月  Japan Society of Applied Physics

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    開催期間: 2023年03月15日 - 2023年03月18日   記述言語:英語   開催地:Sophia University   国名:日本国  

    In this study, we report the fabrication of Ir doped LSMO thin films on single crystal SrTiO3 and LSAT substrates using pulsed laser deposition technique and their structural, microstructural and electrical characterization.

    その他リンク: https://meeting.jsap.or.jp/english/program

  • Observation of superconducting transition in MTO/STO heteroepitaxial multilayer films

    Alok K. Jha

    70th JSAP Spring Meeting  2023年03月  Japan Society of Applied Physics

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    開催期間: 2023年03月15日 - 2023年03月18日   記述言語:英語   開催地:Sophia University   国名:日本国  

    In this study, the multilayer structures of spinel-type oxides containing transition metals are investigated. We studied the electrical transport properties of spinel MgTi2O4/SrTiO3 multilayer thin films with varying layer thickness and observed the appearance of superconducting transition with varying onset temperatures depending upon the layer thickness.

    その他リンク: https://meeting.jsap.or.jp/english/program

  • Vortex pinning and critical current densities in superconducting REBCO thin films with different nanoscale inclusions 招待有り

    Alok K. Jha

    International Conference on Advanced Materials and Nanotechnology (ICAMN) 2022  2022年12月  Jaypee Institute of Information Technology, INDIA

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    開催期間: 2022年12月22日 - 2022年12月24日   記述言語:英語   開催地:NOIDA, U. P., INDIA   国名:インド  

    The role of different geometries of the artificial pinning centers in pinning the quantized vortices are discussed. Accordingly, their influence on critical current densities of the REBCO thin films are presented.

    その他リンク: http://www.icamn.in/

  • Pinning of quantized vortices in superconducting YBCO thin films with different artificial pinning centers 招待有り

    Alok K. Jha

    Research Seminar Series, Ahmedabad University  2022年08月  School of Arts and Science, Ahmedabad University, India

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    開催期間: 2022年08月24日   記述言語:英語   開催地:Ahmedabad, India   国名:インド  

    In this talk, the developments in improving the superconducting parameters of YBCO over the years were presented. In addition, the structural, microstructural and transport properties of YBCO thin films incorporating different artificial pinning centers were also presented. The evaluation of temperature dependent vortex pinning properties due to various artificial pinning centers have also been discussed.

    その他リンク: https://ahduni.edu.in/academics/schools-centres/school-of-arts-and-sciences/

  • Pinning of quantized vortices in GdBCO thin films by BaHfO3 and CaHfO3 nanoinclusions: a comparative study

    Alok K. Jha

    69th JSAP Spring Meeting  2022年03月  応用物理学会

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    開催期間: 2022年03月22日 - 2022年03月26日   記述言語:英語   開催地:Aoyama Gakuin University, Sagamihara, Japan   国名:日本国  

    We have investigated the incorporation of BaHfO3 and CaHfO3 nanoinclusions in GdBCO superconducting films and subsequently the vortex pinning properties of the nanocomposite films. In this presentation, the comparison was drawn between GdBCO films with BaHfO3 and CaHfO3 nanostructures.

    その他リンク: https://meeting.jsap.or.jp/jsap2022s/english

  • Evolution of REBCO thin films and their role in promoting sustainable energy 招待有り

    Alok K. Jha

    Global Research Efforts on Energy and Nanomaterials (GREEN) 2021  2021年12月  Asia Pacific Society for Materials Research

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    開催期間: 2021年12月17日 - 2021年12月19日   記述言語:英語   開催地:Online (virtual)   国名:中華人民共和国  

    In this talk, the developments in improving the superconducting parameters of REBCO over the years were presented. In addition, the reduction and control of critical current anisotropy of REBCO thin films through
    APC technology have also been addressed.

    その他リンク: https://www.apsmr.org/green-2021/

  • Critical current densities in GdBCO thin films with CaHfO3 nanoinclusions

    Alok K. Jha

    The 34th International Symposium on Superconductivity (ISS 2021)  2021年12月  AIST, Japan

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    開催期間: 2021年11月30日 - 2021年12月02日   記述言語:英語   開催地:AIST, Tsukuba, Japan   国名:日本国  

    We have studied the incorporation of CaHfO3 nanoinclusions inside GdBCO superconducting film matrix and subsequently the vortex pinning properties of the nanocomposite films. In this paper, the structural, microstructural and transport properties of GdBCO thin films incorporating varying concentrations of CaHfO3 have been discussed.

    その他リンク: https://iss2021wlg.jp

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担当授業科目(学内)

  • 2023年度   専門英語Ⅱ

  • 2023年度   専門英語Ⅰ

  • 2023年度   マテリアル工学PBL

  • 2023年度   フロンティア工学実習

  • 2022年度   フロンティア工学実習

  • 2022年度   マテリアル工学PBL

  • 2022年度   専門英語Ⅰ

  • 2022年度   専門英語Ⅱ

  • 2021年度   専門英語Ⅰ

▼全件表示

国際会議開催(学会主催除く)

  • 2021 Virtual Coated Conductors for Applications

    Prof. Kaname Matsumoto, Dr. Teruo Izumi  Japan  2021年10月11日 - 2021年10月15日