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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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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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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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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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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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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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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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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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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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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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

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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

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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

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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

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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

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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

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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

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

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

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/

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.

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