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Sample records for high-tc superconducting films

The Goettingen high-Tc superconductivity research pool: the effects of structure and structural defects on the performance of high-Tc superconductors. Final reports

International Nuclear Information System (INIS)

1992-02-01

The compilation presents the final reports prepared by the various teams of the Goettingen research pool for high-Tc superconductivity. The reports are entitled: Structure and phase transition in high-Tc superconductors (Krebs/Freyhardt). Preparation and critical properties of high-Tc superconductors (Freyhardt/Heinemann/Zimmermann). EMC measurements in high-Tc superconductors (Bormann/Noelting). Phase analysis of the various phases observed in the preparation of high-Tc superconductors (Faupel/Hehenkamp). Positron annihilation in high-Tc superconductors (Hehenkamp). Preparation and characterization of thin films consisting of superconducting oxide ceramics (v. Minnigerode/Samwer). High-Tc superconductivity in monocrystals (Winzer/Beuermann). Microwave conductivity in high-Tc superconductors (Helberg). High-resolution structural analyses in high-Tc superconductors (Kupcik/Bente). Synthesis, structural analyses and spectroscopy of high-Tc superconductors (Bente). Synthesis, monocrystal growing, crystal structure of high-Tc superconductors (Schwarzmann). Ion-beam-aided studies in high-Tc superconductors (Uhrmacher). (orig./MM) [de
Growth and characterization of high-Tc Y1Ba2Cu3O7-x superconducting thin films by chemical vapor deposition

International Nuclear Information System (INIS)

Feng, A.

1992-01-01

In chapter I, the current status of high-Tc superconductors (especially Y 1 Ba 2 Cu 3 O 7-x ), their microstructures and their unique physical properties are reviewed. An introduction to the potential and importance of those high-Tc superconductors in practical applications, especially for the application of YBCO thin films in microelectronics, is given. A general description of the common YBCO thin film fabrication and characterization techniques is also presented in this first chapter. Chapter II describes a new CVD process, temperature-controlled chemical vapor deposition (TC-CVD) for the growth of YBCO superconducting thin films on substrates of practical importance, such as sapphire (Al 2 O 3 ) and on substrates of lattice matched perovskite-type single crystals, such as LaAlO 3 . In order to verify the viability of this new CVD process the qualities of YBCO superconducting thin films were examined by various characterization methods, such as resistivity vs. temperature (R vs. T), scanning electron microscopy (SEM), X-ray diffraction (XRD), and magnetic susceptibility (x) measurements. Chapter III deals with the effect of substrate temperature on the properties of YBCO thin films made by TC-CVD. The principle objective of this study is to raise the transition temperature and critical current densities of CVD YBCO superconducting thin films. Understanding the relations between YBCO film growth process and varying substrate temperatures proved to be crucial in reaching this goal. The authors present the characterization results of YBCO thin films produced by different temperature schemes, to illustrate the importance of varying substrate temperature during the film growth. In chapter IV, the Rutherford backscattering (RBS) channeling technique is described. They have used RBS channeling to characterize the epitaxial YBCO thin film's crystallinity and lattice alignment. Transmission electron microscopy studies are also included
Superconductive properties, interaction mechanisms, materials preparation and electronic transport in high-Tc superconductors

International Nuclear Information System (INIS)

Saemann-Ischenko, G.

1993-01-01

The final report is composed of eight chapters dealing with the following aspects: I. Mixed state, critical currents, anisotropy, intrinsic and extrinsic pinning. II. Microwave properties and far-infrared reflectivity of epitactic HTSC films. III. Hall effect at the states of normal conductivity and superconductivity, magnetoresistance, superconducting fluctuation phenomena. IV. Effects of the nuclear and the electronic energy loss. V. Scanning electron microscopy. VI. p- and n-doped high-Tc superconductors: Charge symmetry and magnetism. VII. Preparation methods. VIII. Electrochemical examinations of HTSC films and HTSC monocrystals at low temperatures. (orig./MM) [de
High Tc superconducting three-terminal device under quasi-particle injection

International Nuclear Information System (INIS)

Hashimoto, K.; Kabasawa, U.; Tonouchi, M.; Kobayashi, T.

1988-01-01

A new type of the current injection type three terminal device was fabricated using the high Tc YBaCuO thin epitaxial films, wherein the hot quasi-particle injection effect on the superconducting current was closely examined. The zero bias drain current was efficiently suppressed by the injection of the hot quasi-particles through the gate electrode. Though it is speculative, a comparison of the experimental results and analyses based on the familiar BCS theory intimates that the main mechanism of the current modulation is the non-equilibrium superconductivity due to accumulation of the excess quasi-particles
Magnetic levitation systems using a high-Tc superconducting bulk magnet

Energy Technology Data Exchange (ETDEWEB)

Ohsaki, Hiroyuki [Dept. of Electrical Engineering, Univ. of Tokyo (Japan); Kitahara, Hirotaka [Dept. of Electrical Engineering, Univ. of Tokyo (Japan); Masada, Eisuke [Dept. of Electrical Engineering, Univ. of Tokyo (Japan)

1996-12-31

Recent development of high-performance high-Tc bulk superconductors is making their application for electromagnetic force use feasible. We have studied electromagnetic levitation systems using high-Tc bulk superconducting material. In this paper, after an overview of superconducting magnetic levitation systems, with an emphasis on high-Tc bulk superconductor applications, experimental results of a high-Tc bulk EMS levitation and FEM analysis results of magnetic gradient levitation using bulk superconductor are described. Problems to be solved for their application are also discussed. (orig.)
Preparation and characterization of high-Tc superconducting thin films with high critical current densities

International Nuclear Information System (INIS)

Vase, P.

1991-08-01

The project was carried out in relation to possible cable and electronics applications of high-T c materials. Laser ablation was used as the deposition technique because of its stoichiometry conservation. Films were made in the YBa 2 Cu 3 O 7 compound due to its relatively simple stoichiometry compared to other High-T c compounds. Much attention was paid to the critical current density. A very high critical current density was reached. By using texture analysis by X-ray diffraction, it was found that films with high critical current densities were epitaxial, while films with low critical current densities contained several crystalline orientations. Four techniques for patterning the films were used - photo lithography and wet etch, laser ablation lithography, laser writing and electron beam lithography and ion milling. Sub-micron patterning has been demonstrated without degradation of the superconducting properties. The achieved patterning resolution is sufficient for preparation of many superconducting components. (AB)
Mechanisms of conventional and high Tc superconductivity

International Nuclear Information System (INIS)

Kresin, V.L.; Morawitz, H.; Wolf, S.A.

1993-01-01

This book gives a careful and objective review of theories of superconductivity in traditional superconductors, organics, and high Tc cuprates. Of course, the authors do still present their own theories of cuprate superconductivity, but only in the final chapter after other possibilities have been discussed. The book should be especially useful for researchers entering the field of high Tc superconductivity. The reviews of photon mediated pairing and strong coupling theory are very welcome, since much of this material has not been reviewed since the classic 1969 volume edited by Parks. In particular the authors dispel the various myths that phonon mediated pairing leads to upper bounds on Tc. In addition to phonon mediated pairing the book discussed in detail pairing due to exchange of acoustic (demon) plasmons, excitons, or magnetic fluctuations. There have been so many diverse mechanisms based on strong correlation and large U Hubbard models that a book like this can only discuss a limited selection of the main contenders. In particular here the emphasis on Fermi liquid based models no doubt reflects the authors' own point of view. A whole chapter discusses the concepts of induced superconductivity, in the proximity effect, and its application to materials with several different electronic subsystems
Pulsed laser deposition of high Tc superconducting thin films

International Nuclear Information System (INIS)

Singh, R.K.; Narayan, J.

1990-01-01

This paper reports on the pulsed laser evaporation (PLE) technique for deposition of thin films characterized by a number of unique properties. Based on the experimental characteristics, a theoretical model is developed which considers the formation and anisotropic three dimensional expansion of the laser generated plasma. This model explains most of the experimental features observed in PLE. We have also employed the PLE technique for in-situ fabrication of YBa 2 Cu 3 O 7 superconducting thin films on different substrates in the temperature range of 500--650 degrees C. At temperatures below 600 degrees C, a biased interposing ring between the substrate and the target was found to significantly improve the superconducting properties. The minimum ion channeling yields were between 3--3.5% for films deposited on (100) SrTiO 3 and (100) LaAlO 3 substrates
Microwave effective surface impedance of structures including a high-Tc superconducting film

International Nuclear Information System (INIS)

Hartemann, P.

1992-01-01

The microwave effective surface impedances of different stacks made of high-temperature superconducting films, dielectric materials and bulk normal metals were computed. The calculations were based on the two-fluid model of superconductors and the conventional transmission line theory. These effective impedances are compared to the calculated intrinsic surface impedances of the stacked superconducting films. The considered superconducting material has been the oxide YBa 2 Cu 3 O 7 epitaxially grown on crystalline substrates (MgO, LaAlO 3 , SrTiO 3 ), the film thickness ranging from a few nm to 1μm. Discrepancies between the effective surface resistances or reactances and the corresponding intrinsic values were determined at 10 GHz for non resonant or resonant structures. At resonance the surface resistance discrepancy exhibits a sharp peak which reaches 10 4 or more in relative value according to the geometry and the used materials. Obviously the effective surface reactance shows also huge variations about the resonance and may be negative. Moreover geometries allowing to obtain an effective resistance smaller than the film intrinsic value have been found. The effects of the resonance phenomenon on the electromagnetic wave reflectivity and reflection phase shift are investigated. Therefore the reported theoretical results demonstrate that the effective surface impedance of YBCO films with a thickness smaller than 500 nm can be very different from the intrinsic film impedance according to the structures. (Author). 3 refs., 10 figs., 2 tabs
Formation of high-Tc YBa2Cu3O(7-delta) films on Y2BaCuO5 substrate

Science.gov (United States)

Wang, W. N.; Lu, H. B.; Lin, W. J.; Yao, P. C.; Hsu, H. E.

1988-07-01

High-Tc superconducting YBa2Cu3O(7-delta) films have been successfully prepared on green Y2BaCuO5 (2115) ceramic substrate. The films have been formed by RF sputtering and screen printing with post annealing at 925 C. Regarding superconducting features, the sharp resistivity drop with Tc onset around 95 K (midpoint 84 K) and 99 K (midpoint 89 K) has been observed for RF sputtered and printed films respectively. Both films show the excellent adhesion towards the 2115 substrate. Powder X-ray diffraction profiles indicate a majority of 1237 phase with preferred orientation for RF sputtered thin film.
Bec Model of HIGH-Tc Superconductivity in Layered Cuprates

Science.gov (United States)

Lomnitz, M.; Villarreal, C.; de Llano, M.

2013-11-01

High-Tc superconductivity in layered cuprates is described in a BCS-BEC formalism with linearly-dispersive s- and d-wave Cooper pairs moving in quasi-2D finite-width layers around the CuO2 planes. This yields a closed formula for Tc involving the layer width, the Debye frequency, the pairing energy and the in-plane penetration depth. The new formula has no free parameters and reasonably reproduces empirical values of superconducting Tcs for 11 different layered superconductors over a wide doping regime including YBCO itself as well as other compounds like LSCO, BSCCO and TBCCO. In agreement with the London formalism, the formula also yields a fair description of the Tc dependence of the lower critical magnetic field in highly underdoped YBCO.
In-situ deposition of YBCO high-Tc superconducting thin films by MOCVD and PE-MOCVD

International Nuclear Information System (INIS)

Zhao, J.; Noh, D.W.; Chern, C.; Li, Y.Q.; Norris, P.E.; Kear, B.; Gallois, B.

1991-01-01

Metal-Organic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T(sub c) greater than 90 K and J(sub c) of approximately 10(exp 4) A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology
On the superconducting phase diagram of high Tc superconductors

International Nuclear Information System (INIS)

de la Cruz, F.

1990-01-01

The tendency of oxide superconductors to show granularity has been pointed out since the beginning of research on superconductivity in this type of materials. Nevertheless, only very recently the full phase diagram and characteristics of the grains have been determined. In this paper, the authors review and discuss the different critical fields and their relation to the transport of superconducting current. The superconducting response of single crystals of High Tc superconductors is discussed. Special attention is devoted to the behavior of the vortex lattice and, in particular, to the recent discovery of the quenching of H c1 in YBaCuO, several degrees below Tc
High Tc screen-printed YBa2Cu3O(7-x) films - Effect of the substrate material

Science.gov (United States)

Bansal, Narottam P.; Simons, Rainee N.; Farrell, D. E.

1988-08-01

Thick films of YBa2Cu3O(7-x) have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni-Al-Ti), and barium tetratitanate (Ba-Ti) substrates by the screen printing technique. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba-Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni-Al-Ti had a Tc (onset) of about 95 K and lost 90 percent of its resistance by about 75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc (onset) of about 96 K, Tc (zero) of about 66 K, and Delta Tc of about 10 K. The best film was obtained on spinel and had Tc (onset) of about 94 K, zero resistance at 81 K, and a transition width of about 7 K.
Critical currents and superconductivity ferromagnetism coexistence in high-Tc oxides

CERN Document Server

Khene, Samir

2016-01-01

The book comprises six chapters which deal with the critical currents and the ferromagnetism-superconductivity coexistence in high-Tc oxides. It begins by gathering key data for superconducting state and the fundamental properties of the conventional superconductors, followed by a recap of the basic theories of superconductivity. It then discusses the differences introduced by the structural anisotropy on the Ginzburg-Landau approach and the Lawrence-Doniach model before addressing the dynamics of vortices and the ferromagnetism-superconductivity coexistence in high-Tc oxides, and provides an outline of the pinning phenomena of vortices in these materials, in particular the pinning of vortices by the spins. It elucidates the methods to improve the properties of superconducting materials for industrial applications. This optimization aims at obtaining critical temperatures and densities of critical currents at the maximum level possible. Whereas the primary objective is the basic mechanisms pushing the superco...
Electronic properties of high-Tc superconductors. The normal and the superconducting state of high-Tc materials. Proceedings

International Nuclear Information System (INIS)

Kuzmany, H.; Mehring, M.; Fink, J.

1993-01-01

The International Winter School on Electronic Properties of High-Temperature Superconductors, held between March 7-14, 1992, in Kirchberg, (Tyrol) Austria, was the sixth in a series of meetings to be held at this venue. Four of the earlier meetings were dedicated to issues in the field of conducting polymers, while the winter school held in 1990 was devoted to the new discipline of high-Tc superconductivity. This year's meeting constituted a forum not only for the large number of scientists engaged in high-Tc research, but also for those involved in the new and exciting field of fullerenes. Many of the issues raised during the earlier winter schools on conducting polymers, and the last one on high-Tc superconductivity, have taken on a new significance in the light of the discovery of superconducting C 60 materials. The Kirchberg meetings are organized in the style of a school where experienced scientists from universities, research laboratories and industry have the opportunity to discuss their most recent results, and where students and young scientists can learn about the present status of research and applications from some of the most eminent workers in their field. In common with the previous winter school on high-Tc superconductors, the present one focused on the electronic properties of the cuprate superconductors. In addition, consideration was given to related compounds which are relevant to the understanding of the electronic structure of the cuprates in the normal state, to other oxide superconductors and to fulleride superconductors. Contributions dealing with their preparation, transport and thermal properties, high-energy spectroscopies, nuclear magnetic resonance, inelastic neutron scattering, and optical spectroscopy are presented in this volume. The theory of the normal and superconducting states also occupies a central position. (orig.)
Electronic Instability at High Flux-Flow Velocities in High-Tc Superconducting Films

DEFF Research Database (Denmark)

Doettinger, S. G.; Huebener, R. P.; Gerdemann, R.

1994-01-01

At high flux-flow velocities in type-II superconductors the nonequilibrium distribution of the quasiparticles leads to an electronic instability and an aburpt switching into a state with higher electric resistivity, as predicted by Larkin and Ovchinnikow (LO). We report the first obervation...... of this effect in a high-temperature superconductor, namely in epitaxial c-axis oriented films of YBa(2)Cu3O(7)-(delta). Using the LO therory, we have extracted from out results the inelastic quasiparticle scattering rare tau(in)(-1), which strongly decreases with decreasing temperature below T-c...
Pressure and high-Tc superconductivity in sulfur hydrides.

Science.gov (United States)

Gor'kov, Lev P; Kresin, Vladimir Z

2016-05-11

The paper discusses fundamentals of record-TC superconductivity discovered under high pressure in sulfur hydride. The rapid increase of TC with pressure in the vicinity of Pcr ≈ 123GPa is interpreted as the fingerprint of a first-order structural transition. Based on the cubic symmetry of the high-TC phase, it is argued that the lower-TC phase has a different periodicity, possibly related to an instability with a commensurate structural vector. In addition to the acoustic branches, the phonon spectrum of H3S contains hydrogen modes with much higher frequencies. Because of the complex spectrum, usual methods of calculating TC are here inapplicable. A modified approach is formulated and shown to provide realistic values for TC and to determine the relative contributions of optical and acoustic branches. The isotope effect (change of TC upon Deuterium for Hydrogen substitution) originates from high frequency phonons and differs in the two phases. The decrease of TC following its maximum in the high-TC phase is a sign of intermixing with pairing at hole-like pockets which arise in the energy spectrum of the cubic phase at the structural transition. On-pockets pairing leads to the appearance of a second gap and is remarkable for its non-adiabatic regime: hydrogen mode frequencies are comparable to the Fermi energy.
Response of high Tc superconducting Josephson junction to nuclear radiation

International Nuclear Information System (INIS)

Ding Honglin; Zhang Wanchang; Zhang Xiufeng

1992-10-01

The development of nuclear radiation detectors and research on high T c superconducting nuclear radiation detectors are introduced. The emphases are the principle of using thin-film and thick-film Josephson junctions (bridge junction) based on high T c YBCO superconductors to detect nuclear radiation, the fabrication of thin film and thick-film Josephson junction, and response of junction to low energy gamma-rays of 59.5 keV emitted from 241 Am and beta-rays of 546 keV. The results show that a detector for measuring nuclear radiation spectrum made of high T c superconducting thin-film or thick-film, especially, thick-film Josephson junction, certainly can be developed
Interface-enhanced high-temperature superconductivity in single-unit-cell FeT e1 -xS ex films on SrTi O3

Science.gov (United States)

Li, Fangsen; Ding, Hao; Tang, Chenjia; Peng, Junping; Zhang, Qinghua; Zhang, Wenhao; Zhou, Guanyu; Zhang, Ding; Song, Can-Li; He, Ke; Ji, Shuaihua; Chen, Xi; Gu, Lin; Wang, Lili; Ma, Xu-Cun; Xue, Qi-Kun

2015-06-01

Recently discovered high-temperature superconductivity in single-unit-cell (UC) FeSe films on SrTi O3 (STO) substrate has stimulated tremendous research interest, both experimental and theoretical. Whether this scenario could be extended to other superconductors is vital in both identifying the enhanced superconductivity mechanism and further raising the critical transition temperature (Tc). Here we successfully prepared single-UC FeT e1 -xS ex(0.1 ≤x ≤0.6 ) films on STO substrates by molecular beam epitaxy and observed U -shaped superconducting gaps (Δ ) up to ˜16.5 meV , nearly ten times the gap value (Δ ˜1.7 meV ) of the optimally doped bulk FeT e0 .6S e0 .4 single crystal (Tc˜14.5 K ). No superconducting gap has been observed on the second UC and thicker FeT e1 -xS ex films at 5.7 K, indicating the important role of the interface. This interface-enhanced high-temperature superconductivity is further confirmed by ex situ transport measurements, which revealed an onset superconducting transition temperature above 40 K, nearly two times higher than that of the optimally doped bulk FeT e0 .6S e0 .4 single crystal. This work demonstrates that interface engineering is a feasible way to discover alternative superconductors with higher Tc.

A review of basic phenomena and techniques for sputter-deposition of high temperature superconducting films

Energy Technology Data Exchange (ETDEWEB)

Auciello, O. (Microelectronics Center of North Carolina, Research Triangle Park, NC (USA) North Carolina State Univ., Raleigh, NC (USA). Dept. of Materials Science and Engineering); Ameen, M.S.; Kingon, A.I.; Lichtenwalner, D.J. (North Carolina State Univ., Raleigh, NC (USA). Dept. of Materials Science and Engineering); Krauss, A.R. (Argonne National Lab., IL (USA))

1990-01-01

The processes involved in plasma and ion beam sputter-deposition of high temperature superconducting thin films are critically reviewed. Recent advances in the development of these techniques are discussed in relation to basic physical phenomena, specific to each technique, which must be understood before high quality films can be produced. Control of film composition is a major issue in sputter-deposition of multicomponent materials. Low temperature processing of films is a common goal for each technique, particularly in relation to integrating high temperature superconducting films with the current microelectronics technology. It has been understood for some time that for Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} deposition, the most intensely studied high-{Tc} compound, incorporation of sufficient oxygen into the film during deposition is necessary to produce as-deposited superconducting films at relatively substrate temperatures. Recent results have shown that with the use of suitable buffer layers, high quality Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} sputtered films can be obtained on Si substrates without the need for post-deposition anneal processing. This review is mainly focussed on issues related to sputter-deposition of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} thin films, although representative results concerning the bismuth and thallium based compounds are included. 143 refs., 11 figs.
A study on the development of high Tc superconducting materials

International Nuclear Information System (INIS)

Won, D. Y.; Hong, G. Y.; Lee, H. G.; Lee, H. J.; Kim, C. J.; Kwon, S. C.; Kim, K. B.; Kang, Y. H.; Chang, I. S.; Choi, M. J.

1992-01-01

The major work of this project aims to develop the frictionless superconducting bearing with a high speed. The high magnetization YBaCuO bulk superconductor was prepared by Quasi-melt process. The frictionless superconducting magnetic bearing standed a rotating bar with a speed of 75,000 rpm, which were operated by an electric controller. The low temperature chemical vapor deposition technique was developed. YBaCuO superconducting film showing a superconductivity above 77K was successfully prepared at 650 deg C. Effect of oxygen partial pressure, substrate, deposition temperature on the film properties were also investigated. (Author)
Oxygen stoichiometry and the high Tc superconducting oxides

International Nuclear Information System (INIS)

Tarascon, J.M.; Bagley, B.G.

1989-01-01

Methods for determining the oxygen content in high Tc materials, such as thermogravimetric analysis and chemical analysis, are discussed. Consideration is given to La-based cuprates, Y-based cuprates, and Bi-based cuprates. Superconducting transition temperatures are analyzed as a function of the Cu(1)-O(4) bond lengths for several different compositions in the Y-based system. 28 references
Metallorganic precursors route for high Tc superconducting materials and related phases

International Nuclear Information System (INIS)

Beltran-porter, D.; Gonzalez, A.; Sanchis, M.J.; Beltran-porter, A.; Ibanez, R.; Sapina, F.

1991-01-01

The adequacy of the precursors approach for high Tc superconducting materials is validated by means of three examples of a new synthesis of mixed oxides which are directly related to the high Tc superconductors. The synthesis temperature is lowered significantly, and the need for extending the classic 'building block' approach is shown. The hypothesis that topochemical reactions from molecular to extended solids are posssible is proven. 28 refs
Superconductivity applications for infrared and microwave devices; Proceedings of the Meeting, Orlando, FL, Apr. 19, 20, 1990

Science.gov (United States)

Bhasin, Kul B.; Heinen, Vernon O.

1990-10-01

Various papers on superconductivity applications for IR and microwave devices are presented. The individual topics addressed include: pulsed laser deposition of Tl-Ca-Ba-Cu-O films, patterning of high-Tc superconducting thin films on Si substrates, IR spectra and the energy gap in thin film YBa2Cu3O(7-delta), high-temperature superconducting thin film microwave circuits, novel filter implementation utilizing HTS materials, high-temperature superconductor antenna investigations, high-Tc superconducting IR detectors, high-Tc superconducting IR detectors from Y-Ba-Cu-O thin films, Y-Ba-Cu0-O thin films as high-speed IR detectors, fabrication of a high-Tc superconducting bolometer, transition-edge microbolometer, photoresponse of YBa2Cu3O(7-delta) granular and epitaxial superconducting thin films, fast IR response of YBCO thin films, kinetic inductance effects in high-Tc microstrip circuits at microwave frequencies.
Quantum and superconducting fluctuations effects in disordered Nb 1- xTa x thin films above Tc

Science.gov (United States)

Giannouri, M.; Papastaikoudis, C.

1999-05-01

Disordered Nb 1- xTa x thin films are prepared with e-gun coevaporation. The influence of the β-phase of tantalum in the critical temperature Tc is observed as a function of the substrate temperature. The measurements of transverse magnetoresistance at various isothermals are interpreted in terms of weak-localization and superconducting fluctuations. From the fitting procedure, the phase breaking rate τφ-1 and the Larkin parameter βL are estimated as a function of temperature. Conclusions about the dominant inelastic scattering mechanisms at various temperature regions as well as for the dominant mechanism of superconducting fluctuations near the transition temperature are extracted.
High-Tc Superconducting Thick-Film Spiral Magnet: Development and Characterization of a Single Spiral Module

National Research Council Canada - National Science Library

McGinnis, W

1997-01-01

The objective of this project was to make characterized and numerically model prototype modules of a new type of superconducting electromagnet based on stacked spirals of superconducting thick films...
High-Tc superconducting microbolometer for terahertz applications

Science.gov (United States)

Ulysse, C.; Gaugue, A.; Adam, A.; Kreisler, A. J.; Villégier, J.-C.; Thomassin, J.-L.

2002-05-01

Superconducting hot electron bolometer mixers are now a competitive alternative to Schottky diode mixers in the terahertz frequency range because of their ultra wideband (from millimeter waves to visible light), high conversion gain, and low intrinsic noise level. High Tc superconductor materials can be used to make hot electron bolometers and present some advantage in term of operating temperature and cooling. In this paper, we present first a model for the study of superconducting hot electron bolometers responsivity in direct detection mode, in order to establish a firm basis for the design of future THz mixers. Secondly, an original process to realize YBaCuO hot electron bolometer mixers will be described. Submicron YBaCuO superconducting structures are expitaxially sputter deposited on MgO substrates and patterned by using electron beam lithography in combination with optical lithography. Metal masks achieved by electron beam lithography are insuring a good bridge definition and protection during ion etching. Finally, detection experiments are being performed with a laser at 850 nm wavelength, in homodyne mode in order to prove the feasibility and potential performances of these devices.
Lead-doped electron-beam-deposited Bi-Sr-Ca-Cu-O superconducting thin films

Energy Technology Data Exchange (ETDEWEB)

Agnihotry, S.A.; Saini, K.K.; Kant, C.; Sharma, C.P.; Ekbote, S.N.; Asthana, P.; Nagpal, K.C.; Chandra, S. (National Physical Lab., New Delhi (India))

1991-03-20

Superconducting thin films of the lead-doped Bi-Sr-Ca-Cu-O system have been prepared on (100) single-crystal SrTiO{sub 3} substrates by an electron beam deposition technique using a single sintered pellet as the evaporation source. As-deposited films are amorphous and non-superconducting; post-deposition annealing at an optimized temperature in air has been found to result in crystalline and superconducting films. The superconducting characteristics of the films have been observed to be sensitive not only to the duration and temperature of post-deposition annealing but also to the lead content and the sintering parameters for the pellet to be used as the evaporation source. A pellet with nominal composition Bi{sub 3}Pb{sub 1}Sr{sub 3}Ca{sub 3}Cu{sub 4}O{sub y} that had been sintered for 200 h zero resistivity Tc{sup 0}=112 K. However, films deposited using such a pellet as the evaporation source had Tc{sup 0} {approx equal} 73-78 K, as had the films deposited from a pellet without any lead. We investigated systematically films deposited from pellets with more lead and sintered for different durations. It is evident from these investigations that pellets with nominal composition Bi{sub 3}Pb{sub 2}Sr{sub 3}Ca{sub 3}Cu{sub 4}O{sub y}, i.e. with an excess of lead, and sintered for about 75 h when used as the evaporation source yield films with Tc{sup 0} {approx equal} 100 K when annealed between 835 and 840deg C for an optimized long duration. The films are characterized by X-ray diffraction and energy-dispersive spectroscopy techniques and have been found to be highly c axis oriented. The effect of lead in promoting a high Tc{sup 0}=110 K phase seems to be similar to that in bulk ceramics. (orig.).
Second international Israeli conference on High Tc Superconductivity

International Nuclear Information System (INIS)

1993-01-01

The superconductivity fields covered in this conference are: theory, applications, devices, flux properties high frequencies, Josephson junctions, magnetism, material sciences and physical properties of superconductors, spectroscopy and resonances and thin films
Critical current of high Tc superconducting Bi223/Ag tapes

NARCIS (Netherlands)

Huang, Y.; ten Haken, Bernard; ten Kate, Herman H.J.

1998-01-01

The magnetic field dependence of the critical current of various high Tc superconducting Bi2223/Ag tapes indicates that the transport current is carried through two paths: one is through weakly-linked grain boundaries (Josephson junctions); another is through well-connected grains. The critical
Use of high-temperature superconducting films in superconducting bearings

International Nuclear Information System (INIS)

Cansiz, A.

1999-01-01

We have investigated the effect of high-temperature superconductor (HTS) films deposited on substrates that are placed above bulk HTSs in an attempt to reduce rotational drag in superconducting bearings composed of a permanent magnet levitated above the film/bulk HTS combination. According to the critical state model, hysteresis energy loss is inversely proportional to critical current density, J c , and because HTS films typically have much higher J c than that of bulk HTS, the film/bulk combination was expected to reduce rotational losses by at least one order of magnitude in the coefficient of fiction, which in turn is a measure of the hysteresis losses. We measured rotational losses of a superconducting bearing in a vacuum chamber and compared the losses with and without a film present. The experimental results showed that contrary to expectation, the rotational losses are increased by the film. These results are discussed in terms of flux drag through the film, as well as of the critical state model
Theory of high-Tc superconducting cuprates based on experimental evidence

International Nuclear Information System (INIS)

Abrikosov, A. A.

1999-01-01

A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of Tc, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc
Analysis of eddy current loss in high-Tc superconducting power cables with respect to various structure of stabilizer

International Nuclear Information System (INIS)

Choi, S. J.; Song, M. K.; Lee, S. J.; Cho, J. W.; Sim, K. D.

2005-01-01

The High-Tc superconducting power cable consists of a multi-layer high-Tc superconducting cable core and a stabilizer which is used to bypass the current at fault time. Eddy current loss is generated in the stabilizer in normal operating condition and affects the whole system. In this paper, the eddy current losses are analyzed with respect to various structure of stabilizer by using opera-3d. Moreover, optimal conditions of the stabilizer are derived to minimize the eddy current losses from the analyzed results. The obtained results could be applied to the design and manufacture of the high-Tc superconducting power cable system.
Internal friction around Tc connected with superconductivity in high Tc superconductors

International Nuclear Information System (INIS)

Wang Yening

1993-01-01

Internal friction and ultrasonic measurements show that there always exists a phase-like transition (PLT) characterized by the jump of lattice parameters at tens degrees above Tc in superconducting YBaCuO, BiSrCaCuO and TlBaCaCuO. Ferroelastic loops and shape memory effect associated with elastic softening invariably occur at the PLT temperature, showing the characteristics of thermoelastic martensitic transition. Internal frictions in KHz of Bi(Pb)SrCaCuO reveal a static hysteretic plateau (Qp -1 ) above Tc that drops linearly with temperature below Tc. The Qp -1 of YBaCuO decreases with decreasing oxygen content. The origin of the hysteretic Qp -1 is attributed to the lattice distortions around the carriers. (orig.)
Quantification of oxygen and carbon in high Tc superconducting films by (α,α) elastic resonance technique

International Nuclear Information System (INIS)

Vizkelethy, G.; Revesz, P.

1993-01-01

The quantification of oxygen and carbon in high-temperature (T c ) superconducting oxide thin films was made by employing elastic resonance in He backscattering analysis. A method combining the oxygen resonance technique and channeling was presented for measuring the nature of the oxygen disorder near the surface and the interface in a YBCO superconducting film grown on an MgO substrate. The oxygen resonance technique was used to quantify the oxygen profiling in the metal/YBCO contacts, showing that Zr and Nb act as sinks to oxygen from YBCO films and are oxidized in the forms Zr/ZrO 2 /YBCO/MgO and Nb 0.2 O/YBCO/MgO after annealing in a vacuum at 350 o C. We combined the carbon and oxygen resonances to determine the carbon contamination and oxygen concentration changes on the YBCO surface after coating and baking the photoresist. Residual carbon on the surface and a thin layer of oxygen depletion near the YBCO surface have been observed. The residual carbon in Bi 2 Sr 2 CaCu 2 O 8 films made by the decomposition of metallo-organic precursors was quantified using carbon resonance. (author)
Superconductivity in the W-Tc and W2C-Tc systems

International Nuclear Information System (INIS)

Giorgi, A.L.

1985-01-01

A series of compositions in the W-Tc, W 2 C-Re and W 2 C-Tc systems were prepared and examined for superconductivity. The crystal structure, lattice parameters and superconducting transition temperatures of the W 2 C-Tc are reported for the first time. Similar measurements were made on the W-Tc and W 2 C-Re systems and the results compared with previous published results for these systems. 7 refs., 2 figs., 2 tabs
High Tc superconducting energy storage systems

Energy Technology Data Exchange (ETDEWEB)

Werfel, Frank [Adelwitz Technologiezentrum GmbH (ATZ), Arzberg-Adelwitz (Germany)

2012-07-01

Electric energy is basic to heat and light our homes, to power our businesses and to transport people and goods. Powerful storage techniques like SMES, Flywheel, Super Capacitor, and Redox - Flow batteries are needed to increase the overall efficiency, stability and quality of electrical grids. High-Tc superconductors (HTS) possess superior physical and technical properties and can contribute in reducing the dissipation and losses in electric machines as motors and generators, in electric grids and transportation. The renewable energy sources as solar, wind energy and biomass will require energy storage systems even more as a key technology. We survey the physics and the technology status of superconducting flywheel energy storage (FESS) and magnetic energy storage systems (SMES) for their potential of large-scale commercialization. We report about a 10 kWh / 250 kW flywheel with magnetic stabilization of the rotor. The progress of HTS conductor science and technological engineering are basic for larger SMES developments. The performance of superconducting storage systems is reviewed and compared. We conclude that a broad range of intensive research and development in energy storage is urgently needed to produce technological options that can allow both climate stabilization and economic development.
A study on the development of high Tc superconducting materials

International Nuclear Information System (INIS)

Won, Dong Yeon; Lee, Hee Gyoun; Kim, Chan Joong

1990-01-01

The microstructure, crystal structure and formation kinetics for the superconducting phases were studied in the lead-doped BiSrCaCuO system. The formation kinetics was also investigated in the samples with different Pb/Bi ratio and it was observed that the 30 % Pb addition is most perferable for the formation of the high T c phase. The formation of the high T c phase was delayed by the excessive addition of Pb. The lattice parameter (c) of the unit cell of both low T c and high T c phases increased with increasing Pb content. Superconducting thin film was sucessfully prepared by chemical vapor deposition (CVD). Film deposited on MgO substrate showed a T c , onset of 85 K and did not reach to zero resistivity down to 77 K. Superconducting 124 phase in Y-system, which is more stable than 123 phase at high temperature showed a T c , onser of 84 K. Additionally, 0.1 mole of Pb, Sn and Ca was substituted for yttrium in 124 phase, respectively. For Pb and Sn-subsituted specimens, 124 phase was formed and for Ca substituted specimen, 124 phase was not formed and revealed no superconductivity down to 77 K. For Sn-substituted specimens, 124 phase was formed but showed no superconductivity down to 77 K. (author)
Imaging the electron-boson coupling in superconducting FeSe films using a scanning tunneling microscope.

Science.gov (United States)

Song, Can-Li; Wang, Yi-Lin; Jiang, Ye-Ping; Li, Zhi; Wang, Lili; He, Ke; Chen, Xi; Hoffman, Jennifer E; Ma, Xu-Cun; Xue, Qi-Kun

2014-02-07

Scanning tunneling spectroscopy has been used to reveal signatures of a bosonic mode in the local quasiparticle density of states of superconducting FeSe films. The mode appears below Tc as a "dip-hump" feature at energy Ω∼4.7kBTc beyond the superconducting gap Δ. Spectra on strained regions of the FeSe films reveal simultaneous decreases in Δ and Ω. This contrasts with all previous reports on other high-Tc superconductors, where Δ locally anticorrelates with Ω. A local strong coupling model is found to reconcile the discrepancy well, and to provide a unified picture of the electron-boson coupling in unconventional superconductors.

Anomalous magnetism of superconducting Mg-doped InN film

Directory of Open Access Journals (Sweden)

P. H. Chang

2016-02-01

Full Text Available We report on the Meissner effect of Mg-doped InN film with superconducting transition onset temperature Tc,onset of 5 K. Mg-doped InN is magnetically ordered and exhibits a simultaneous first-order magnetic and electric transition near 50 K. Its behavior is similar to that of iron-based superconductors. A strong correlation is proposed to exist between structural distortion and superconductivity when Mg is doped into InN. The suppression of magnetic ordering close to Tc by doping is further demonstrated by anisotropic magnetoresistance and M-H measurements. The findings suggest that the superconducting mechanism in the system may not be conventional BCS.
Physical properties of high-Tc superconducting oxides. Modification of tc using organic dopants. Final report. Proprietes physiques d'oxydes supraconducteurs a haute Tc. Modification de tc sous l'effet de dopants organiques

Energy Technology Data Exchange (ETDEWEB)

Brau, A

1993-01-01

An attempt was made to significantly modify the Tc transition temperature of certain copper-based superconducting oxides by introducing organic or mineral dopants, and to study the mobility of 300K-carriers in crystallized tallium-base superconducting oxides. Since the critical transition temperature of superconducting oxides is highly influenced by the density of the free carriers they contain, the authors tried making superconducting powders react with either an organic electron acceptor or a mineral compound. The goal was to increase the density of the holes by altering the copper's degree of oxidation. Their preparatory work showed a direct charge-transfer reaction between the electron-donor copper and the acceptor TCNQ and studied the degree to which the electron acceptor can alter the copper's oxidation. Initial results also showed that dopants can affect superconducting Tc and the course of R(T) curves.
Growth of YBCO superconducting thin films on CaF sub 2 buffered silicon

CERN Document Server

Bhagwat, S S; Patil, J M; Shirodkar, V S

2000-01-01

CaF sub 2 films were grown on silicon using the neutral cluster beam deposition technique. These films were highly crystalline and c-axis oriented. Superconducting YBCO thin films were grown on the Ca F sub 2 buffered silicon using the laser ablation technique. These films showed T sub c (onset) at 90 K and Tc(zero) at 86 K. X-ray diffraction analysis showed that the YBCO films were also oriented along the c-axis.
High-Tc superconducting electric motors

International Nuclear Information System (INIS)

Schiferl, R.; Stein, J.

1992-01-01

In this paper, the advantages and limitations of using superconductors in motors are discussed. A synchronous motor with a high temperature superconducting field winding for pump and fan drive applications is described and some of its unique design features are identified. A 10,000 horsepower superconducting motor design is presented. The critical field and current density requirements for high temperature superconducting wire in motors is discussed. Finally, recent progress in superconducting wire performance is presented
High quality superconducting titanium nitride thin film growth using infrared pulsed laser deposition

Science.gov (United States)

Torgovkin, A.; Chaudhuri, S.; Ruhtinas, A.; Lahtinen, M.; Sajavaara, T.; Maasilta, I. J.

2018-05-01

Superconducting titanium nitride (TiN) thin films were deposited on magnesium oxide, sapphire and silicon nitride substrates at 700 °C, using a pulsed laser deposition (PLD) technique, where infrared (1064 nm) pulses from a solid-state laser were used for the ablation from a titanium target in a nitrogen atmosphere. Structural studies performed with x-ray diffraction showed the best epitaxial crystallinity for films deposited on MgO. In the best films, superconducting transition temperatures, T C, as high as 4.8 K were observed, higher than in most previous superconducting TiN thin films deposited with reactive sputtering. A room temperature resistivity down to ∼17 μΩ cm and residual resistivity ratio up to 3 were observed in the best films, approaching reported single crystal film values, demonstrating that PLD is a good alternative to reactive sputtering for superconducting TiN film deposition. For less than ideal samples, the suppression of the film properties were correlated mostly with the unintended incorporation of oxygen (5–10 at%) in the film, and for high oxygen content films, vacuum annealing was also shown to increase the T C. On the other hand, superconducting properties were surprisingly insensitive to the nitrogen content, with high quality films achieved even in the highly nitrogen rich, Ti:N = 40/60 limit. Measures to limit oxygen exposure during deposition must be taken to guarantee the best superconducting film properties, a fact that needs to be taken into account with other deposition methods, as well.
Superconducting properties of iron chalcogenide thin films

Directory of Open Access Journals (Sweden)

Paolo Mele

2012-01-01

Full Text Available Iron chalcogenides, binary FeSe, FeTe and ternary FeTexSe1−x, FeTexS1−x and FeTe:Ox, are the simplest compounds amongst the recently discovered iron-based superconductors. Thin films of iron chalcogenides present many attractive features that are covered in this review, such as: (i easy fabrication and epitaxial growth on common single-crystal substrates; (ii strong enhancement of superconducting transition temperature with respect to the bulk parent compounds (in FeTe0.5Se0.5, zero-resistance transition temperature Tc0bulk = 13.5 K, but Tc0film = 19 K on LaAlO3 substrate; (iii high critical current density (Jc ~ 0.5 ×106 A cm2 at 4.2 K and 0 T for FeTe0.5Se0.5 film deposited on CaF2, and similar values on flexible metallic substrates (Hastelloy tapes buffered by ion-beam assisted deposition with a weak dependence on magnetic field; (iv high upper critical field (~50 T for FeTe0.5Se0.5, Bc2(0, with a low anisotropy, γ ~ 2. These highlights explain why thin films of iron chalcogenides have been widely studied in recent years and are considered as promising materials for applications requiring high magnetic fields (20–50 T and low temperatures (2–10 K.
Low-frequency noise in high-Tc superconducting thick films

International Nuclear Information System (INIS)

Aponte, J.M.; Gutierrez, G.; Octavio, M.

1990-01-01

In this paper experimental results on the resistance noise in thick films of YBa 2 Cu 3 O 7-δ in the vicinity of the superconducting transition are reported. The measurements were performed in samples with broad resistive transitions and in the frequency range from 1Hz to 100 Hz. The power spectral density S v /V 2 of the excess noise is obtained by subtracting the current-independent background noise from the total measured noise. The authors observed that at the transition, the magnitude of S v /V 2 rises above its level at room temperature exhibiting peaks at the same temperatures at which R -1 dR/dT has maxima. The authors performed measurements of S v /V 2 as a function of the current through the sample and the authors found that it diverges as the critical current is approached from above and that it is zero below the critical current. This transition is found to be described quite well by a percolation model
Optically activated high Tc superconducting microbolometer

International Nuclear Information System (INIS)

Yefremenko, V; Gordiyenko, E; Shustakova, G; Bader, S D; Karapetrov, G; Novosad, V

2006-01-01

A laser beam, precisely focused on the patterned superconducting structure, was used to nucleate a resistive area that is sensitive to external thermal effects. The electron beam lithography and wet chemical etching were applied as pattern transfer processes in epitaxial Y-Ba-Cu-O films. Two different sensor designs were tested: (i) 3 millimeters long and 40 micrometers wide stripe and (ii) 1.25 millimeters long, and 50 micron wide meander -like structure. It is shown experimentally that scanning the laser beam along the stripe leads to physical displacement of the sensitive area and, therefore may be used as a basis for imaging over a broad spectral range. For example, patterning the superconducting film into a meander structure is equivalent to a two-dimensional detector array. In additional to the simplicity of the detector fabrication sequence (one step mask transfer), a clear advantage of this approach is the simplicity of the read-out process: an image is formed by registering the signal with only two electrical terminals. The proposed approach can be extended for imaging over a wide spectral range
Superconductivity in Bi-Sr-Ca-Cu-O bulk and film ceramics

Energy Technology Data Exchange (ETDEWEB)

Sukhanov, A A; Ozmanian, KH R; Sandomirskii, B B

1988-07-01

A superconducting transition with Tc0 = 82-95 K and Tc(R = 0) = 82-72 K was observed in Bi(Sr/1-x/Ca/x/)2Cu3O(y) bulk and film specimens obtained via a solid-phase reaction. Temperature dependences of the resistance, critical current, and magnetic susceptibility were measured.
Growth of epitaxial Ba2YCu3O(7-delta) thin films and control of their superconducting properties

International Nuclear Information System (INIS)

Siegal, M.P.; Phillips, J.M.

1992-01-01

The relationship is experimentally defined between the superconducting behavior of Ba2YCu3O(7-delta) (BYCO) films and their structural characteristics. The BYCO films are grown on LaAlO3 100-plane by coevaporating BaF2, Y, and Cu followed by ex situ annealing, and the crystalline quality is tested by Rutherford backscattering ion channeling. SEM is employed to study film morphology, and several techniques are used to measure the transition temperature (Tc), critical current density (Jc), and the penetration length. It is found that point defects and dislocations decrease as the high-temperature stage (Ta) increases; crevices, pinholes, and microcracks are also noted which are related to specific values of Tc, Ta, and penetration length. The results of the present experiments indicate that the material properties of superconducting materials should be examined closely to distinguish between pure superconducting behavior and characteristics related to material structure. 21 refs
Influence of ion beam mixing on the growth of high temperature oxide superconducting thin film

International Nuclear Information System (INIS)

Bordes, N.; Rollett, A.D.; Cohen, M.R.; Nastasi, M.

1989-01-01

The superconducting properties of high temperature superconductor thin films are dependent on the quality of the substrate used to grow these films. In order to maximize the lattice matching between the superconducting film and the substrate, we have used a YBa 2 Cu 3 O 7 thin film deposited on left-angle 100 right-angle SrTiO 3 as a template. The first film was prepared by coevaporation of Y, BaF 2 and Cu on left-angle 100 right-angle SrTiO 3 , followed by an anneal in ''wet'' oxygen at 850 degree C. This film showed a sharp transition at about 90 K. A thicker layer of about 5000 A was then deposited on top of this first 2000 angstrom film, using the same procedure. After the post anneal at 850 degree C, the transition took place at 80 K and no epitaxy of the second film was observed. Ion beam mixing at 400 degree C, using 400 keV O ions was done at the interface of the two films (the second one being not annealed). After the post anneal, the film displayed an improved Tc at 90K. Moreover, epitaxy was shown to take place from the interface SrTiO 3 -123 film towards the surface and was dependent of the dose. These results will be discussed from the data obtained from Rutherford backscattering spectroscopy (RBS) combined with channeling experiments, x-ray diffraction (XRD) and scanning electron microscopy (SEM) observations. 8 refs., 2 figs., 2 tabs
High-Tc Superconducting Bolometer Noise Measurement Using Low Noise Transformers - Theory and Optimization

Science.gov (United States)

Aslam, Shahid; Jones, Hollis H.

2011-01-01

Care must always be taken when performing noise measurements on high-Tc superconducting materials to ensure that the results are not from the measurement system itself. One situation likely to occur is with low noise transformers. One of the least understood devices, it provides voltage gain for low impedance inputs (< 100 ), e.g., YBaCuO and GdBaCuO thin films, with comparatively lower noise levels than other devices for instance field effect and bipolar junction transistors. An essential point made in this paper is that because of the complex relationships between the transformer ports, input impedance variance alters the transformer s transfer function in particular, the low frequency cutoff shift. The transfer of external and intrinsic transformer noise to the output along with optimization and precautions are treated; all the while, we will cohesively connect the transfer function shift, the load impedance, and the actual noise at the transformer output.
Electronic structure and superconductivity of FeSe-related superconductors.

Science.gov (United States)

Liu, Xu; Zhao, Lin; He, Shaolong; He, Junfeng; Liu, Defa; Mou, Daixiang; Shen, Bing; Hu, Yong; Huang, Jianwei; Zhou, X J

2015-05-13

FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.
A study on the development of high Tc superconducting materials and on the effects of neutron irradiation

International Nuclear Information System (INIS)

Won, Dong Yeon; Chang, In Soon; Lee, Jong Min

1990-08-01

An Ag-sheathed (Pb,Bi)SrCaCuO superconducting tape was prepared by the cold rolling and post heat treatment method. The tape shows a c-oriented texture perpendicular to the rolling direction. The aligned grain structure may be resulted from the anisotropic grain growth of the high Tc superconducting phase. The bulk (Pb,Bi)SrCaCuO samples with (a) Tc=10lK and (b) 96K were prepared by the solid state reaction method and were neutron-irradiated up to 1.5 x 10 1 8 n/cm 2 . After irradiation the zero resistance temperature(Tc) of (a) was decreased to 96K but (b) did not show any change in Tc. The critical current density of (a) also decreased from 0.75A/cm 2 but (b) was constant as 1.5 A/cm 2 after irradiation. (Author)
Integrated-circuit microwave detector based on granular high-Tc thin films. [Y-Ba-Cu-O

Energy Technology Data Exchange (ETDEWEB)

Drobinin, A.V.; Lutovinov, V.S.; Starostenko, I.V. (Moscow Inst. of Radioengineering, Electronics and Automation, (MIREA), Moscow (USSR))

1991-12-01

A highly sensitive integrative-circuit microwave detector based on granular High-Tc film has been designed. All matching circuits and High-Tc microbridge are located on the same substrate. The voltage responsivity 10{sup 3} V/W has been found at 65 K and frequency 5 GHz. Different modes of microwave detection have been observed: bolometric response near Tc in high-quality films, rectification mode caused by an array of weak links dominating in low-quality films, detection caused by nonlinear magnetic flux motion. (orig.).
The stress-strain relationship for multilayers of the high Tc superconducting oxides

International Nuclear Information System (INIS)

Hidaka, H.; Yamamura, H.

1988-01-01

This paper reports the calculation of the stress-strain relationship for multilayers of the high Tc superconducting oxides. The elucidation of this relationship is expected quite helpful for the preparation of high-quality multilayers of these materials. This calculation is possible to do in the same way of Timoshenko's bi-metal treatment. The authors did computation of the residual stress and strain, and the state of stress and strain for these multilayers has been acquired in detail by this calculation
High temperature superconducting films by rf magnetron sputtering

International Nuclear Information System (INIS)

Kadin, A.M.; Ballentine, P.H.

1989-01-01

The authors have produced sputtered films of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O by rf magnetron sputtering from an oxide target consisting of loose reacted powder. The use of a large 8-inch stoichiometric target in the magnetron mode permits films located above the central region to be free of negative-ion resputtering effects, and hence yields reproducible, uniform stoichiometric compositions for a wide range of substrate temperatures. Superconducting YBCO films have been obtained either by sputtering at low temperatures followed by an 850 0 C oxygen anneal, or alternatively by depositing onto substrates heated to ∼600 - 650 0 C and cooling in oxygen. Films prepared by the former method on cubic zirconia substrate consist of randomly oriented crystallites with zero resistance above 83 K. Those deposited on zirconia at medium temperatures without the high-temperature anneal contain smooth partially oriented crystallites, with a slightly depressed T/sub c/ ∼75K. Finally, superconducting films have been deposited on MgO using a BiSrCaCu/sub 2/O/sub x/ powder target
Gauge Model of High-Tc Superconductivity

International Nuclear Information System (INIS)

Ng, Sze Kui

2012-01-01

A simple gauge model of superconductivity is presented. The seagull vertex term of this gauge model gives an attractive potential between electrons for the forming of Cooper pairs of superconductivity. This gauge model gives a unified description of superconductivity and magnetism including antiferromagnetism, pseudogap phenomenon, stripes phenomenon, paramagnetic Meissner effect, Type I and Type II supeconductivity and high-T c superconductivity. The doping mechanism of superconductivity is found. It is shown that the critical temperature T c is related to the ionization energies of elements and can be computed by a formula of T c . For the high-T c superconductors such as La 2-x Sr x CuO 4 , Y Ba 2 Cu 3 O 7 , and MgB 2 , the computational results of T c agree with the experimental results.
Superconducting Electronic Film Structures

Science.gov (United States)

1991-02-14

Segmuller, A., Cooper, E.I., Chisholm, M.F., Gupta, A. Shinde, S., and Laibowitz, R.B. Lanthanum gallate substrates for epitaxial high-T superconducting thin...M. F. Chisholm, A. Gupta, S. Shinde, and R. B. Laibowitz, " Lanthanum Gallate Substrates for Epitaxial High-T c Superconducting Thin Films," Appl...G. Forrester and J. Talvacchio, " Lanthanum Copper Oxide Buffer Layers for Growth of High-T c Superconductor Films," Disclosure No. RDS 90-065, filed
High-Tc film development for electronic applications

International Nuclear Information System (INIS)

Talvacchio, J.; Wagner, G.R.

1990-01-01

In this paper, the authors describe the requirements and status of high-T c superconductor (HTS) films for the development of electronic applications with an emphasis on passive microwave devices. One of the most general requirements, a low rf Surface resistance relative to Cu, has been achieved in films of several different HTS compounds. However the best films, made of YBa 2 Cu 3 O 7 (YBCO) by any one of several techniques, have in common a residual surface resistance that is much greater than predicted by conventional superconductivity theory. Improvement in films is also limited by the current size and selection of single-crystal substrate materials. Other issues that must be resolved to develop a full integrated circuit technology for HTS are substrate heating during film deposition, deposited epitaxial insulators, and determination of which interfaces in a multilevel circuit must be formed in situ

High temperature superconducting compounds II; Proceedings of the Second Symposium, Anaheim, CA, Feb. 20, 21, 1990

International Nuclear Information System (INIS)

Whang, S.H.; Dasgupta, A.; Laibowitz, R.

1990-01-01

Various topics relevant to the production and implementation of high-temperature superconducting compounds are highlighted including critical current; texturing; ceramics and novel processing; composites; deformation and consolidation; thin films; microstructures; tapes, filaments, and ribbons; and thermodynamics. The thermally activated flux creep, critical current density and current enhancement in high-temperature superconductors are addressed. Also discussed are the phase stability and microstructure of doped superconductors, mechanical considerations in the processing of high-Tc superconductors, fabrication and application of high current density, high RTc superconducting thin films and devices, the effect of substrate temperature and RF biasing on the composition of sputtered Bi-based superconducting thin films, and optical electron microanalysis of cuprate superconductors. The microstructure dependence of critical current density and fabrication of double-layered ribbons from cuprate are also discussed
New superconductors from granular to high T$_{c}$

CERN Document Server

Deutscher, Guy

2018-01-01

How new are the high Tc superconductors, as compared to the conventional low Tc ones? In what sense are these oxides different from regular metals in their normal state? How different is the mechanism for high Tc superconductivity from the well-known electron-phonon interaction that explains so well superconductivity in metals and alloys? What are the implications of the new features of the high Tc oxides for their practical applications? This interesting book aims to provide some answers to those questions, drawing particularly on similarities between the high Tc oxides and granular superconductors, which also present a short coherence length, a small superfluid density and an inhomogeneous structure.
New superconductors from granular to high T$_{c}$

CERN Document Server

Deutscher, Guy

2006-01-01

How new are the high Tc superconductors, as compared to the conventional low Tc ones? In what sense are these oxides different from regular metals in their normal state? How different is the mechanism for high Tc superconductivity from the well-known electron-phonon interaction that explains so well superconductivity in metals and alloys? What are the implications of the new features of the high Tc oxides for their practical applications? This book aims to give some answers to those questions, drawing particularly on similarities between the high Tc oxides and granular superconductors, which also present a maximum of their critical temperature near the metal-insulator transition.
Tc depression and superconductor-insulator transition in molybdenum nitride thin films

Science.gov (United States)

Ichikawa, F.; Makise, K.; Tsuneoka, T.; Maeda, S.; Shinozaki, B.

2018-03-01

We have studied that the Tc depression and the superconductor-insulator transition (SIT) in molybdenum nitride (MoN) thin films. Thin films were fabricated by reactive DC magnetron sputtering method onto (100) MgO substrates in the mixture of Ar and N2 gases. Several dozen MoN thin films were prepared in the range of 3 nm < thickness d < 60 nm. The resistance was measured by a DC four-probe technique. It is found that Tc decreases from 6.6 K for thick films with increase of the normal state sheet resistance {R}{{sq}}{{N}} and experimental data were fitted to the Finkel’stein formula using the bulk superconducting transition temperature Tc 0 = 6.45 K and the elastic scattering time of electron τ = 1.6 × 10‑16 s. From this analysis the critical sheet resistance Rc is found about 2 kΩ, which is smaller than the quantum sheet resistance R Q. This value of Rc is almost the same as those for 2D NbN films. The value of τ for MoN films is also the similar value for NbN films 1.0 × 10‑16 s, while Tc 0 is different from that for NbN films 14.85 K. It is indicated that the mechanism of SIT for MoN films is similar to that of NbN films, while the mean free path ℓ for MoN films is larger than that for NbN films.
The microscopic twins and their crystal phase in the high Tc Y-Ba-Cu-O and Dy-Ba-Cu-O superconductive ceramics

International Nuclear Information System (INIS)

Zu, Z.J.; Chen, Y.L.

1988-01-01

Most consider that the structure of Y-Ba- Cu-O and Dy-Ba-Cu-O stable superconductive crystals with high Tc is associated with the right-angled phase. The superconductivity is closely connected with the right-angled character of the crystalline texture; the better the right- angled character, the better the superconductivity. From statistical investigations of examples the authors have discovered that most of the Y-Ba-Cu-O and Dy-Ba-Cu-O superconductivity with high Tc ceramic crystals is in the monoclinic phase, which, consists of microscopic, lamellar, single twins. The long-columnar grains consisting of lamellar twin slabs show the optical characteristics of right-angled phase. The microscopic twinning and grain morphologies are summarized in this paper
Prediction of high-Tc conventional superconductivity in the ternary lithium borohydride system

Science.gov (United States)

Kokail, Christian; von der Linden, Wolfgang; Boeri, Lilia

2017-12-01

We investigate the superconducting ternary lithium borohydride phase diagram at pressures of 0 and 200 GPa using methods for evolutionary crystal structure prediction and linear-response calculations for the electron-phonon coupling. Our calculations show that the ground state phase at ambient pressure, LiBH4, stays in the P n m a space group and remains a wide band-gap insulator at all pressures investigated. Other phases along the 1 :1 :x Li:B:H line are also insulating. However, a full search of the ternary phase diagram at 200 GPa revealed a metallic Li2BH6 phase, which is thermodynamically stable down to 100 GPa. This superhydride phase, crystallizing in a F m 3 ¯m space group, is characterized by sixfold hydrogen-coordinated boron atoms occupying the fcc sites of the unit cell. Due to strong hydrogen-boron bonding this phase displays a critical temperature of ˜100 K between 100 and 200 GPa. Our investigations confirm that ternary compounds used in hydrogen-storage applications should exhibit high-Tc conventional superconductivity in diamond anvil cell experiments, and suggest a viable route to optimize the superconducting behavior of high-pressure hydrides, exploiting metallic covalent bonds.
Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

Science.gov (United States)

Bedekar, M. M.; Safari, A.; Wilber, W.

1992-11-01

Superconducting thin films of Bi-Sr-Ca-Cu-O have been deposited by KrF excimer laser ablation. The best in situ films showed a Tc onset of 110 K and a Tc(0) of 76 K. A study of the laser plume revealed the presence of two distinct regimes. The forward directed component increased with fluence and the film composition was stoichiometric in this region. This is in agreement with the results on the 123 system by Venkatesan et al. [1]. The film properties were found to be critically dependent on the substrate temperature and temperatures close to melting gave rise to 2212 and 2223 phases. At lower temperatures, 2201 and amorphous phases were obtained. The film morphology and superconducting properties were a function of the target to substrate distance and the oxygen pressure during deposition and cooling. An increase in the target to substrate distance led to a deterioration of the properties due to the energy consideration for the formation of 2212 and 2223 phases. The best films were obtained using cooling pressures of 700 Torr. The microwave surface resistance of the films measured at 35 GHz dropped below that of copper at 30 K. Film growth was studied using X-ray diffraction and STM/AFM. This work is a discussion of the role of the different variables on the film properties.
High-temperature superconductivity

International Nuclear Information System (INIS)

Lynn, J.W.

1990-01-01

This book discusses development in oxide materials with high superconducting transition temperature. Systems with Tc well above liquid nitrogen temperature are already a reality and higher Tc's are anticipated. The author discusses how the idea of a room-temperature superconductor appears to be a distinctly possible outcome of materials research
Strong correlations and the search for high-Tc superconductivity in chromium pnictides and chalcogenides

Science.gov (United States)

Pizarro, J. M.; Calderón, M. J.; Liu, J.; Muñoz, M. C.; Bascones, E.

2017-02-01

Undoped iron superconductors accommodate n =6 electrons in five d orbitals. Experimental and theoretical evidence shows that the strength of correlations increases with hole doping, as the electronic filling approaches half filling with n =5 electrons. This evidence delineates a scenario in which the parent compound of iron superconductors is the half-filled system, in analogy to cuprate superconductors. In cuprates the superconductivity can be induced upon electron or hole doping. In this work we propose to search for high-Tc superconductivity and strong correlations in chromium pnictides and chalcogenides with n slave-spin and multiorbital random-phase-approximation calculations we analyze the strength of the correlations and the superconducting and magnetic instabilities in these systems with the main focus on LaCrAsO. We find that electron-doped LaCrAsO is a strongly correlated system with competing magnetic interactions, with (π ,π ) antiferromagnetism and nodal d -wave pairing being the most plausible magnetic and superconducting instabilities, respectively.
Electrical Insulation of 500-m High-Tc Superconducting Power Cable

International Nuclear Information System (INIS)

Takahashi, T; Ichikawa, M; Suzuki, H; Okamoto, T; Akita, S; Mukoyama, S; Yagi, M; Maruyama, S; Kimura, A

2006-01-01

Electrical insulation is one of the essential technologies for the electric power apparatus. Determination of testing voltages and design method of the electrical insulation layer are inextricably linked each other, and are critical to developing and realizing a cold dielectric (CD) type high-Tc superconducting (HTS) power cable. The authors had proposed the electrical insulation design method with concepts of partial discharge-free designs for ac voltage condition. This paper discusses the testing voltages for a 77 kV 1000 A HTS power cable with a length of 500 m, and describes results of various voltage withstand test. As a result, it is concluded that the proposed electrical insulation design method is appropriate for the HTS power cable
Y1Ba2Cu3O(7-delta) thin film dc SQUIDs (superconducting quantum interference device)

Science.gov (United States)

Racah, Daniel

1991-03-01

Direct current superconducting quantum interferometers (SQUIDs) based on HTSC thin films have been measured and characterized. The thin films used were of different quality: (1) Granular films on Sapphire substrates, prepared either by e-gun evaporation, by laser ablation or by MOCVD (metal oxide chemical vapor deposition), (2) Epitaxial films on MgO substrates. Modulations of the voltage on the SQUIDs as a function of the applied flux have been observed in a wide range of temperatures. The nature of the modulation was found to be strongly dependent on the morphology of the film and on its critical current. The SQUIDs based on granular films were relatively noisy, hysteretic and with a complicated V-phi shape. Those devices based on low quality (lowIc) granular films could be measured only at low temperatures (much lower than 77 K). While those of higher quality (granular films with high Ic) could be measured near to the superconductive transition. The SQUID based on high quality epitaxial film was measured near Tc and showed an anomalous, time dependent behavior.
Internal resonance of an elastic body levitated above high-Tc superconducting bulks

International Nuclear Information System (INIS)

Kokuzawa, T; Toshihiko, S; Yoshizawa, M

2010-01-01

In high-Tc superconducting magnetic levitation systems, levitated bodies can keep stable levitation with no contact and no control and thus their damping is very small. Thanks to these features, their applications to various apparatus are expected. However, on account of their small damping, the nonlinearity of electromagnetic levitation force can give notable effects upon motion of the levitated bodies. Therefore this nonlinearity must be taken into account to accurately analyze the dynamical behavior of the levitated bodies. Structures of such a levitated body can show elastic deformation if the large electromagnetic force acts on it. Therefore, we need to deal with the model as an elastic body. As mentioned above, nonlinear characteristics easily appear in this elastic vibration on account of the small damping. Especially when the ratio of the natural frequencies of the eigenmodes is integer, internal resonance can occur. This nonlinear resonance is derived from nonlinear interactions among the eigenmodes of the elastic levitated body. This kind of internal resonance of an elastic body appearing in high-Tc superconducting levitation systems has not been studied so far. This research especially deals with internal resonance of a beam supported at both its ends by electromagnetic forces acting on permanent magnets. The governing equation with the nonlinear boundary conditions for the dynamics of a levitated beam has been derived. Numerical results show internal resonance of the 1st mode and the 3rd mode. Experimental results are qualitatively in good agreement with numerical ones.
Misfit dislocations and phase transformations in high-T sub c superconducting films

CERN Document Server

Gutkin, M Y

2002-01-01

A theoretical model is suggested that describes the effects of misfit stresses on defect structures, phase content and critical transition temperature T sub c in high-T sub c superconducting films. The focus is placed on the exemplary case of YBaCuO films deposited onto LaSrAlO sub 4 substrates. It is theoretically revealed here that misfit stresses are capable of inducing phase transformations controlled by the generation of misfit dislocations in growing cuprate films. These transformations, in the framework of the suggested model, account for experimental data on the influence of the film thickness on phase content and critical temperature T sub c of superconducting cuprate films, reported in the literature. The potential role of stress-assisted phase transformations in suppression of critical current density across grain boundaries in high-T sub c superconductors is briefly discussed.
Preparation of YBaCuO superconducting tape by RF magnetron sputtering

Energy Technology Data Exchange (ETDEWEB)

Fukutomi, Masao; Akutsu, Nakao; Tanaka, Yoshiaki; Asano, Toshihisa; Maeda, Hiroshi (National Research Inst. for Metals, Tsukuba (Japan); Mitsui Mining and Smelting Co., Ltd., Tokyo (Japan))

1989-04-01

The effect of buffer layers, conditions of film preparation, and the relation between superconducting characteristics and bombardment of high energy ions on films were discussed in an attempt to fabricate YBaCuO films on metallic substrates by sputtering. Hastelloy-X tapes and Chromel (Ni-10Cr) fine wires were used as metallic substrates, and MgO films as buffer layers, which were provided by sputtering a MgO sintered target and annealing. As a result, superconducting films were favorably obtained on the Hastelloy tapes with the MgO buffer layers, however, counter diffusion at the interface of the film and layer was unavoidable in annealing. C axis-highly oriented film with high zero resistance Tc was obtained in such an arrangement of the target and substrate as to lower the effect of 0{sup {minus}} ion resputtering, resulting in the most favorable Tc=80.4K. YBaCuO superconducting films could be also deposited on a bundle of Chromel fine wires preliminarily. 11 refs., 7 figs.
Contribution of nuclear microanalysis and of 18O tracer technique to study the oxygen sublattice in high Tc superconducting thin films

International Nuclear Information System (INIS)

Siejka, J.

1994-01-01

At first a short review of IBA contribution to the determination of composition and structure, including phonon properties of high T c superconducting oxides is presented. In the second part, IBA contribution to the elucidation of the mechanisms of thin film growth is presented. The emphasis is on the complementarity of IBA, Raman spectroscopy and XRD techniques to characterize thin films of high T c superconducting oxides. In the third part, some recent results related mainly to YBaCuO films grown on (100) oriented single crystalline bulk materials (MgO, LaAlO 3 , SrTiO 3 ) is discussed. In these experiments, IBA, XRD and Raman spectroscopies were used to study the oxygen content in a series of YBaCuO films prepared in different conditions of pressure and temperature. In the case of c-axis oriented films a good agreement between these three methods was found for the films cooled down at high oxygen pressure and a significant disagreement for the films cooled down at low oxygen pressure, showing structures with anomalous c-axis parameter. In the case of a-axis oriented films grown on SrTiO 3 substrates it was found that the low T c values (∼ 70-80 K) are not correlated with the oxygen content but rather with a disorder in the oxygen sublattice. The disorder in the oxygen sublattice was studied using the 16 O(α, α) 16 O resonance in random and channeling geometry. These results are correlated with the data provided by Raman spectroscopy. The 18 O tracer technique was used to estimate the diffusion coefficient in the a-axis oriented YBaCuO films showing a huge anisotropy of the 18 O labelling. Combining Raman and IBA techniques, the selective 18 O labelling of the CuO chain-planes was evidenced. The defects in the 18 O enriched CuO chain-planes were studied using the 18 O(p, α) 15 N nuclear resonant reaction in random and channeling geometries. Some preliminary results related to roughness of YBaCuO films are also discussed. The physical implications of these
High-Tc cuprate superconductivity in a nutshell

International Nuclear Information System (INIS)

Won, Hyekyung; Haas, Stephan; Parker, David; Maki, Kazumi

2005-01-01

Since the discovery of high-T c cuprate superconductivity in 1986 many new experimental techniques and theoretical concepts have been developed. In particular it was shown that the BCS theory of d-wave superconductivity describes semi-quantitatively the high-T c superconductivity. Furthermore, it was demonstrated that Volovik's approach is extremely useful for finding the quasiparticle properties in the vortex state. Here we survey these developments and forecast future directions. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
High Tc superconducting magnetic multivibrators for fluxgate magnetic-field sensors

International Nuclear Information System (INIS)

Mohri, K.; Uchiyama, T.; Ozeki, A.

1989-01-01

Sensitive and quick-response nonlinear inductance characteristics are found for high Tc superconducting (YBa 2 Cu 3 O 7-chi ) disk cores at 77K in which soft magnetic BH hysteresis loops are observed. Various quick response magnetic devices such as modulators, amplifiers and sensors are built using these cores. The magnetizing frequency can be set to more than 20 MHz, which is difficult for conventional ferromagnetic bulk materials such as Permalloy amorphous alloys and ferrite. New quick-response fluxgate type magnetic-field sensors are made using ac and dc voltage sources. The former is used for second-harmonic type sensors, while the latter is for voltage-output multivibrator type sensors. Stable and quick-response sensor characteristics were obtained for two-core type multivibrators
Design and Characteristics Analysis of a Rod Type High-Tc Superconducting Fault Current Limiter through Electromagnetic Analysis

Energy Technology Data Exchange (ETDEWEB)

Hyun, O.B. [Korea Electric Power Research Institute, Taejeon (Korea); Lee, C.J.; Lee, S.J.; Ko, T.K. [Yonsei University, Seoul (Korea)

2001-07-01

The existence of a large air gaps between a High-Tc Superconducting (HTS) tube and an iron core, or between a primary winding and a HTS tube possibly causes magnetic flux leaks, resulting in undesirable voltage drops under normal operation. For this reason optimization of air gaps is essential in designing a high-Tc superconducting fault current limiter (SFCL). In this paper we performed the electromagnetic analysis for the optimization. The inductance L decreases by 20% as the hight of the winding increases from 50 to 200 mm. But, L increases from 5.6 mH to 10.5 mH as the hight of the rod changes from 150 to 400 mm. L is found to be almost constant for the air gap between 5 to 10 mm, but L decreases by 20% as the gap increases from 10 to 20 mm. The computational and experimental results will bo compared. (author). 7 refs., 8 figs., 1 tab.
Lanthanum gallate substrates for epitaxial high-temperature superconducting thin films

Science.gov (United States)

Sandstrom, R. L.; Giess, E. A.; Gallagher, W. J.; Segmuller, A.; Cooper, E. I.

1988-11-01

It is demonstrated that lanthanum gallate (LaGaO3) has considerable potential as an electronic substrate material for high-temperature superconducting films. It provides a good lattice and thermal expansion match to YBa2Cu3O(7-x), can be grown in large crystal sizes, is compatible with high-temperature film processing, and has a reasonably low dielectric constant and low dielectric losses. Epitaxial YBa2Cu3O(7-x) films grown on LaGaO3 single-crystal substrates by three techniques have zero resistance between 87 and 91 K.
Characterization of superconducting thin films by infrared reflection

International Nuclear Information System (INIS)

Gervais, F.

1988-01-01

Infrared reflectivity spectroscopy is shown to be a powerful tool to characterize the new high-Tc oxide superconductors since it gives information about the superconducting gap, phonons, plasmon and possibly low-energy electronic excitations such as excitons, information relevant to understand the mechanism of superconductivity [fr

Simple method for resistance measurements on thin films and bulk of high T_c superconducting materials

Science.gov (United States)

Alzetta, G.; Arimondo, E.; Celli, R. M.; Fuso, F.

1994-08-01

Two experimental techniques for measuring resistivity behaviour of high T_c ceramic superconductors in bulk or thin films are described. Particular attention has been given to the development of a four point contact system, easy to use for reliable resistance measurements under repeated, wide thermal cycles. On expose deux méthodes de mesure de la résistivité des supraconducteurs HTc en forme de couches minces déposées sur un substrat ou des céramiques frittées. Le dispositif de mesure, qui a été réalisé avec quatre contacts élastiques, permet d'obtenir des résultats reproductibles dans de très larges intervalles de température.
Preparation of high quality superconducting thin MgB2 films for electronics

International Nuclear Information System (INIS)

Surdu, Andrei; Zdravkov, Vladimir; Sidorenko, Anatolie; Rossolenko, Anna; Ryazanov, Valerii; Bdikin, Igor; Kroemer, Oliver; Nold, Eberhard; Koch, Thomas; Schimmel, Thomas

2007-01-01

In this work we report the growth of high-Tc MgB 2 smooth films which are prepared in a two-step process: 1) deposition of the precursor films and 2) their annealing in Mg vapor with a specially designed, reusable reactor. Our method opens perspectives for the use of MgB 2 films in microelectronics, especially for high-frequency applications. (authors)
Introduction to superconductivity and high-Tc materials

International Nuclear Information System (INIS)

Cyrot, M.; Pavuna, D.

1991-01-01

What sets this book apart from other introductions to superconductivity and high-T c materials is its pragmatic approach. In this book the authors describe all relevant superconducting phenomena and rely on the macroscopic Ginzburg-Landau theory to derive the most important results. Examples are chosen from selected conventional superconductors like NbTi and compared to those high-T c materials. The text should be of interest to non-specialists in superconductivity either as a textbook for those entering the field (one semester course) or as researchers in advanced technologies and even some managers of interdisciplinary research projects
Lanthanide gallate perovskite-type substrates for epitaxial, high-Tc superconducting Ba2YCu3O7-δ films

International Nuclear Information System (INIS)

Giess, E.A.; Sandstrom, R.L.; Gallagher, W.J.; Gupta, A.; Shinde, S.L.; Cook, R.F.; Cooper, E.L.; O'Sullivan, E.M.J.; Roldan, J.M.; Segmuller, A.D.; Angilello, J.

1990-01-01

This paper reports on the use of lanthanide gallate perovskite-type substrates for the deposition of epitaxial, high-T c superconducting Ba 2 YCu 3 O 7-δ (BYCO) films. They were also found to have moderate dielectric constants (∼25 compared to ∼ 277 for SrTiO 3 ). This study was undertaken to further explore the use of LaGaO 3 , NdGaO 3 , SrTiO 3 , MgO, and Y-stabilized ZrO 2 substrates, prepared from single-crystal joules grown by several suppliers using the Czochralski method. Films were prepared by cylindrical magnetron sputtering and laser ablation. Substrate evaluations included measurement of dielectric constant and loss, thermal expansion, and mechanical hardness and toughness. In addition to their moderate dielectric constants, they were found to have satisfactory mechanical properties, except for the twinning tendency of LaGaO 3 . Lattice mismatch strains were calculated for orthorhombic BYCO films on a number of substrates. NdGaO 3 was found to have the best lattice match with BYCO, and is now available twin-free
Rugged Low-Resistance Contacts To High-Tc Superconductors

Science.gov (United States)

Caton, Randall; Selim, Raouf; Byvik, Charles E.; Buoncristiani, A. Martin

1992-01-01

Newly developed technique involving use of gold makes possible to fabricate low-resistance contacts with rugged connections to high-Tc superconductors. Gold diffused into specimen of superconducting material by melting gold beads onto surface of specimen, making strong mechanical contacts. Shear strength of gold bead contacts greater than epoxy or silver paste. Practical use in high-current-carrying applications of new high-Tc materials, including superconducting magnets, long-wavelength sensors, electrical ground planes at low temperatures, and efficient transmission of power.
Electrochemistry of high-tc superconductors

International Nuclear Information System (INIS)

Petrij, O.A.; Tsirlina, G.A.

1993-01-01

The review deals with the problems of formation of a new section in modern electrochemistry related to various electrochemical aspects of high-temperature superconductivity. Specific properties of multicomponent oxides as electrode materials are pointed out. The data of experimental works on the study of degradation of superconducting ceramics, electroanalysis of complex oxide systems, electric deposition of metals and polymer films upon them are described. Special attention is paid to electrochemical approaches to electrosynthesis of films, possessing high-temperature superconductivity
Thin film production of ceramic high-Tc-superconductors (targets)

International Nuclear Information System (INIS)

1992-01-01

Presently high-quality thin superconducting films having high T c 's may prepared by the sputtering technique. However, a large-area coating is required for an industrial application. One requirement is the availability of sputter targets with controlled and reproducible properties. By means of basic experiments with respect to powder processing, shaping and the densification process superconducting targets up to 200 mm in diameter were prepared in the Y-Ba-Cu-O- system. Additionally, targets from other systems with different geometries (e.g. ring targets) were prepared. These targets were submitted to the project partners as well as to other institutes and companies. During the course of this project the foundations for an industrial-type coating of large-area substrates were elaborated. (orig.). 9 refs., 5 tabs., 15 figs [de
Lanthanum gallate substrates for epitaxial high-temperature superconducting thin films

International Nuclear Information System (INIS)

Sandstrom, R.L.; Giess, E.A.; Gallagher, W.J.; Segmueller, A.; Cooper, E.I.; Chisholm, M.F.; Gupta, A.; Shinde, S.; Laibowitz, R.B.

1988-01-01

We demonstrate that lanthanum gallate (LaGaO 3 ) has considerable potential as an electronic substrate material for high-temperature superconducting films. It provides a good lattice and thermal expansion match to YBa 2 Cu 3 O/sub 7-//sub x/, can be grown in large crystal sizes, is compatible with high-temperature film processing, and has a reasonably low dielectric constant (ε≅25) and low dielectric losses. Epitaxial YBa 2 Cu 3 O/sub 7-//sub x/ films grown on LaGaO 3 single-crystal substrates by three techniques have zero resistance between 87 and 91 K
Effects of high-energy proton irradiation on the superconducting properties of Fe(Se,Te) thin films

Science.gov (United States)

Sylva, G.; Bellingeri, E.; Ferdeghini, C.; Martinelli, A.; Pallecchi, I.; Pellegrino, L.; Putti, M.; Ghigo, G.; Gozzelino, L.; Torsello, D.; Grimaldi, G.; Leo, A.; Nigro, A.; Braccini, V.

2018-05-01

In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out an experimental investigation with different irradiation fluences up to 7.30 · 1016 cm‑2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enhanced or suppressed, what are the effects of irradiation on the critical temperature, resistivity, and critical magnetic fields, and finally what is the role played by the substrate in this context. We find that the effect of irradiation on superconducting properties is generally small compared to the case of other iron-based superconductors. The irradiation effect is more evident on the critical current density Jc, while it is minor on the transition temperature Tc, normal state resistivity ρ, and on the upper critical field Hc2 up to the highest fluences explored in this work. In more detail, our analysis shows that when protons implant in the substrate far from the superconducting film, the critical current can be enhanced up to 50% of the pristine value at 7 T and 12 K; meanwhile, there is no appreciable effect on critical temperature and critical fields together with a slight decrease in resistivity. On the contrary, when the implantation layer is closer to the film–substrate interface, both critical current and temperature show a decrease accompanied by an enhancement of the resistivity and lattice strain. This result evidences that possible modifications induced by irradiation in the substrate may affect the superconducting properties of the film via lattice strain. The robustness of the Fe(Se,Te) system to irradiation-induced damage makes it a promising compound for the fabrication of magnets in high-energy accelerators.
Thermal propagation and stability in superconducting films

International Nuclear Information System (INIS)

Gray, K.E.; Kampwirth, R.T.; Zasadzinski, J.F.; Ducharme, S.P.

1983-01-01

Thermal propagation and stable hot spots (normal domains) are studied in various high Tsub(c) superconducting films (Nb 3 Sn, Nb, NbN and Nb 3 Ge). A new energy balance is shown to give reasonable quantitative agreement of the dependence of the propagation velocity on the length of short normal domains. The steady state (zero velocity) measurements indicate the existence of two distinct situations for films on high thermal conductivity (sapphire) substrates. For low power per unit area the film and substrate have the same temperature, and the thermal properties of the substrate dominate. However, for higher power densities in short hot spots, the coupling is relatively weak and the thermal properties of the film alone are important. Here a connection is made between the critical current stability of superconducting films and a critical hot spot size for thermal propagation. As a result efficient heat removal is shown to dominate the stabilisation of superconducting films. The strong and weak coupling situations also lead to modifications of the models for propagation velocities on sapphire substrates. Self-healing of hot spots and other phenomena in superconducting film are explained. The potential use of the thermal propagation model in applications of superconductors, especially switches is discussed. (author)
High-frequency properties of superconducting Y-Ba-Cu-oxide thin films

International Nuclear Information System (INIS)

Ramakrishnan, E.S.; Su, M.; Howng, W.

1992-01-01

rf and microwave properties of superconducting YBa 2 Cu 3 O 7-x thin films were measured and analyzed using a coplanar resonator structure. The films were developed by sequential electron-beam evaporation of the metals followed by postanneal processing. dc properties of the films were obtained from resistance-temperature and current-voltage measurements to evaluate the transition temperature and current densities. High-frequency properties were measured from 70 to 10 K and in the frequency range 1--3 GHz to determine the film characteristics as compared to pure copper films on the same substrates
Femtosecond optical detection of quasiparticle dynamics in high-Tc YBa2Cu3O7-δ superconducting thin films

International Nuclear Information System (INIS)

Han, S.G.; Vardeny, Z.V.; Wong, K.S.; Symko, O.G.; Koren, G.

1990-01-01

Femtosecond dynamics of photogenerated quasiparticles in YBa 2 Cu 3 O 7-δ superconducting thin films shows, at T≤T c , two main electronic processes: (i) quasiparticle avalanche production during hot-carrier thermalization, which takes about 300 fsec; (ii) recombination of quasiparticles to form Cooper pairs, which is completed within 5 psec. In contrastr, nonsuperconducting epitaxial films such as PrBa 2 Cu 2 O 7 and YBa 2 Cu 3 O 6 show regular picosecond electronic response
Quality criteria for high Tc superconductors and on the clarification of the superconducting mechanism

International Nuclear Information System (INIS)

Haase, E.L.; Ruzicka, J.

1992-03-01

After the successful basic solution of the Nb 3 Ge and Nb 3 Si problems, optimization strategies and quality criteria were developed for high Tc superconducting (HTCS) samples in analogy. After improvements of the sputtering system, the preparation parameters were tightly controlled, leading to samples with a reproducible linear slope of the specific resistance ρ(T). Further improvements by us and Poppe et al. lead to the preparation of 123 films with non-linear ρ(T) curves above 120K. A generalization to a T 2 behavior of ρ(T) leads to the further generalization that defect free HTCS are essentially two dimensional in nature, with all ensuing consequences. The momentum transport of the moving charge cariers requires, because of momentum conservation, a mechanism to transfer momentum to the lattice (momentum relaxation). The qualitative theory developed for two dimensional (2D) systems shows that the electron-phonon interaction is strongly suppressed and hence that the weaker electron-electron interaction dominates. That theory makes numerous predictions, which so far are confirmed by experiments. In particular, it accounts for the extreme temperature dependence of the mean free path and the Hall effect. It is inferred that the mechanism of HTCS is predominantly due to electron-electron interaction - probably of bipolaron nature, as indicated by experiment. At this point experiment meets just a few theories, that conform with the experimental facts and above theory, all based on the quasi-particle theory of electron-electron interaction. The theory of Newns, Pattnaik and Tsuei should have a T 2 shape of ρ(T) and, because E F lies near a nearly logarithmic van Hove singularity, accounts for the high Tc. Ruvalds and Virosztek's theory predicts the T 2 shape of ρ(T). (orig./GSCH)
High-Tc superconductor applications

International Nuclear Information System (INIS)

Anon.

1988-01-01

There has been much speculation about new products and business opportunities which high-Tc superconductors might make possible. However, with the exception of one Japanese survey, there have not been any recognized forecasts suggesting a timeframe and relative economic impact for proposed high-Tc products. The purpose of this survey is to provide definitive projections of the timetable for high-Tc product development, based on the combined forecasts of the leading U.S. superconductivity experts. The FTS panel of experts on high-Tc superconductor applications, representing both business and research, forecast the commercialization and economic impact for 28 classes of electronic, magnetic, communications, instrumentation, transportation, industrial, and power generation products. In most cases, forecasts predict the occurrence of developments within a 90% statistical confidence limit of 2-to-3 years. The report provides background information on the 28 application areas, as well as other information useful for strategic planners. The panel also forecast high-Tc research spending, markets, and international competitiveness, and provide insight into how the industry will evolve
Final report: High current capacity high temperature superconducting film based tape for high field magnets

International Nuclear Information System (INIS)

Ying Xin

2000-01-01

The primary goal of the program was to establish the process parameters for the continuous deposition of high quality, superconducting YBCO films on one meter lengths of buffered RABiTS tape using MOCVD and to characterize the potential utility of the resulting tapes in high field magnet applications
Colloquium: High pressure and road to room temperature superconductivity

Science.gov (United States)

Gor'kov, Lev P.; Kresin, Vladimir Z.

2018-01-01

This Colloquium is concerned with the superconducting state of new high-Tc compounds containing hydrogen ions (hydrides). Recently superconductivity with the record-setting transition temperature of Tc=203 K was reported for sulfur hydrides under high pressure. In general, high pressure serves as a path finding tool toward novel structures, including those with very high Tc . The field has a rich and interesting history. Currently, it is broadly recognized that superconductivity in sulfur hydrides owes its origin to the phonon mechanism. However, the picture differs from the conventional one in important ways. The phonon spectrum in sulfur hydride is both broad and has a complex structure. Superconductivity arises mainly due to strong coupling to the high-frequency optical modes, although the acoustic phonons also make a noticeable contribution. A new approach is described, which generalizes the standard treatment of the phonon mechanism and makes it possible to obtain an analytical expression for Tc in this phase. It turns out that, unlike in the conventional case, the value of the isotope coefficient (for the deuterium-hydrogen substitution) varies with the pressure and reflects the impact of the optical modes. The phase diagram, that is the pressure dependence of Tc , is rather peculiar. A crucial feature is that increasing pressure results in a series of structural transitions, including the one which yields the superconducting phase with the record Tc of 203 K. In a narrow region near P ≈150 GPa the critical temperature rises sharply from Tc≈120 to ≈200 K . It seems that the sharp structural transition, which produces the high-Tc phase, is a first-order phase transition caused by interaction between the order parameter and lattice deformations. A remarkable feature of the electronic spectrum in the high-Tc phase is the appearance of small pockets at the Fermi level. Their presence leads to a two-gap spectrum, which can, in principle, be observed with the
Growth of high Tc Bi-Sr-Ca-Cu-O thick films

International Nuclear Information System (INIS)

Chaudhry, Sangeeta; Khare, Neeraj; Gupta, A.K.; Nagpal, K.C.; Ojha, V.N.; Reddy, G.S.N.; Tomar, V.S.

1991-01-01

Thick films of Bi-Sr-Ca-Cu-O were deposited on (100) MgO substrates by screen-printing technique with the starting composition 1112. To attain the superconducting state, the films were subjected to two-step heat-treatment. R-T and XRD have been studied for films annealed at different durations of the second step. Initially T c (R=O) increased from 77 to 103 K as the annealing duration was increased after which T c decreased. Kinetics of the growth of high T c phase is discussed in the light of results. (author). 7 refs., 2 figs., 1 tab
An effective 2-band eg model of sulfur hydride H3S for high-Tc superconductivity

Science.gov (United States)

Nishiguchi, Kazutaka; Teranishi, Shingo; Miyao, Satoaki; Matsushita, Goh; Kusakabe, Koichi

To understand high transition temperature (Tc) superconductivity in sulfur hydride H3S, we propose an effective 2-band model having the eg symmetry as the minimal model for H3S. Two eg orbitals centered on a sulfur S atom are chosen for the smallest representation of relevant bands with the van-Hove singularity around the Fermi levels except for the Γ-centered small hole pockets by the sulfur 3 p orbitals. By using the maximally localized Wannier functions, we derive the minimal effective model preserving the body-centered cubic (bcc) crystal symmetry of the H3S phase having the highest Tc ( 203 K under pressures) among the other polymorphs of H3S.
Direct Observation of High-Temperature Superconductivity in One-Unit-Cell FeSe Films

International Nuclear Information System (INIS)

Zhang Wen-Hao; Zhang Jin-Song; Li Fang-Sen; Guo Ming-Hua; Ding Hao; Tang Chen-Jia; Wang Qing-Yan; He Ke; Ji Shuai-Hua; Chen Xi; Sun Yi; Zhao Yan-Fei; Xing Ying; Wang Hui-Chao; Zhang Hui-Min; Peng Jun-Ping; Li Zhi; Wang Meng; Fujita Takeshi; Hirata Akihiko

2014-01-01

We prepared one-unit-cell (1-UC) thick FeSe films on insulating SrTiO 3 substrates with non-superconducting FeTe protection layers by molecular beam epitaxy for ex situ studies. By direct transport and magnetic measurements, we provide definitive evidence for high temperature superconductivity in the 1-UC FeSe films with an onset T C above 40 K and an extremely large critical current density J C ∼1.7×10 6 A/cm 2 at 2 K, which are much higher than T C ∼8 K and J C ∼10 4 A/cm 2 for bulk FeSe, respectively. Our work may pave the way to enhancing and tailoring superconductivity by interface engineering. (express letter)
Superconductivity applications for infrared and microwave devices II; Proceedings of the Meeting, Orlando, FL, Apr. 4, 5, 1991

Science.gov (United States)

Heinen, Vernon O.; Bhasin, Kul B.

Topics discussed include thin-film technology, microwave transmission lines and resonators, microwave devices and circuits, infrared detectors and bolometers, and superconducting junctions. Papers are presented on possible enhancement in bolometric response using free-standing film of YBa2Cu3O(x), aging and surface instability in high-Tc superconductors, epitaxial Tl2Ba2CaCu2O8 thin films on LaAlO3 and their microwave device properties, the performance of stripline resonators using sputtered YBCO films, and a coplanar waveguide microwave filter of YBa2Cu3O7. Attention is also given to the performance characteristics of Y-Ba-Cu-O microwave superconducting detectors, high-Tc bolometer developments for planetary missions, infrared detectors from YBaCuO thin films, high-temperature superconductor junction technology, and submillimeter receiver components using superconducting tunnel junctions. (For individual items see A93-27244 to A93-27248)

Variable temperature superconducting microscope

Science.gov (United States)

Cheng, Bo; Yeh, W. J.

2000-03-01

We have developed and tested a promising type of superconducting quantum interference device (SQUID) microscope, which can be used to detect vortex motion and can operate in magnetic fields over a large temperature range. The system utilizes a single-loop coupling transformer, consisting of a patterned high Tc superconducting thin film. At one end of the transformer, a 20 μm diam detecting loop is placed close to the sample. At the other end, a large loop is coupled to a NbTi coil, which is connected to a low Tc SQUID sensor. Transformers in a variety of sizes have been tested and calibrated. The results show that the system is capable of detecting the motion of a single vortex. We have used the microscope to study the behavior of moving vortices at various positions in a YBa2Cu3O7 thin film bridge.
Depth profiling of superconducting thin films using rare gas ion sputtering with laser postionization

Science.gov (United States)

Pallix, J. B.; Becker, C. H.; Missert, N.; Char, K.; Hammond, R. H.

1988-02-01

Surface analysis by laser ionization (SALI) has been used to examine a high-Tc superconducting thin film of nominal composition YBa2Cu3O7 deposited on SrTiO3 (100) by reactive magnetron sputtering. The main focus of this work was to probe the compositional uniformity and the impurity content throughout the 1800 Å thick film having critical current densities of 1 to 2×106 A/cm2. SALI depth profiles show this film to be more uniform than thicker films (˜1 μm, prepared by electron beam codeposition) which were studied previously, yet the data show that some additional (non-superconducting) phases derived from Y, Ba, Cu, and O are still present. These additional phases are studied by monitoring the atomic and diatomic-oxide photoion profiles and also the depth profiles of various clusters (e.g. Y2O2+, Y2O3+, Y3O4+, Ba2O+, Ba2O2+, BaCu+, BaCuO+, YBaO2+, YSrO2+, etc.). A variety of impurities are observed to occur throughout the film including rather large concentrations of Sr. Hydroxides, F, Cl, and COx are evident particularly in the sample's near surface region (the top ˜100 Å).
Microwave superconductivity for particle accelerators - How the high TC superconductors measure up

International Nuclear Information System (INIS)

Padamsee, H.; Green, K.; Gruschus, J.

1988-01-01

Application of superconducting niobium cavities to accelerators for high energy physics, nuclear physics and free electron laser is growing rapidly. Cornell has a long standing effort in the development of superconducting RF accelerator technology. Nb cavities developed here from the basis for constructing the world's highest energy electron accelerator for nuclear physics. These cavities have set a standard against which the behavior of the new superconductors must be compared. From available results on dc critical fields, and the energy gap, it appears that the new materials could make a significant impact on the capabilities of future accelerators. Crucial to this assessment, however, are direct microwave loss measurements, together with measurements of the energy gap and RF frequency dependence as well as the behavior at high RF fields. Latest results on these properties for bulk sintered ceramics, thin films and single crystals at RF frequencies of 1.5 and 6 Ghz are presented
Bi-Polaron Condensation in High Tc Superconductors

International Nuclear Information System (INIS)

Ranninger, J.

1995-01-01

On the basis of optical measurements-, photoemission-, EXAFS- and neutron scattering-experiments we conclude that itinerant valence electrons coexist with localized bi-polarons.Entering the metallic phase upon chemical doping, a charge transfer between the two electronic subsystems is triggered off. We show that as the temperature is lowered towards Tc this process leads to a delocalization of bi-polarons due to a precursor effect of superfluidity of those bi-polarons. Upon entering the superconducting phase, these bipolarons ultimately condense into a superfluid state which is expected to largely determine the superconducting properties of high Tc materials. (authors)
Structure and superconducting properties of Nb-Zr alloy films made by a high-rate sputtering

International Nuclear Information System (INIS)

Sekine, Hisashi; Inoue, Kiyoshi; Tachikawa, Kyoji

1978-01-01

Superconducting Nb-Zr alloy films have been prepared by a continuous high-rate sputtering on tantalum substrates. A deposition rate of 330 nm/min has been attained. The compositional profile in the Nb-Zr film is quite uniform and the film has nearly the same composition as that of the target. The films deposited in a pure argon atmosphere show a columnar structure grown perpendicular to the substrate. The grain size strongly depends on the substrate temperature. The phase transformations in the Nb-Zr film become more apparent and the structure becomes closer to the equilibrium state as the film is deposited in higher atmosphere pressures and/or at lower target voltages. The superconducting transition temperature T sub(c) of the films is about the same as that of bulk samples. The dependence of T sub(c) on the substrate temperature is explainable on the phase transformations in the film. Critical current density J sub(c) and its anisotropy is closely related to the grain structure of the film. Grain boundaries seem to act as the most predominant flux pinning centers in the films. Effects of oxygen in the sputtering atmosphere on the structure and superconducting properties of the Nb-Zr films have been also investigated. Oxygen significantly decreases the grain size of the film. Oxygen increases J sub(c) but decreases T sub(c) of the film. (auth.)
Superconductivity of high Tc Scientific revolution?

International Nuclear Information System (INIS)

Marquina, J.E.; Ridaura, R.; Gomez, R.; Marquina, V.; Alvarez, J.L.

1997-01-01

A short history of superconductivity, since its discovery by Bednorz and Muller to the development of new materials with high transition temperatures, is presented. Further evolvements are analyzed in terms of T.s. Kuhn conceptions expressed in his book. The Structure of Scientific Revolutions. (Author) 4 refs
Spectroscopy of metal "superatom" nanoclusters and high-Tc superconducting pairing

Science.gov (United States)

Halder, Avik; Kresin, Vitaly V.

2015-12-01

A unique property of metal nanoclusters is the "superatom" shell structure of their delocalized electrons. The electronic shell levels are highly degenerate and therefore represent sharp peaks in the density of states. This can enable exceptionally strong electron pairing in certain clusters composed of tens to hundreds of atoms. In a finite system, such as a free nanocluster or a nucleus, pairing is observed most clearly via its effect on the energy spectrum of the constituent fermions. Accordingly, we performed a photoionization spectroscopy study of size-resolved aluminum nanoclusters and observed a rapid rise in the near-threshold density of states of several clusters (A l37 ,44 ,66 ,68 ) with decreasing temperature. The characteristics of this behavior are consistent with compression of the density of states by a pairing transition into a high-temperature superconducting state with Tc≳100 K. This value exceeds that of bulk aluminum by two orders of magnitude. These results highlight the potential of novel pairing effects in size-quantized systems and the possibility to attain even higher critical temperatures by optimizing the particles' size and composition. As a new class of high-temperature superconductors, such metal nanocluster particles are promising building blocks for high-Tc materials, devices, and networks.
Temperature Dependence of Quasiparticle Spectral Weight and Coherence in High Tc Superconductors

Science.gov (United States)

He, Yang; Zhang, Jessie; Hoffman, Jennifer; Hoffman Lab Team

2014-03-01

Superconductivity arises from the Cooper pairing of quasiparticles on the Fermi surface. Understanding the formation of Cooper pairs is an essential step towards unveiling the mechanism of high Tc superconductivity. We compare scanning tunneling microscope investigations of the temperature dependence of quasiparticle spectral weight and quasiparticle interference in several families of high Tc materials. We calculate the coherent spectral weight related to superconductivity, despite the coexistence of competing orders. The relation between pairing temperature and coherent spectral weight is discussed. We acknowledge support by the New York Community Trust-George Merck Fund.
Finding new superconductors: the spin-fluctuation gateway to high Tc and possible room temperature superconductivity.

Science.gov (United States)

Pines, David

2013-10-24

We propose an experiment-based strategy for finding new high transition temperature superconductors that is based on the well-established spin fluctuation magnetic gateway to superconductivity in which the attractive quasiparticle interaction needed for superconductivity comes from their coupling to dynamical spin fluctuations originating in the proximity of the material to an antiferromagnetic state. We show how lessons learned by combining the results of almost three decades of intensive experimental and theoretical study of the cuprates with those found in the decade-long study of a strikingly similar family of unconventional heavy electron superconductors, the 115 materials, can prove helpful in carrying out that search. We conclude that, since Tc in these materials scales approximately with the strength of the interaction, J, between the nearest neighbor local moments in their parent antiferromagnetic state, there may not be a magnetic ceiling that would prevent one from discovering a room temperature superconductor.
Modal bifurcation in a high-Tc superconducting levitation system

International Nuclear Information System (INIS)

Taguchi, D; Fujiwara, S; Sugiura, T

2011-01-01

This paper deals with modal bifurcation of a multi-degree-of-freedom high-T c superconducting levitation system. As modeling of large-scale high-T c superconducting levitation applications, where plural superconducting bulks are often used, it can be helpful to consider a system constituting of multiple oscillators magnetically coupled with each other. This paper investigates nonlinear dynamics of two permanent magnets levitated above high-T c superconducting bulks and placed between two fixed permanent magnets without contact. First, the nonlinear equations of motion of the levitated magnets were derived. Then the method of averaging was applied to them. It can be found from the obtained solutions that this nonlinear two degree-of-freedom system can have two asymmetric modes, in addition to a symmetric mode and an antisymmetric mode both of which also exist in the linearized system. One of the backbone curves in the frequency response shows a modal bifurcation where the two stable asymmetric modes mentioned above appear with destabilization of the antisymmetric mode, thus leading to modal localization. These analytical predictions have been confirmed in our numerical analysis and experiments of free vibration and forced vibration. These results, never predicted by linear analysis, can be important for application of high-T c superconducting levitation systems.
Laser patterning of superconducting oxide films

International Nuclear Information System (INIS)

Gupta, A.; Hussey, B.W.; Koren, G.; Cooper, E.I.; Jagannathan, R.

1988-01-01

The focused output of an argon ion laser (514.5 nm) has been used for wiring superconducting lines of Y/sub 1/Ba/sub 2/CU/sub 3/O/sub 7-δ/ using films prepared from nitrate and trifluoroacetate solution precursors. A stoichiometric solution of the precursors is sprayed or spun on to the substrate to form a film. The film is patterned by irradiating in selected areas to convert the irradiated layers to an intermediate oxide or fluoride state, the nonirradiated areas being unchanged. The nonirradiated areas are then dissolved away, leaving a pattern of the oxide or fluoride material. This patterned layer is converted to the superconducting 1-2-3 oxide in a subsequent annealing step. Maskless patterning of superconducting films has also been demonstrated by laser-assisted etching of the films in aqueous KOH solution. Although superconductivity is destroyed when the films are placed in solution, it can be restored after a brief anneal in oxygen
Anisotrophic currents and flux jumps in high-Tc superconducting films with self-organized arrays of planar defects

International Nuclear Information System (INIS)

Yurchenko, V.V.; Qviller, A.J.; Mozhaev, P.B.; Mozhaeva, J.E.; Hansen, J.B.; Jacobsen, C.S.; Kotelyanskii, I.M.; Pan, A.V.; Johansen, T.H.

2010-01-01

Regular arrays of planar defects with a period of a few nanometers can be introduced in superconducting YBa 2 Cu 3 O 7-δ (YBCO) thin films by depositing them on vicinal (also called miscut or tilted) substrates. This results in the anisotropy of critical currents flowing in the plane of the film. We present results of real-time magneto-optical imaging (MOI) of magnetic flux distribution and dynamics in a series of YBCO thin films deposited on NdGaO 3 substrates with different miscut angles θ. MOI allows reconstructing the current flow profiles. From the angle formed between domains with different directions of the current flow we determine the anisotropy parameter of the in-plane current, as well as its field and temperature dependences. The artificially introduced defects also have a dramatic effect on the dynamics of the flux propagation: for 10 o o the magnetic flux propagates along the easy channels intermittently, i.e. in a form of flux jumps. This behavior is indicative of thermo-magnetic instability in superconductors, but we argue that this effect can be of a different nature.
Spin dynamics in high-TC superconducting cuprates

International Nuclear Information System (INIS)

Bourges, Ph.

2003-07-01

This work is dedicated to the detailed investigations of the magnetic resonance peak in the superconducting state of cuprates. The existence of such a peak could be the signature of a mechanism linked to magnetism that could explain high critical temperature superconductivity. Inelastic neutron scattering is an adequate tool for the understanding of cuprate properties because it reveals magnetic fluctuations whose behaviour and variety depend strongly on temperature and on the level of doping. The last part of this work is dedicated to the study of spin dynamics in YBa 2 Cu 3 O 6+x system
Epitaxial effects in thin films of high-Tc cuprates with the K2NiF4 structure

Science.gov (United States)

Naito, Michio; Sato, Hisashi; Tsukada, Akio; Yamamoto, Hideki

2018-03-01

La2-xSrxCuO4 (LSCO) and La2-xBaxCuO4 (LBCO) have been recognized as the archetype materials of "hole-doped" high-Tc superconductors. Their crystal structures are relatively simple with a small number of constituent cation elements. In addition, the doping level can be varied by the chemical substitution over a wide range enough to obtain the full spectrum of doping-dependent electronic and magnetic properties. These attractive features have dedicated many researchers to thin-film growth of LSCO and LBCO. The critical temperature (Tc) of LSCO and LBCO is sensitive to strain as manifested by a positive pressure coefficient of Tc in bulk samples. In general, films are strained if they are grown on lattice-mismatched substrates (epitaxial strain). Early attempts (before 1997) at the growth of LSCO and LBCO films resulted in depressed Tc below 30 K as they were grown on a commonly used SrTiO3 substrate (in-plane lattice parameter asub = 3.905 Å): the in-plane lattice parameters of LSCO and LBCO are ≤3.80 Å, and hence tensile epitaxial strain is introduced. The situation was changed by the use of LaSrAlO4 substrates with a slightly shorter in-plane lattice constant (asub = 3.756 Å). On LaSrAlO4 substrates, the Tc reaches 45 K in La1.85Sr0.15CuO4, 47 K in La1.85Ba0.15CuO4, and 56 K in ozone-oxidized La2CuO4+δ films, substantially higher than the Tc's of the bulk compounds. The Tc increase in La1.85Sr0.15CuO4 films on LaSrAlO4 and decrease on SrTiO3 are semi-quantitatively in accord with the phenomenological estimations based on the anisotropic strain coefficients of Tc (dTc/dεi). In this review article, we describe the growth and properties of films of cuprates having the K2NiF4 structure, mainly focusing on the increase/decrease of Tc by epitaxial strain and quasi-stable phase formation by epitaxial stabilization. We further extract the structural and/or physical parameters controlling Tc toward microscopic understanding of the variation of Tc by epitaxial strain.
Superconducting properties of clustered PbBi films

International Nuclear Information System (INIS)

Lobb, C.J.; Tinkham, M.; Klapwijk, T.M.; Smith, A.D.; Harvard Univ., Cambridge, MA

1981-01-01

Superconducting films with high resistance/square have been widely studied as a model of the Kosterlitz-Thouless transition. We show that the behavior of high R clean films near the thickness at which electrical conduction begins is dominated by a few paths across the film and thus should not be interpreted as a Kosterlitz-Thouless transition. Instead, this behavior is consistent with a simple percolation model for the connectivity fluctuations across the film. (orig.)
A high Tc superconducting liquid nitrogen level sensor

International Nuclear Information System (INIS)

Jin, J. X.; Liu, H. K.; Dou, S. X.; Grantham, C.; Beer, J.

1996-01-01

Full text: The dramatic resistance change in the superconducting-normal transition temperature range enables a high T c superconductor to be considered for designing a liquid nitrogen level sensor. A (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10+x Ag clad superconducting wire is selected and tested as a continuous liquid nitrogen level sensor to investigate the possibility for this application. The (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10+x Ag clad superconducting wire has approximately 110 K critical temperature, with more flexible and stable properties compared with bulk shape ceramic high T c superconductors. The voltage drops across the sensor are tested with different immersion lengths in liquid nitrogen. The accuracy of the HTS sensor is analysed with its dR/dT in the superconducting-normal transition range. The voltage signal is sensitive to liquid nitrogen level change, and this signal can be optimized by controlling the transport current. The problems of the Ag clad superconductor are that the Ag sheath thermal conductivity is very high, and the sensor normal resistance is low. These are the main disadvantages for using such a wire as a continuous level sensor. However, a satisfactory accuracy can be achieved by control of the transport current. A different configuration of the wire sensor is also designed to avoid this thermal influence
Analysis of High Tc Superconducting Rectangular Microstrip Patches over Ground Planes with Rectangular Apertures in Substrates Containing Anisotropic Materials

Directory of Open Access Journals (Sweden)

Abderraouf Messai

2013-01-01

Full Text Available A rigorous full-wave analysis of high Tc superconducting rectangular microstrip patch over ground plane with rectangular aperture in the case where the patch is printed on a uniaxially anisotropic substrate material is presented. The dyadic Green’s functions of the considered structure are efficiently determined in the vector Fourier transform domain. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. The accuracy of the analysis is tested by comparing the computed results with measurements and previously published data for several anisotropic substrate materials. Numerical results showing variation of the resonant frequency and the quality factor of the superconducting antenna with regard to operating temperature are given. Finally, the effects of uniaxial anisotropy in the substrate on the resonant frequencies of different TM modes of the superconducting microstrip antenna with rectangular aperture in the ground plane are presented.
Magnetic and Superconducting Materials at High Pressures

Energy Technology Data Exchange (ETDEWEB)

Struzhkin, Viktor V. [Carnegie Inst. of Washington, Washington, DC (United States)

2015-03-24

The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including
Possible universal cause of high-Tc superconductivity in different metals

International Nuclear Information System (INIS)

Amusia, M.Ya.; Shaginyan, V.R.

2002-01-01

Using the theory of the high temperature superconductivity based on the idea of the fermion condensation quantum phase transition (FCQPT) it is shown that neither the d-wave pairing symmetry, nor the pseudogap phenomenon, nor the presence of the Cu-O 2 planes are of decisive importance for the existence of the high-T c superconductivity. The analysis of recent experimental data on this type of superconductivity in different materials is carried out. It is shown that these facts can be understood within the theory of superconductivity based on the FCQPT. The main features of a room-temperature superconductor are discussed [ru
The stability of high-Tc BSCCO/Ag superconducting microcomposites in water, some inorganic solutions and organic solvents

International Nuclear Information System (INIS)

Gao, W.; Chen, J.; Yang, C.O.; McNabb, D.; Sande, J. vander

1992-01-01

Bi(Pb)-Sr-Ca-Cu-O/Ag (BSCCO/Ag) superconducting microcomposites with zero-resistance temperatures from 102 to 108 K and critical current densities of ∝600 A/cm 2 at 77 K were produced by oxidation and annealling of metallic precursor alloys. The stabilities and degradation behavior of BSCCO/Ag specimens in various environments were studied by a combination of mass loss measurement, electrical transport measurement and microstructural observation. The environmental conditions used in the present work were moist air, distilled water, aqueous solutions of NaCl, NaOH and acetic acid, and organic solvents methanol and acetone. Although there is a general tendency toward a decrease in critical current density after a long exposure to most of the testing conditions, the specimens containing a high percent of Ag (≥70 wt.%) showed very little decrease in Tc and J c up to 200 days of exposure in moist air and distilled water, and up to 20 days in NaCl solution, methanol and acetone. It was found that the superconducting ''2223'' phase is stable in water, neutral solutions and the organic solvents, reacts very slowly with basic solutions, and dissolves rapidly in acidic solutions. Some non-superconducting Ca-rich oxides dissolve in water and neutral and basic solutions and therefore damage the connection of the superconducting grains in low-Ag containing specimens. The excellent stability of the BSCCO/Ag superconducting microcomposites containing high Ag provides an important advantage for their potential industrial application. (orig.)

Quasiparticles in the superconducting state of high-Tc metals

International Nuclear Information System (INIS)

Amusia, M.Ya.; Shaginyan, V.R.

2003-01-01

The behavior of quasiparticles in the superconducting state of high-T c metals within the framework of the theory of superconducting state based on the fermion condensation quantum phase transition is considered. It is shown that the behavior coincides with the behavior of Bogoliubov quasiparticles, whereas the maximum value of the superconducting gap and other exotic properties are determined by the presence of the fermion condensate. If at low temperatures the normal state is recovered by the application of a magnetic field suppressing the superconductivity, the induced state can be viewed as Landau-Fermi liquid. These observations are in good agreement with recent experimental facts [ru
Magnetization Controlled Superconductivity in a Film with Magnetic Dots

International Nuclear Information System (INIS)

Lyuksyutov, I.F.; Pokrovsky, V.; Pokrovsky, V.

1998-01-01

We consider a superconducting film with a magnetic dots array (MDA) placed upon it. Magnetic moments of the dots are normal to the film and strong enough to create vortices in the superconducting film. Magnetic interaction between dots is negligible. Zero-field cooling leads to random magnetization of the MDA well above the superconducting temperature. With this cooling, the film is in a resistive state below the (expected) superconducting transition. Paradoxically, when field cooled, the film with MDA can be superconducting. copyright 1998 The American Physical Society
Relations between structural and superconducting properties of bulk and thin film high-Tc materials

International Nuclear Information System (INIS)

Hessel Andersen, N.

1994-06-01

The structural ordering of oxygen deficient and Co-doped YBCO (YBa 2 Cu 3-y Co y O 6+x ) have been studied experimentally, and by computer simulations of the oxygen ordering in the basal plane of the structure. The calculations are based on the two-dimensional ASYNNNI model and its modifications. Good agreement is established between the ASYNNNI calculations and the experimentally observed structural properties of the double cell ortho-II structure and the oxygen disordering process from Co-doping into the basal plane. A model that relates the superconducting transition temperature T c (x) of undoped YBCO and T c (y) of Co-doped YBCO to the formation of specific domains of the two orthorhombic ordered oxygen phases, ortho-I and ortho-II, shows a close agreement with experimental T c (x) and T c (y) data of samples prepared under equilibrium conditions. The structural changes as a result of metal ion substitutions and oxidation/reduction processes have been studied by neutron powder diffraction in Pb 2 Sr 2 Ln 1-x Ca x Cu 3 O 8+y (Ln = Y and Ho), Nd 1.85 Ce 0.15 CuO 4+y , and chemically oxidized La 2-x Sr x CuO 4+y 2 Cu 3-y Al y O 6+x (y 2 Cu 3 O 6+x and Bi 2 Sr 2 CaCu 2 O 8+x thin films deposited on SrTiO 3 (001), MgO (001), LaAlO 3 (001), and NdGaO 3 (001) substrates has been studied by x-ray diffraction, TEM and RBS, and the structural ordering has been analysed in relation to their superconducting properties. (au) (30 ills., 29 refs.)
Investigation of thin films, heterostructures and devices of ceramic superconductors by means of high-resolution electron microscopy

International Nuclear Information System (INIS)

Jia Chunlin.

1993-08-01

In this thesis a systematic study of the microstructure of YBa 2 Cu 3 O 7 thin films is presented by means of high-resolution electron microscopy (HREM). Most of the efforts are focused on the characterization of heterostructures of superconducting YBa 2 Cu 3 O 7 and non-superconducting PrBa 2 Cu 3 O 7 and on YBa 2 Cu 3 O 7 films deposited on step-edge substrates. These specially designed structures exhibit a great potential for the electronic application of high-Tc superconductors and for the investigation of the basic electric properties of the YBa 2 Cu 3 O 7 superconductor. (orig.) [de
Preparation of textured high Tc superconducting films by CVD using halides on technical substrates with appropriate buffer layers. Final report

International Nuclear Information System (INIS)

Selbmann, D.; Balarin, M.; Klosowski, J.

1993-01-01

On the basis of a thermodynamical calculation of the system Y-Ba-Cu-O-Hal-C-H, Hal = I, Br, Cl the deposition conditions of the 123-phase and the other phases in this system was investigated. For the practical applications a reaction temperature higher 850 C and an oxidizer excesse higher 5 . 10 3 is necessary in order to deposit halid- and carbon free layers. A new Aerosol-CVD-process has been developed, which allows the reproducible preparation of superconducting YBa 2 Cu 3 O 7 thin films. The process uses a solution source of Y-, Ba-, Cu-bromide dissolved in suitable organic solvents. With the process the films consisting of the 123-phase, however the content of other phases is too high. With this composition it is not possible to deposit textured layers. This behaviour is due to flow technical problems. In order to avoid the formation of oxides in the evaporator it is necessary to mix the oxidizer directly near the substrate. Therefore the development of a new reactor and a process optimization is necessary. (orig.) [de
Electrochemical investigations of high-Tc superconductors - low-temperature electrochemistry

International Nuclear Information System (INIS)

Lorenz, W.J.

1992-01-01

This research report presents a summary of results obtained by electrochemical investigations of high-Tc superconductors at room temperature and below the critical temperature (Tc). The studies were to reveal the behaviour of the ceramic superconducting materials at the interface between superconductor and ionic conductor. (MM) With 4 tabs., 8 figs [de
Possibility of high temperature superconducting phases in PdH

Science.gov (United States)

Tripodi, Paolo; Di Gioacchino, Daniele; Borelli, Rodolfo; Vinko, Jenny Darja

2003-05-01

Possible new superconducting phases with a high critical transition temperature (Tc) have been found in stable palladium-hydrogen (PdHx) samples for stoichiometric ratio x=H/Pd⩾1, in addition to the well-known low critical transition temperature (0⩽Tc⩽9) when x is in the range (0.75⩽x⩽1.00). Possible new measured superconducting phases with critical temperature in the range 51⩽Tc⩽295 K occur. This Tc varies considerably with every milli part of x when x exceeds unit. A superconducting critical current density Jc⩾6.1×104 A cm-2 has been measured at 77 K with HDC=0 T.
Microscopic Superconductivity and Room Temperature Electronics of High-Tc Cuprates

International Nuclear Information System (INIS)

Liu Fusui; Chen Wanfang

2008-01-01

This paper points out that the Landau criterion for macroscopic superfluidity of He II is only a criterion for microscopic superfluidity of 4 He, extends the Landau criterion to microscopic superconductivity in fermions (electron and hole) system and system with Cooper pairs without long-range phase coherence. This paper gives another three non-superconductive systems that are of microscopic superconductivity. This paper demonstrates that one application of microscopic superconductivity is to establish room temperature electronics of the high-T c cuprates
High Tc Superconducting Magnet Excited by a Semiconductor Thermoelectric Element

Science.gov (United States)

Kuriyama, T.; Ono, M.; Tabe, S.; Oguchi, A.; Okamura, T.

2006-04-01

A high Tc superconducting (HTS) magnet excited by a thermal electromotive force of a thermoelectric element is studied. This HTS magnet has the advantages of compactness, lightweight and continuous excitation in comparison with conventional HTS magnets, because this HTS magnet does not need a large external power source. In this system, a heat input into the cryogenic environment is necessary to excite the thermoelectric element for constant operation. This heat generation, however, causes a rise in temperature of an HTS coil and reduces the system performance. In this paper, a newly designed magnet system which adopted a two-stage GM cryocooler was investigated. It enabled us to control the temperature of a thermoelectric element and that of an HTS coil independently. The temperature of the HTS coil could be kept at 10-20 K at the second stage of the GM cryocooler, while the thermoelectric element could be excited at higher temperature in the range of 50-70 K at the first stage, where the performance of the thermoelectric element was higher. The experimental results on this HTS magnet are shown and the possibility of the thermoelectric element as a main power source of the HTS magnets is discussed.
Flux Flow, Pinning, and Resistive Behavior in Superconducting Networks

International Nuclear Information System (INIS)

Stephen Teitel

2005-01-01

Numerical simulators are used to study the behavior of interacting quantized vortices and vortex lines in superconducting networks, films, and three dimensional bulk samples. An emphasis is on the explanation of the phenomenological behavior of the ''high-Tc'' copper-oxide superconductors and related model systems
Characterization of the microwave properties of superconducting films with high transition temperature

International Nuclear Information System (INIS)

Richter, W.; Klinger, M.; Daginnus, M.

1989-01-01

In the meantime high quality Y-Ba-Cu-O thin films were produced. The latest results show, that its surface resistances are clearly lower than the values of copper, measured at a temperature of 77 K and up to frequencies of 86 GHz. This examination had the aim to produce high-T c films with a simple and low cost method, to use them as transmission lines at frequencies up to 30 GHz and above. A screen printing process was investigated, and high-T c thick films were fabricated on several substrates. Superconducting transition temperatures up to 80 K (dc zero resistance) were obtained. The films showed no complete magnetic shielding, and its microwave surface resistances were clearly higher than that ones for copper. The a. c. Josephson effect was proved with granular structures of bulk Y-Ba-Cu-O material and with screen printed thick films. Because of its high surface resistances, these thick films are unsuitable for the use as transmission lines at high frequencies. However, the a.c. Josephson effect can be used to manufacture microwave sensors in bulk Y-Ba-Cu-O and screen printed films of Y-Ba-Cu-O, which have a favourable geometric structure. (orig.) With 16 refs., 2 tabs., 24 figs [de
Epitaxial YBa2Cu3O7 films on rolled-textured metals for high temperature superconducting applications

International Nuclear Information System (INIS)

Norton, D.P.; Park, C.; Prouteau, C.

1998-04-01

The epitaxial growth of high temperature superconducting (HTS) films on rolled-textured metal represents a viable approach for long-length superconducting tapes. Epitaxial, 0.5 microm thick YBa 2 Cu 3 O 7 (YBCO) films with critical current densities, J c , greater than 1 MA/cm 2 have been realized on rolled-textured (001) Ni tapes with yttria-stabilized zirconia (YSZ)/CeO 2 oxide buffer layers. This paper describes the synthesis using pulsed-laser deposition (PLD) of epitaxial oxide buffer layers on biaxially-textured metal that comprise the so-called rolling-assisted biaxially-textured substrates (RABiTs trademark). The properties of the buffer and YBa 2 Cu 3 O 7 films on rolled-textured Ni are discussed, with emphasis given to the crystallographic and microstructural properties that determine the superconducting properties of these multilayer structures
High {Tc} superconductivity: Symmetries and reflections

International Nuclear Information System (INIS)

Zhang, S.C.

1999-01-01

This is a talk given at the Symposium Symmetries and Reflections, dedicated to Prof. C.N. Yang's retirement. In this talk, the author reflects on his personal interaction with Prof. Yang since his graduate career at SUNY Stony Brook, and his profound impact on his understanding of theoretical physics. He also reviews the SO(5) theory of high T c superconductivity and shows how his collaboration with Prof. Yang in 1990 lead to the foundation of this idea
Phases and structural characteristics of high Tc superconducting oxide in (Bi, Pb)-Sr-Ca-Cu-O system

International Nuclear Information System (INIS)

Chen, Zuyano; Li, Zhengrong; Qian, Yitai; Zhou, Quien; Cheng, Tingzhu

1989-01-01

The various phases, which are responsible for variant maximum d-value including 18.5 angstrom, 15.4 angstrom, 12.2 angstrom, 6.2 angstrom, 3.2 angstrom and possible 9.1 angstrom respectively, observed in high Tc superconducting complex oxide of (Bi,Pb)-Sr-Ca-Cu-O system are reported in this paper according to the result of X-ray diffraction on platelike crystals or crystallites synthesized under different preparation conditions. The phase of tetragonal system with c=3.21 angstrom, a=3.86 angstrom is possible parent structural unit and it is of great significance to the structure constitution of various phases with large lattice parameter c and structural characteristics of superconducting oxide. In view of the above a model of two-dimension stack-up which causes a stack in variant styles along c-axis and constitute various phases with different lattice parameter c is proposed and discussed
Superstrate loading effects on the resonant characteristics of high Tc superconducting circular patch printed on anisotropic materials

Science.gov (United States)

Bedra, Sami; Bedra, Randa; Benkouda, Siham; Fortaki, Tarek

2017-12-01

In this paper, the effects of both anisotropies in the substrate and superstrate loading on the resonant frequency and bandwidth of high-Tc superconducting circular microstrip patch in a substrate-superstrate configuration are investigated. A rigorous analysis is performed using a dyadic Galerkin's method in the vector Hankel transform domain. Galerkin's procedure is employed in the spectral domain where the TM and TE modes of the cylindrical cavity with magnetic side walls are used in the expansion of the disk current. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. London's equations and the two-fluid model of Gorter and Casimir are used in the calculation of the complex surface impedance of the superconducting circular disc. The accuracy of the analysis is tested by comparing the computed results with previously published data for several anisotropic substrate-superstrate materials. Good agreement is found among all sets of results. The numerical results obtained show that important errors can be made in the computation of the resonant frequencies and bandwidths of the superconducting resonators when substrate dielectric anisotropy, and/or superstrate anisotropy are ignored. Other theoretical results obtained show that the superconducting circular microstrip patch on anisotropic substrate-superstrate with properly selected permittivity values along the optical and the non-optical axes combined with optimally chosen structural parameters is more advantageous than the one on isotropic substrate-superstrate by exhibiting wider bandwidth characteristic.
Raman scattering diagnostics of YBa2Cu3Ox high temperature superconducting films

International Nuclear Information System (INIS)

Bagratashvili, V.N.; Burimov, V.N.; Denisov, V.N.

1988-01-01

Superconducting YBa 2 Cu 3 O x films produced by laser spraying of ceramic material are investigated by light Raman scattering (LCS). It is shown that using LCS it is possible to obtain data on phase composition and prevailing film orientation and to find optical conditions for their synthesis. The LCS method feature consists in a possibility of non-destructive remote control and high space resolution (several microns). Experimental results have shown that the best parameters (the highest T c and the narrowest Δ T c interval) are typical of films with prevailing orientation of 0 xy crystallite plane parallel to the surface
Amorphous-like interfacial layer between a high-Tc superconducting Tl-1223 film and a Ag substrate examined by high-voltage high-resolution transmission electron microscopy

International Nuclear Information System (INIS)

Kim, Bongjun; Kim, Hyuntak; Nagai, Takuro; Matsui, Yoshio; Horiuchi, Shigeo; Jeong, Daeyeong; Deinhofer, Christian; Gritzner, Gerhard; Kim, Youngmin; Kim, Younjoong

2006-01-01

The thin amorphous-like layer, formed at the interface between a high-T c superconducting (Tl 0.5 , Pb 0.5 )(Sr 0.8 , Ba 0.2 )Ca 2 Cu 3 O y (Tl-1223) film and a Ag substrate during heating at 910 .deg. C, has been examined by using high-voltage high-resolution transmission electron microscopy. The interfacial layer is less than 10 nm in thickness. It contacts the (001) plane of Tl-1223 and the (113) or (133) planes of Ag in most cases. Its composition is similar to that of Tl-1223, except for the inclusion of a substantial amount of Ag. Its formation proceeds by diffusion of Ag into Tl-1223, during which a structure change first occurs at the layer of CuO 2 + Ca planes. The Tl(Pb)O + the Sr(Ba)O layers are then destroyed to cause the total structure to become amorphous-like. Furthermore, we have found that it is formed under an irradiation of highly energetic electrons.
On the application of High-Tc superconductors in power coils and transformers

NARCIS (Netherlands)

Chevtchenko, O.A.

2002-01-01

In this study, the electro-magnetic properties of high-Tc tapes and coils are investigated. The focus is on Bi-2223/Ag tapes with non-twisted superconducting filaments as these are the only high-Tc superconductors at present available in sufficient length for practical applications. The study is
Spin-polarons and high-Tc superconductivity

International Nuclear Information System (INIS)

Wood, R.F.

1994-03-01

The spin-polaron concept is introduced in analogy to ionic and electronic polarons and the assumptions underlying the author's approach to spin-polaron mediated high-T c superconductivity are discussed. Elementary considerations about the spin-polaron formation energy are reviewed and the possible origin of the pairing mechanism illustrated schematically. The electronic structure of the CuO 2 planes is treated from the standpoint of antiferromagnetic band calculations that lead directly to the picture of holes predominantly on the oxygen sublattice in a Mott-Hubbard/charge transfer insulator. Assuming the holes to be described in a Bloch representation but with the effective mass renormalized by spin-polaron formation, equations for the superconducting gap, Δ, and transition temperature, T c , are developed and the symmetry of Δ discussed. After further simplifications, T c is calculated as a function of the carrier concentration, x. It is shown that the calculated behavior of T c (x) follows the experimental results closely and leads to a natural explanation of the effects of under- and over-doping. The paper concludes with a few remarks about the evidence for the carriers being fermions (polarons) or bosons (bipolarons)
Raman scattering and luminescence of high-Tc superconducting oxides

International Nuclear Information System (INIS)

Eremenko, V.V.; Gnezdilov, V.P.; Fomin, V.I.; Fugol', I.Ya.; Samovarov, V.N.

1989-01-01

Raman and luminescence spectra of high-T c superconducting oxides are summarized, mainly YBa 2 Cu 3 O 7-σ and partly La 2-x Ba x CuO 4-σ . In raman spectra we succeeded to distinguish electron scattering to define the energy gap Δ in the superconducting state. The luminescence spectra are due to the emission of oxygen and interaction with conduction electrons. 70 refs.; 13 figs

MgB2 ultrathin films fabricated by hybrid physical chemical vapor deposition and ion milling

Directory of Open Access Journals (Sweden)

Narendra Acharya

2016-08-01

Full Text Available In this letter, we report on the structural and transport measurements of ultrathin MgB2 films grown by hybrid physical-chemical vapor deposition followed by low incident angle Ar ion milling. The ultrathin films as thin as 1.8 nm, or 6 unit cells, exhibit excellent superconducting properties such as high critical temperature (Tc and high critical current density (Jc. The results show the great potential of these ultrathin films for superconducting devices and present a possibility to explore superconductivity in MgB2 at the 2D limit.
New Fast Response Thin Film-Based Superconducting Quench Detectors

CERN Document Server

Dudarev, A; van de Camp, W; Ravaioli, E; Teixeira, A; ten Kate, H H J

2014-01-01

Quench detection on superconducting bus bars and other devices with a low normal zone propagation velocity and low voltage build-up is quite difficult with conventional quench detection techniques. Currently, on ATLAS superconducting bus bar sections, superconducting quench detectors (SQD) are mounted to detect quench events. A first version of the SQD essentially consists of an insulated superconducting wire glued to a superconducting bus line or windings, which in the case of a quench rapidly builds up a relatively high resistance that can be easily and quietly detected. We now introduce a new generation of drastically improved SQDs. The new version makes the detection of quenches simpler, more reliable, and much faster. Instead of a superconducting wire, now a superconducting thin film is used. The layout of the sensor shows a meander like pattern that is etched out of a copper coated 25 mu m thick film of Nb-Ti glued in between layers of Kapton. Since the sensor is now much smaller and thinner, it is easi...
Superconducting thin films

International Nuclear Information System (INIS)

Hebard, A.F.; Vandenberg, J.M.

1982-01-01

This invention relates to granular metal and metal oxide superconducting films formed by ion beam sputter deposition. Illustratively, the films comprise irregularly shaped, randomly oriented, small lead grains interspersed in an insulating lead oxide matrix. The films are hillock-resistant when subjected to thermal cycling and exhibit unusual josephson-type switching characteristics. Depending on the oxygen content, a film may behave in a manner similar to that of a plurality of series connected josephson junctions, or the film may have a voltage difference in a direction parallel to a major surface of the film that is capable of being switched from zero voltage difference to a finite voltage difference in response to a current larger than the critical current
Size and dimensionality effects in superconducting Mo thin films

International Nuclear Information System (INIS)

Fabrega, L; Gil, O; Camon, A; Parra-BorderIas, M; Fernandez-MartInez, I; Costa-Kraemer, J L; Briones, F; Sese, J; Gonzalez-Arrabal, R

2011-01-01

Molybdenum is a low T c , type I superconductor whose fundamental properties are poorly known. Its importance as an essential constituent of new high performance radiation detectors, the so-called transition edge sensors (TESs) calls for better characterization of this superconductor, especially in thin film form. Here we report on a study of the basic superconducting features of Mo thin films as a function of their thickness. The resistivity is found to rise and the critical temperature decreases on decreasing film thickness, as expected. More relevant, the critical fields along and perpendicular to the film plane are markedly different, thickness dependent and much larger than the thermodynamic critical field of Mo bulk. These results are consistent with a picture of type II 2D superconducting films, and allow estimates of the fundamental superconducting lengths of Mo. The role of morphology in determining the 2D and type II character of the otherwise type I molybdenum is discussed. The possible consequences of this behaviour on the performance of radiation detectors are also addressed.
Conductive polymer/high-TC superconductor sandwich structures: An example of a molecular switch for controlling superconductivity

International Nuclear Information System (INIS)

McDevitt, J.T.; Haupt, S.G.; Lo, R.K.

1994-01-01

The preparation of a hybrid conducting polymer/high-temperature superconductor device consisting of a polypyrrole coated YBa 2 Cu 3 O 7-x microbridge is reported. Electrochemical techniques are exploited to alter the oxidation state of the polymer and, in doing so, it is found for the first time that superconductivity can be modulated in a controllable and reproducible fashion by a polymer layer. Whereas the neutral (insulating) polypyrrole only slightly influences the electrical properties of the underlying YBa 2 Cu 3 O 7- film, the oxidized (conductive) polymer depresses T c by up to 50K. In a similar fashion, the oxidation state of the polymer is found to modulate reversibly the magnitude of J c , the superconducting critical current. Thus, a new type of molecular switch for controlling superconductivity is demonstrated. Electrochemical, resistance vs. temperature, atomic force microscopy and scanning electron microscopy measurements are utilized to explore the polymer/superconductor interactions
Feshbach shape resonance for high Tc pairing in superlattices of quantum stripes and quantum wells

Directory of Open Access Journals (Sweden)

A Bianconi

2006-09-01

Full Text Available The Feshbach shape resonances in the interband pairing in superconducting superlattices of quantum wells or quantum stripes is shown to provide the mechanism for high Tc superconductivity. This mechanism provides the Tc amplification driven by the architecture of material: superlattices of quantum wells (intercalated graphite or diborides and superlattices of quantum stripes (doped high Tc cuprate perovskites where the chemical potential is tuned to a Van Hove-Lifshitz singularity (vHs in the electronic energy spectrum of the superlattice associated with the change of the Fermi surface dimensionality in one of the subbands.
Characterization of the superconducting state in hafnium hydride under high pressure

Science.gov (United States)

Duda, A. M.; Szewczyk, K. A.; Jarosik, M. W.; Szcześniak, K. M.; Sowińska, M. A.; Szcześniak, D.

2018-05-01

The hydrogen-rich compounds at high pressure may exhibit notably high superconducting transition temperatures. In the paper, we have calculated the basic thermodynamic parameters of the superconducting state in two selected phases of HfH2 hydride under high-pressure respectively at 180 GPa for Cmma and 260 GPa for P21 / m . Calculations has been conducted in the framework of the Eliashberg formalism. In particular, we have determined the values of the critical temperature (TC) to be equal to 8 K and 13 K for the Cmma and P21 / m phases, respectively. Moreover, we have estimated other thermodynamic properties such as the order parameter (Δ (T)) , the thermodynamic critical field (HC (T)) , and the specific heat for the normal (CN) and superconducting (CS) state. Finally, we have shown that the characteristic ratios: RΔ = 2 Δ (0) /kBTC and RC = ΔC (TC) /CN (TC) , which are related to the above thermodynamic functions, slightly differ from the predictions of the Bardeen-Cooper-Schrieffer theory due to the strong-coupling and retardation effects.
Magnetic shield effect simulation of superconducting film shield covering directly coupled HTS dc-SQUID magnetometer

International Nuclear Information System (INIS)

Terauchi, N.; Noguchi, S.; Igarashi, H.

2011-01-01

A superconducting film shield over a SQUID ring improves the robustness of the SQUID with respect to magnetic noise. Supercurrent in the SQUID magnetometer and the superconducting film shield were simulated. The superconducting film shield reduces the influence of the external magnetic field on the SQUID ring. An HTS SQUID is a high sensitive magnetic sensor. In recent years, the HTS SQUID is widely used in various applications. In some applications, high robustness with respect to magnetic noise is required to realize stable operation at outside of a magnetic shielding room. The target of this paper is a directly coupled HTS dc-SQUID magnetometer. To enhance the robustness of the SQUID magnetometer, use of a superconducting thin film shield has been proposed. The magnetic field directly penetrating the SQUID ring causes the change of the critical current of Josephson junction, and then the SQUID magnetometer transitions into inoperative state. In order to confirm the magnetic shield effect of the superconducting film shield, electromagnetic field simulation with 3D edge finite element method was performed. To simulate the high temperature superconductor, E-J characteristics and c-axis anisotropy are considered. To evaluate the effect of the superconducting film shield, an external magnetic field which is supposed to be a magnetic noise is applied. From the simulation results, the time transition of the magnetic flux penetrating the SQUID ring is investigated and the effect of the superconducting film shield is confirmed. The amplitude of the magnetic flux penetrating the SQUID ring can be reduced to about one-sixth since the superconducting film shield prevents the magnetic noise from directly penetrating the SQUID ring.
Five-fold way to new high Tc superconductors

Indian Academy of Sciences (India)

shook the foundation of phonon-mediated pairing mechanism. In fact, certain in- ...... of superconducting Tc in doped cuprates below optimal doping. ...... ductor transition, the following are the minimal requirements for superconductivity:.
Excessive current in wide superconducting films

International Nuclear Information System (INIS)

Volotskaya, V.G.; Sivakov, A.G.; Turutanov, O.G.

1986-01-01

The resistive state of a wide long film due to superconductivity destruction by current is studied. The voltage-independent excess current I 0 is observed on I-V curves at high transport currents. The two-dimensional image of the current-carrying sample obtained by laser scanning technique in this current range indicates that the whole film is in the resistive state. The current I 0 is measured as a function of magnetic field and SHF power
Tc enhancement and superconducting properties of a YBa[sub 2]Cu[sub 3]O[proportional to]6. 5 thin film after fluorine insertion

Energy Technology Data Exchange (ETDEWEB)

Pena, O.; Mokhtari, M.; Perrin, C.; Thivet, C.; Guilloux-Viry, M.; Perrin, A.; Sergent, M. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France))

1993-02-10

An oxygen-deficient YBa[sub 2]Cu[sub 3]O[sub x] thin film (Tc=54 K, [Delta]Tc>8K) was treated under a diluted (3% in N[sub 2]) NF[sub 3] gas flow at temperatures not exceeding 280degC. AC induction measurements show a substantial increase of Tc up to about 86 K and a clear improvement of the [chi]''[sub AC] dissipation component (FWHM=1.2 K), as a function of the reaction time. The film was further studied at the end of the reaction by the AC-field dependence and by DC magnetization measurements, including ZFC/FC and magnetization cycles. It was found that granular effects are not important, meaning that the crystalline properties of the film are not degraded by the fluorination process, in good agreement with the X-ray diffraction data. The sharpness of the [chi]''[sub AC] peak, the low M[sub FC]/M[sub ZFC] ratio and the large hysteresis of the magnetization cycle indicate that the critical current densities are high (of the order of 10[sup 6] A/cm[sup 2] at 5 K) and comparable to reasonably good YBa[sub 2]Cu[sub 3]O[sub 7] thin films. The usefulness of the fluorination method and a comparison with halogenated YBa[sub 2]Cu[sub 3]O[sub x] ceramics are also presented. (orig.).
High-Tc superconductivity near the anion height instability in Fe-based superconductors: analysis of LaFeAsO(1-x)H(x).

Science.gov (United States)

Onari, Seiichiro; Yamakawa, Youichi; Kontani, Hiroshi

2014-05-09

The isostructural transition in the tetragonal phase with a sizable change in the anion height, is realized in heavily H-doped LaFeAsO and (La,P) codoped CaFe2As2. In these compounds, the superconductivity with higher Tc (40-50 K) is realized near the isostructural transition. To find the origin of the anion-height instability and the role in realizing the higher-Tc state, we develop the orbital-spin fluctuation theory by including the vertex correction. We analyze LaFeAsO(1-x)H(x) and find that the non-nematic orbital fluctuations, which induce the anion-height instability, are automatically obtained at x∼0.5, in addition to the conventional nematic orbital fluctuations at x∼0. The non-nematic orbital order triggers the isostructural transition, and its fluctuation would be a key ingredient to realize higher-Tc superconductivity of order 50 K.
A novel propulsion method for high-Tc superconducting maglev vehicle

International Nuclear Information System (INIS)

Ma Guangtong; Wang Jiasu; Wang Suyu; Liu Minxian; Jing Hua; Lu Yiyun; Lin Qunxu

2008-01-01

High-Tc superconducting (HTS) maglev is considered as a perfect transportation type because of its unique inherent stability. A direct current (DC) linear motor using the permanent magnet guideway (PMG) as the stator and the on-board coil as the rotor instead of the present inductive or synchronous alternate current (AC) linear motor which has an economic disadvantage due to the necessity to lay primary coil along the guideway is proposed in this paper. In order to modulate the magnetic field under the PMG, an inverse E shape ferromagnetic device (IESFD) core is designed. The possible winding method for the on-board coil is listed, and the analytical result shows that a considerable net ampere force and thus the propulsion force can be generated by this special structure. The influence of the concentrated effect of the IESFD on the maglev performance of HTS bulk is studied by a numerical program, and the results show that the levitation force with the IESFD is 90% of that without. It is also indicated that the load capability and lateral performance of the maglev vehicle combined this propulsion method can be improved thanks to the attractive effect between the IESFD and PMG. The cost of the HTS maglev vehicle will be remarkably reduced and then shorten the distance to practical application with this propulsion method
A novel propulsion method for high- Tc superconducting maglev vehicle

Science.gov (United States)

Ma, Guangtong; Wang, Jiasu; Wang, Suyu; Liu, Minxian; Jing, Hua; Lu, Yiyun; Lin, Qunxu

2008-01-01

High-Tc superconducting (HTS) maglev is considered as a perfect transportation type because of its unique inherent stability. A direct current (DC) linear motor using the permanent magnet guideway (PMG) as the stator and the on-board coil as the rotor instead of the present inductive or synchronous alternate current (AC) linear motor which has an economic disadvantage due to the necessity to lay primary coil along the guideway is proposed in this paper. In order to modulate the magnetic field under the PMG, an inverse E shape ferromagnetic device (IESFD) core is designed. The possible winding method for the on-board coil is listed, and the analytical result shows that a considerable net ampere force and thus the propulsion force can be generated by this special structure. The influence of the concentrated effect of the IESFD on the maglev performance of HTS bulk is studied by a numerical program, and the results show that the levitation force with the IESFD is 90% of that without. It is also indicated that the load capability and lateral performance of the maglev vehicle combined this propulsion method can be improved thanks to the attractive effect between the IESFD and PMG. The cost of the HTS maglev vehicle will be remarkably reduced and then shorten the distance to practical application with this propulsion method.
High field properties of superconducting BaFe{sub 2-x}Ni{sub x}As{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Richter, Stefan [Institute for Metallic Materials, IFW Dresden (Germany); Technical University Dresden (Germany); Kurth, Fritz; Grinenko, Vadim; Nielsch, Kornelius; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Iida, Kazumasa [Nagoya University (Japan); Pervakov, Kirill [Russian Academy of Sciences (Russian Federation); Tarantini, Chiara; Jaroszynski, Jan [National High Magnetic Field Laboratory (United States); Pukenas, Aurimas; Skrotzki, Werner [Technical University Dresden (Germany)

2016-07-01

Fe based superconductors combine the advantages of cuprates (high upper critical field) with the small Hc{sub 2} anisotropy of classic low temperature superconductors, which makes them suitable candidates for high field applications. The study of Fe-based superconducting thin films is one crucial step to explore this potential in more detail. We present results for epitaxial BaFe{sub 2-x}Ni{sub x}As{sub 2} thin films, which have been successfully grown for the first time using pulsed laser deposition. Superconducting transition temperatures of up to 19 K have been realized in slightly overdoped films, which is in good agreement with results obtained for single crystals. The behavior of the upper critical field and critical current density has been measured in high magnetic fields up to 35 T. The results will be correlated to the observed microstructure and compared to high field data for single crystals with similar composition.
Construction of sputtering system and preparation of high temperature superconducting thin films

International Nuclear Information System (INIS)

Kaynak, E.

2000-01-01

The preparation of high T c superconducting thin film is important both for the understanding of fundamental behaviours of these materials and for the investigations on the usefulness of technological applications. High quality thin films can be prepared by various kinds of techniques being used today. Among these, sputtering is the most preferred one. The primary aim of this work is the construction of a r. f. and c. magnetron sputtering system. For this goal, a magnetron sputtering system was designed and constructed having powers up to 500W (r.f.) and 1KW (d.c.) that enables to deposit thin films of various kinds of materials: metals, ceramics and magnetic materials. The temperature dependence of the electrical resistance of the films was investigated by using four-point probe method. The zero resistance and the transition with of the films were measured as 80-85 K, and 2-9 K, respectively. The A.C. susceptibility experiments were done by utilising the system that was designed and constructed. The applied field dependence of the real and imaginary components of the susceptibility that were measured between the 77-120 K temperature interval and at a fixed frequency was investigated
Bi-based superconducting fibers with high critical parameters

International Nuclear Information System (INIS)

Huo Yujing; He Yusheng; Liu Menglin; Mao Sining; Cai Liying; Wang Ying; Zhang Jincang; He Aisheng; Wang Jinsong

1991-01-01

Superconducting fibers of Bi(Pb)-Sr-Ca-Cu-O high Tc superconducting materials have been prepared by means of the laser-heated pedestal growth (LHPG) method. The highest zero resistance temperature T c0 reaches is 114K, and the highest critical current density J c (77K, O T) is greater than 5000 A/cm 2 . As-grown superconducting fibers were successfully fabricated without post growth heat treatment. Amorphous materials were used for the first time to make high quality fibers. The influence of growth conditions, thermal treatment and the composition of the fibers were discussed. (author). 5 refs., 7 figs., 3 tabs
Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.

Science.gov (United States)

Asaba, Tomoya; Wang, Yongjie; Li, Gang; Xiang, Ziji; Tinsman, Colin; Chen, Lu; Zhou, Shangnan; Zhao, Songrui; Laleyan, David; Li, Yi; Mi, Zetian; Li, Lu

2018-04-25

In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe 2 ). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe 2 thin films with a high precision rotation stage, we map the upper critical field H c2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field H c2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of H c2 in Ising superconductors.
Superconducting fluctuations and pseudogap in high-Tc cuprates

Directory of Open Access Journals (Sweden)

Alloul H.

2012-03-01

Full Text Available Large pulsed magnetic fields up to 60 Tesla are used to suppress the contribution of superconducting fluctuations (SCF to the ab-plane conductivity above Tc in a series of YBa2Cu3O6+x. These experiments allow us to determine the field Hc’(T and the temperature Tc’ above which the SCFs are fully suppressed. A careful investigation near optimal doping shows that Tc’ is higher than the pseudogap temperature T*, which is an unambiguous evidence that the pseudogap cannot be assigned to preformed pairs. Accurate determinations of the SCF contribution to the conductivity versus temperature and magnetic field have been achieved. They can be accounted for by thermal fluctuations following the Ginzburg-Landau scheme for nearly optimally doped samples. A phase fluctuation contribution might be invoked for the most underdoped samples in a T range which increases when controlled disorder is introduced by electron irradiation. Quantitative analysis of the fluctuating magnetoconductance allows us to determine the critical field Hc2(0 which is found to be be quite similar to Hc’ (0 and to increase with hole doping. Studies of the incidence of disorder on both Tc’ and T* allow us to to propose a three dimensional phase diagram including a disorder axis, which allows to explain most observations done in other cuprate families.
Thin films for emerging applications v.16

CERN Document Server

Francombe, Maurice H

1992-01-01

Following in the long-standing tradition of excellence established by this serial, this volume provides a focused look at contemporary applications. High Tc superconducting thin films are discussed in terms of ion beam and sputtering deposition, vacuum evaporation, laser ablation, MOCVD, and other deposition processes in addition to their ultimate applications. Detailed treatment is also given to permanent magnet thin films, lateral diffusion and electromigration in metallic thin films, and fracture and cracking phenomena in thin films adhering to high-elongation substrates.

Structural, electronic, superconducting and mechanical properties of ReC and TcC

Energy Technology Data Exchange (ETDEWEB)

Kavitha, M.; Priyanga, G. Sudha; Rajeswarapalanichamy, R., E-mail: rajeswarapalanichamy@gmail.com; Santhosh, M. [Department of Physics, N.M.S.S.V.N College, Madurai, Tamilnadu-625019 (India)

2015-06-24

The structural, electronic, superconducting and mechanical properties of ReC and TcC are investigated using density functional theory calculations. The lattice constants, bulk modulus, and the density of states are obtained. The calculated lattice parameters are in good agreement with the available results. The density of states reveals that ReC and TcC exhibit metallic behavior at ambient condition. A pressure-induced structural phase transition is observed in both materials.
Preparation of Bi-Pb-Sr-Ca-Cu-O high Tc thick films on Ag or MgO substrate with superconductor paste; Bi kei ko Tc chodendo paste ni yoru Ag, MgO kibanjo eno atsumaku sakusei

Energy Technology Data Exchange (ETDEWEB)

Takabatake, N. [Ishikawa Technical High School, Ishikawa (Japan); Tsubota, T.; Ishikawa, T.; Ohashi, K. [Kanazawa Institute of Technology, Ishikawa (Japan)

1995-07-15

The following were reported on making Bi series superconducting thick films by a wet method. A paste was made by adding PSO (or ethanol solution of ethylenegrycol) of Yushiro Chemical Industry Co., Ltd. as a binder to a Bi series 2223 single-phase powder sample (blending composition Bi:Pb:Sr:Ca:Cu=1.8:0.4:2:2:3.2); the sample was then coated on an Ag (or MgO) substrate with a brush; after being dried at 105{degree}C for one hour, it was thermally decomposed at 700{degree}C for one hour; then, the process of prissurized forming (at pressure 2 to 5 ton f/cm{sup 2}) and of sintering at 845{degree}C for 20 hours or more were performed on the sample to form a thick film sample. A critical temperature Tc, critical current density Jc, etc., were measured on such thick film sample. As a result, nearly same values were obtained as Tc (93K) and Jc (84A/cm{sup 2}) which were those of a bulk sample made by using the same powder sample, pressurizing at 2 ton f/cm{sup 2} for pelletizing, and sintering at 845{degree}C for 20 hours. 6 refs., 7 figs., 1 tab.
Interplay of CDW, SDW and superconductivity in high-Tc cuprates

International Nuclear Information System (INIS)

Panda, S.K.; Rout, G.C.

2009-01-01

We present a model calculation of the interplay of the charge density wave (CDW), spin density wave (SDW) and superconductivity in high temperature superconductors. In low doping situation the long range antiferromagnetic order is destroyed to give rise to SDW state accompanied by a CDW state in the system due to doping. For suitable doping the superconductivity appears in the system. The CDW state may describe the pseudogap phenomenon which co-exists with the superconducting phase and extends to normal phase in high-T c systems. These three competiting interactions co-exist together. These three gap parameters are calculated from the model Hamiltonian and solved self-consistently. By varying their coupling constants their interplay are investigated. Finally density of states is calculated for the conduction band which displays the experimental conductance data of Ekino et al. [T. Ekino, Y. Sezaki, H. Fujji, Phys. Rev. B 60 (1999) 6916].
Effect of localized electron states on superconductivity of ultrathin beryllium films

International Nuclear Information System (INIS)

Tutov, V.I.; Semenenko, E.E.

1988-01-01

A wide spectrum of distortions is induced in ultrathin beryllium films of thickness less than 10 A, which are responsible for the system transition from the strong localization state completely suppressing superconductivity (in this case R □ of the layer reaches 97600 Ohm) to the weak localization stae coexisting with superconductivity at comparatively high T c (5 K). The resistance per square R □ of the films decreases more than by an order of magnitude. The superconductivity with T c =1.7 K occurs at rather strong localization, when R □ of the layer is 34000 Ohm
High temperature superconductivity the road to higher critical temperature

CERN Document Server

Uchida, Shin-ichi

2015-01-01

This book presents an overview of material-specific factors that influence Tc and give rise to diverse Tc values for copper oxides and iron-based high- Tc superconductors on the basis of more than 25 years of experimental data, to most of which the author has made important contributions. The book then explains why both compounds are distinct from others with similar crystal structure and whether or not one can enhance Tc, which in turn gives a hint on the unresolved pairing mechanism. This is an unprecedented new approach to the problem of high-temperature superconductivity and thus will be inspiring to both specialists and non-specialists interested in this field. Readers will receive in-depth information on the past, present, and future of high-temperature superconductors, along with special, updated information on what the real highest Tc values are and particularly on the possibility of enhancing Tc for each member material, which is important for application. At this time, the highest Tc has not been...
Evolution of superconducting properties with disorder in epitaxial NbN films

International Nuclear Information System (INIS)

Chockalingam, S P; Chand, Madhavi; Jesudasan, John; Raychaudhuri, Pratap; Tripathi, Vikram

2009-01-01

NbN is a conventional BCS superconductor in which disorder can be tuned from moderately clean limit to dirty limit without affecting its epitaxial nature. We studied the superconducting properties of epitaxial NbN films of different disorder characterized by k F l ranging from 8.77 to 2.56 through the transport measurements. Using reactive magnetron sputtering NbN films of different disorder are deposited by varying the sputtering power and amount of N 2 in Ar:N 2 mixture of sputtering gas. The disorder parameter k F l is obtained from the carrier density (n) and the resistivity (ρ) of the films. NbN films with higher disorder have lower transition temperature (T c ) and larger resistivity which decreases with decreasing disorder. The carrier density determined from Hall measurements show that highly disordered films have lower carrier density and vice versa. Our studies show that NbN is a good system to investigate the effects of disorder on superconductivity where the superconducting properties evolve with the disorder in thin films.
Thickness dependence of J_c (0) in MgB_2 films

International Nuclear Information System (INIS)

Chen, Yiling; Yang, Can; Jia, Chunyan; Feng, Qingrong; Gan, Zizhao

2016-01-01

Highlights: • A serial of MgB_2 superconducting films from 10 nm to 8 µm have been prepared. • T_c and J_c (5 K, 0 T) of films are high. • J_c (5 K, 0 T) reaches its maximum 2.3 × 10"8 A cm"−"2 for 100 nm films. • The relationship between thickness and J_c has been discussed in detail. - Abstract: MgB_2 superconducting films, whose thicknesses range from 10 nm to 8 µm, have been fabricated on SiC substrates by hybrid physical–chemical vapor deposition (HPCVD) method. It is the first time that the T_c and the J_c of MgB_2 films are studied on such a large scale. It is found that with the increasing of thickness, T_c elevates first and then keeps roughly stable except for some slight fluctuations, while J_c (5 K, 0 T) experiences a sharp increase followed by a relatively slow fall. The maximum J_c (5 K, 0 T) = 2.3 × 10"8 A cm"−"2 is obtained for 100 nm films, which is the experimental evidence for preparing high-quality MgB_2 films by HPCVD method. Thus, this work may provide guidance on choosing the suitable thickness for applications. Meanwhile, the films prepared by us cover ultrathin films, thin films and thick films, so the study on them will bring a comprehensive understanding of MgB_2 films.
Magnetic-Field-Tunable Superconducting Rectifier

Science.gov (United States)

Sadleir, John E.

2009-01-01

Superconducting electronic components have been developed that provide current rectification that is tunable by design and with an externally applied magnetic field to the circuit component. The superconducting material used in the device is relatively free of pinning sites with its critical current determined by a geometric energy barrier to vortex entry. The ability of the vortices to move freely inside the device means this innovation does not suffer from magnetic hysteresis effects changing the state of the superconductor. The invention requires a superconductor geometry with opposite edges along the direction of current flow. In order for the critical current asymmetry effect to occur, the device must have different vortex nucleation conditions at opposite edges. Alternative embodiments producing the necessary conditions include edges being held at different temperatures, at different local magnetic fields, with different current-injection geometries, and structural differences between opposite edges causing changes in the size of the geometric energy barrier. An edge fabricated with indentations of the order of the coherence length will significantly lower the geometric energy barrier to vortex entry, meaning vortex passage across the device at lower currents causing resistive dissipation. The existing prototype is a two-terminal device consisting of a thin-film su - perconducting strip operating at a temperature below its superconducting transition temperature (Tc). Opposite ends of the strip are connected to electrical leads made of a higher Tc superconductor. The thin-film lithographic process provides an easy means to alter edge-structures, current-injection geo - metries, and magnetic-field conditions at the edges. The edge-field conditions can be altered by using local field(s) generated from dedicated higher Tc leads or even using the device s own higher Tc superconducting leads.
Electrochemical processing of high-Tc Bi (Pb)–Sr–Ca–CuO thin films

Indian Academy of Sciences (India)

The different preparative parameters such as deposition potential, deposition time were studied and optimized. These films were then oxidized electrochemically at room temperature in an alkaline (1 N KOH) solution, and also at 600°C temperature in an oxygen atmosphere. The films showed the superconducting behaviour ...
The elastic limit of vortex movement in superconducting thin films

International Nuclear Information System (INIS)

Doyle, R.A.; Kumar, D.; Pullan, P.; Gross, R.; Campbell, A.M.; Blamire, M.G.; Somekh, R.E.; Evetts, J.E.

1993-01-01

Here we report four point ac transport FD measurements on epitaxial YBCO films and also polycrystalline NbTa films. Considerable efforts have recently been put into investigating low T c systems (11) in order to model high Tc materials in which the pinning and other properties are less easily controlled by microstructural modification and in which the parameter values are less well known. Moreover no reports exist of the FD behaviour of low T c thin film systems. In the case of the YBCO films, the results will be seen to be able to be reconciled with IP effects due to the superconducting CuO layers. In the case of the NbTa films, the results are in agreement with extrinsic pinning expected from the columnar defects (grain boundaries) observed in microstructural (SEM) studies (11). The data on all samples suggests core pinning in both (high Κ) systems. Features in the FD curves of the YBCO system when the field is carefully applied parallel to the planes occur at distances corresponding to the interlayer spacing providing direct evidence for IP. The technique also offers the possibility of investigating the frequency dependence of the effect as well as looking for curvature in the FD response below the onset of dissipation in the resistive component. The former study should be able to separate resistive from hysteretic (Bean) type losses whereas the latter might expose information about the shape of the pinning wells in addition to their sizes. These are discussed briefly here but will form the basis of further more detailed study. It will be argued that the FD technique is a powerful approach for investigation of the mixed state, allowing information to be extracted which is unavailable from other techniques. (orig.)
Full-switching FSF-type superconducting spin-triplet magnetic random access memory element

Science.gov (United States)

Lenk, D.; Morari, R.; Zdravkov, V. I.; Ullrich, A.; Khaydukov, Yu.; Obermeier, G.; Müller, C.; Sidorenko, A. S.; von Nidda, H.-A. Krug; Horn, S.; Tagirov, L. R.; Tidecks, R.

2017-11-01

In the present work a superconducting Co/CoOx/Cu41Ni59 /Nb/Cu41Ni59 nanoscale thin film heterostructure is investigated, which exhibits a superconducting transition temperature, Tc, depending on the history of magnetic field applied parallel to the film plane. In more detail, around zero applied field, Tc is lower when the field is changed from negative to positive polarity (with respect to the cooling field), compared to the opposite case. We interpret this finding as the result of the generation of the odd-in-frequency triplet component of superconductivity arising at noncollinear orientation of the magnetizations in the Cu41Ni59 layer adjacent to the CoOx layer. This interpretation is supported by superconducting quantum interference device magnetometry, which revealed a correlation between details of the magnetic structure and the observed superconducting spin-valve effects. Readout of information is possible at zero applied field and, thus, no permanent field is required to stabilize both states. Consequently, this system represents a superconducting magnetic random access memory element for superconducting electronics. By applying increased transport currents, the system can be driven to the full switching mode between the completely superconducting and the normal state.
Comparison of water degradation of YBaCuO superconducting films made from different structures

International Nuclear Information System (INIS)

Chang, C.; Tsai, J.A.

1988-01-01

Immersion of YBaCuO superconducting films in water has shown a large difference in degradation between structures with and without silver. For the structures containing silver layers and depositing at a high temperature, superconducting films with zero resistance at 87 K remain superconductive at 77 K after 5 h immersion in water, with an increase in room-temperature film resistance by a factor of 4; the contact resistance remains low after 60 h of immersion, allowing the measurement at low temperatures. For the structures containing no silver and depositing at room temperature, the contact resistance rapidly increases with immersion times, making the measurement at 77 K difficult after 5 min of immersion. Changes in the sharpness of the superconductive transition, and structures of the films due to the water immersion are also compared
Superconductivity of high Tc Scientific revolution?; Superconductividad de alta Tc una revolucion cientifica?

Energy Technology Data Exchange (ETDEWEB)

Marquina, J E; Ridaura, R; Gomez, R; Marquina, V; Alvarez, J L

1998-12-31

A short history of superconductivity, since its discovery by Bednorz and Muller to the development of new materials with high transition temperatures, is presented. Further evolvements are analyzed in terms of T.s. Kuhn conceptions expressed in his book. The Structure of Scientific Revolutions. (Author) 4 refs.
YBa2Cu3O(7-x) based superconducting thin films by multitarget sputtering

International Nuclear Information System (INIS)

Bouteloup, E.; Mercey, B.; Poullain, G.; Brousse, T.; Murray, H.; Raveau, B.

1990-01-01

This paper reports a new technique to prepare superconducting YBa 2 Cu 3 O (7-x) thin films. The multitarget sputtering apparatus described below allows the simultaneous and reproducible production of numerous films with a metallic composition close to Y 17% Ba 33% Cu 50% . Superconducting films (R = 0) at 80 K have been produced on polycrystalline zirconia substrates after a high temperature annealing [fr
Mechanochemical effects on high-Tc superconductor powders

International Nuclear Information System (INIS)

Yamada, Taichi; Nagai, Ryoji; Takeuchi, Manabu; Minehara, Eisuke.

1991-03-01

We have investigated the mechanochemical effects on high-Tc superconductor (YBa 2 Cu 3 O 7 -δ) powders. The powder was mechanically ground in air using an agate mortar with a pestle. The grinding time was varied from 2 to 100 min. The mean particle sizes of the powders were measured by a sedimentation method. The degradation of superconductivity was evaluated by the measurements of the crystallinity and volume fraction of the superconducting phase. The crystallinity was estimated from X-ray diffraction patterns. The volume fraction of the superconducting phase was estimated from the diamagnetization. The results of these changes of 2 min. and 100 min. grinding are respectively as follows; 1) mean particle size: 10.8 μm and 7.2 μm, 2) crystallinity: 40.0 % and 24.8 %, 3) volume fraction of superconducting phase: 91.5 % and 30.0 %. Recovery of the crystallinity and superconductivity of the ground specimens by re-sintering and re-annealing was also studied. It was found that the recovery of both of the characteristics was not complete. (author)
Pulsed laser deposition and characterisation of thin superconducting films

Energy Technology Data Exchange (ETDEWEB)

Morone, A [CNR, zona industriale di Tito Scalo, Potenza (Italy). Istituto per i Materiali Speciali

1996-09-01

Same concepts on pulsed laser deposition of thin films will be discussed and same examples of high transition temperature (HTc) BiSrCaCuO (BISCO) and low transition temperature NbN/MgO/NbN multilayers will be presented. X-ray and others characterizations of these films will be reported and discussed. Electrical properties of superconducting thin films will be realized as a function of structural and morphological aspect.
A contribution to the study of high Tc superconducting coatings and multi-layer coatings electromagnetic properties: surface impedance measurement with a tunnel diode oscillator

International Nuclear Information System (INIS)

Omari, A.

1993-01-01

A surface impedance measurement system for conducting or superconducting thin films have been developed through the electromagnetic coupling of these films to a tunnel diode oscillator. The electromagnetic response of YBa 2 Cu 3 O 7-δ superconducting films and of id/La 2-x Sr x Cu O 4 multilayers, is studied, showing the 'granular' type of these materials. The intergranular coupling is of the SIS type for the films and of the SNS type for the multilayers. A resistance increase is observed when the temperature decreases in the superconducting phase. 120 p., 45 fig., 60 ref
Superconducting oxide thin films by ion beam sputtering

International Nuclear Information System (INIS)

Kobrin, P.H.; DeNatale, J.F.; Housley, R.M.; Flintoff, J.F.; Harker, A.B.

1987-01-01

Superconducting thin films of ternary copper oxides from the Y-Ba-Cu-O and La-Sr-Cu-O systems have been deposited by ion beam sputtering of ceramic targets. Crystallographic orientation of the polycrystalline films has been shown to vary with substrate identity, deposition temperature and annealing temperature. The onset of the superconductive transition occurs near 90K in the Y-Ba-Cu-O system. Fe impurities of < 0.2% have been found to inhibit the superconducting transition, probably by migrating to the grain boundaries
Noise and conversion performance of a high-Tc superconducting Josephson junction mixer at 0.6 THz

Science.gov (United States)

Gao, Xiang; Du, Jia; Zhang, Ting; Guo, Yingjie Jay

2017-11-01

This letter presents both theoretical and experimental investigations on the noise and conversion performance of a high-Tc superconducting (HTS) step-edge Josephson-junction mixer at the frequency of 0.6 THz and operating temperatures of 20-40 K. Based on the Y-factor and U-factor methods, a double-sideband noise temperature of around 1000 K and a conversion gain of -3.5 dB were experimentally obtained at 20 K. At the temperature of 40 K, the measured mixer noise and conversion efficiency are around 2100 K and -10 dB, respectively. The experimental data are in good agreement with the numerical analysis results using the three-port model. A detailed performance comparison with other reported HTS terahertz mixers has confirmed the superior performance of our presented mixer device.
Deposition of superconducting (Cu, C)-Ba-O films by pulsed laser deposition at moderate temperature

International Nuclear Information System (INIS)

Yamamoto, Tetsuro; Kikunaga, Kazuya; Obara, Kozo; Terada, Norio; Kikuchi, Naoto; Tanaka, Yasumoto; Tokiwa, Kazuyasu; Watanabe, Tsuneo; Sundaresan, Athinarayanan; Shipra

2007-01-01

Superconducting (Cu, C)-Ba-O thin films have been epitaxially grown on (100) SrTiO 3 at a low growth temperature of 500-600 deg. C by pulsed laser deposition. The dependences of their crystallinity and transport properties on preparation conditions have been investigated in order to clarify the dominant parameters for carbon incorporation and the emergence of superconductivity. It has been revealed that the CO 3 content in the films increases with increasing both the parameters of partial pressure of CO 2 during film growth and those of growth rate and enhancement of superconducting properties. The present study has also revealed that the structural and superconducting properties of the (Cu, C)-Ba-O films are seriously deteriorated by the irradiation of energetic particles during deposition. Suppression of the radiation damage is another key for a high and uniform superconducting transition. By these optimizations, a superconducting onset temperature above 50 K and a zero-resistance temperature above 40 K have been realized

Rapid solidification for preparation of high Tc superconductors

International Nuclear Information System (INIS)

Yavari, A.R.

1988-01-01

High Tc superconducting oxides are prepared in two different ways using rapid solidification: by oxidation of microcrystalline or amorphous tapes obtained by quenching the liquid alloy and via crystallisation of the amorphous oxide obtained by rapid quenching of the oxide melt. This technique is applied for the first time to the BiCaSrCuO family [fr
SHMUTZ & PROTON-DIAMANT H + Irradiated/Written-Hyper/Super-conductivity(HC/SC) Precognizance/Early Experiments Connections: Wet-Graphite Room-Tc & Actualized MgB2 High-Tc: Connection to Mechanical Bulk-Moduli/Hardness: Diamond Hydrocarbon-Filaments, Disorder, Nano-Powders:C,Bi,TiB2,TiC

Science.gov (United States)

Wunderman, Irwin; Siegel, Edward Carl-Ludwig; Lewis, Thomas; Young, Frederic; Smith, Adolph; Dresschhoff-Zeller, Gieselle

2013-03-01

SHMUTZ: ``wet-graphite''Scheike-....[Adv.Mtls.(7/16/12)]hyper/super-SCHMUTZ-conductor(S!!!) = ``wet''(?)-``graphite''(?) = ``graphene''(?) = water(?) = hydrogen(?) =ultra-heavy proton-bands(???) = ...(???) claimed room/high-Tc/high-Jc superconductOR ``p''-``wave''/ BAND(!!!) superconductIVITY and actualized/ instantiated MgB2 high-Tc superconductors and their BCS- superconductivity: Tc Siegel[ICMAO(77);JMMM 7,190(78)] connection to SiegelJ.Nonxline-Sol.40,453(80)] disorder/amorphous-superconductivity in nano-powders mechanical bulk/shear(?)-moduli/hardness: proton-irradiated diamond, powders TiB2, TiC,{Siegel[Semis. & Insuls.5:39,47, 62 (79)])-...``VS''/concommitance with Siegel[Phys.Stat.Sol.(a)11,45(72)]-Dempsey [Phil.Mag. 8,86,285(63)]-Overhauser-(Little!!!)-Seitz-Smith-Zeller-Dreschoff-Antonoff-Young-...proton-``irradiated''/ implanted/ thermalized-in-(optimal: BOTH heat-capacity/heat-sink & insulator/maximal dielectric-constant) diamond: ``VS'' ``hambergite-borate-mineral transformable to Overhauser optimal-high-Tc-LiBD2 in Overhauser-(NW-periodic-table)-Land: CO2/CH4-ETERNAL-sequestration by-product: WATER!!!: physics lessons from
Review of thin film superconductivity

International Nuclear Information System (INIS)

Kihlstrom, K.E.

1989-01-01

Advances in thin film superconductivity are critical to the success of many proposed applications. The authors review several of the prominent techniques currently used to produce thin films of the high temperature superconductors including electron beam co-deposition, sputtering (both multiple and composite source configurations) and laser ablation. The authors look at the relevant parameters for each and evaluate the advantages and disadvantages of each technique. In addition, promising work on in situ oxidation is discussed. Also addressed are efforts to find optimum substrate materials and substrate buffer layers for various applications. The current state of the art for T c , J c and H c2 is presented for the yttrium, bismuth, and thallium compounds
Thin Film Approaches to the SRF Cavity Problem Fabrication and Characterization of Superconducting Thin Films

Energy Technology Data Exchange (ETDEWEB)

Beringer, Douglas [College of William and Mary, Williamsburg, VA (United States)

2017-08-01

Superconducting Radio Frequency (SRF) cavities are responsible for the acceleration of charged particles to relativistic velocities in most modern linear accelerators, such as those employed at high-energy research facilities like Thomas Jefferson National Laboratory’s CEBAF and the LHC at CERN. Recognizing SRF as primarily a surface phenomenon enables the possibility of applying thin films to the interior surface of SRF cavities, opening a formidable tool chest of opportunities by combining and designing materials that offer greater performance benefit. Thus, while improvements in radio frequency cavity design and refinements in cavity processing techniques have improved accelerator performance and efficiency – 1.5 GHz bulk niobium SRF cavities have achieved accelerating gradients in excess of 35 MV/m – there exist fundamental material bounds in bulk superconductors limiting the maximally sustained accelerating field gradient (≈ 45 MV/m for Nb) where inevitable thermodynamic breakdown occurs. With state of the art Nb based cavity design fast approaching these theoretical limits, novel material innovations must be sought in order to realize next generation SRF cavities. One proposed method to improve SRF performance is to utilize thin film superconducting-insulating-superconducting (SIS) multilayer structures to effectively magnetically screen a bulk superconducting layer such that it can operate at higher field gradients before suffering critically detrimental SRF losses. This dissertation focuses on the production and characterization of thin film superconductors for such SIS layers for radio frequency applications. Correlated studies on structure, surface morphology and superconducting properties of epitaxial Nb and MgB2 thin films are presented.
Hall effect of K-doped superconducting thin films

Energy Technology Data Exchange (ETDEWEB)

Son, Eunseon; Lee, Nam Hoon; Kang, Won Nam [Dept. of physics, Sungkyunkwan University, Suwon (Korea, Republic of); Hwang, Tae Jong; Kim, Dong Ho [Dept. of physics, Yeungnam University, Gyeongsan(Korea, Republic of)

2013-09-15

We have studied Hall effect for potassium (K)-doped BaFe{sub 2}As{sub 2}superconducting thin films by analyzing the relation between the longitudinal resistivity (ρ{sub xy}) and the Hall resistivity (ρ{sub xy}). The thin films used in this study were fabricated on Al{sub O3} (000l) substrates by using an ex-situ pulsed laser deposition (PLD) technique under a high-vacuum condition of ∼10{sup -6} Torr. The samples showed the high superconducting transition temperatures (T{sub C}) of ∼40 K. The ρ{sub xx} and ρ{sub xy}the for K-doped BaFeAs{sub 2} thin films were measured by using a physical property measurement system (PPMS) with a temperature sweep (T-sweep) mode at an applied current density of 100 A/cm{sup 2} and at magnetic fields from 0 up to 9 T. We report the T-sweep results of the ρ{sub xx} and the ρ{sub xy} to investigate Hall scaling behavior on the basis of the relation of ρ{sub xy} = A(ρ{sub xy}){sup β}. The ρ{sub xx} values are 3.0 ± 0.2 in the c-axis-oriented K-doped BaFeAs{sub 2} thin films, whereas the thin films with various oriented-directions like a polycrystal showed slightly lower β than that of c-axis-oriented thin films. Interestingly, the β value is decreased with increasing magnetic fields.
High temperature interface superconductivity

International Nuclear Information System (INIS)

Gozar, A.; Bozovic, I.

2016-01-01

Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T_c superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T_c Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.
Infrared refractive index of thin YBa2Cu3O7 superconducting films

International Nuclear Information System (INIS)

Zhang, Z.M.; Choi, B.I.; Le, T.A.; Flik, M.I.; Siegal, M.P.; Phillips, J.M.

1992-01-01

This work investigates whether thin-film optics with a constant refractive index can be applied to high-T c superconducting thin films. The reflectance and transmittance of YBa 2 Cu 3 O 7 films on LaAlO 3 substrates are measured using a Fourier-transform infrared spectrometer at wavelengths from 1 to 100 μm at room temperature. The reflectance of these superconducting films at 10K in the wavelength region from 2.5 to 25 μm is measured using a cryogenic reflectance accessory. The film thickness varies from 10 to 200 nm. By modeling the frequency-dependent complex conductivity in the normal and superconducting states and applying electromagnetic-wave theory, the complex refractive index of YBa 2 Cu 3 O 7 films is obtained with a fitting technique. It is found that a thickness-independent refractive index can be applied even to a 25nm film, and average values of the spectral refractive index for film thicknesses between 25 and 200 nm are recommended for engineering applications
Fabrication and characterizations of high-Tc superconducting ceramic/polymer 0--3 composites

International Nuclear Information System (INIS)

Du, J.; Unsworth, J.

1994-01-01

High-T c superconducting ceramic YBa 2 Cu 3 O 7-x /thermosetting plastic 0--3 composites were fabricated. The structure, physical property, magnetic susceptibility, levitation, and mechanical strength of the composites were accessed. The influence of filler content on these properties was also studied. Although the 0--3 composites lack an electrical superconducting path through materials, the intrinsic diamagnetic properties were preserved. The magnetic superconducting transition temperature was not degraded. The values of magnetic susceptibility and levitation force for the composites were basically proportional to the actual volume fraction of superconducting filler. These new composite materials are most suitable for the applications in levitating vehicles and mechanical bearings
Uniaxial strain orientation dependence of superconducting transition temperature (Tc) and critical superconducting pressure (Pc) in β-(BDA-TTP)2I3.

Science.gov (United States)

Kikuchi, Koichi; Isono, Takayuki; Kojima, Masayuki; Yoshimoto, Haruo; Kodama, Takeshi; Fujita, Wataru; Yokogawa, Keiichi; Yoshino, Harukazu; Murata, Keizo; Kaihatsu, Takayuki; Akutsu, Hiroki; Yamada, Jun-ichi

2011-12-14

Dependence of the superconducting transition temperature (T(c)) and critial superconducting pressure (P(c)) of the pressure-induced superconductor β-(BDA-TTP)(2)I(3) [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] on the orientation of uniaxial strain has been investigated. On the basis of the overlap between the upper and lower bands in the energy dispersion curve, the pressure orientation is thought to change the half-filled band to the quarter-filled one. The observed variations in T(c) and P(c) are explained by considering the degree of application of the pressure and the degree of contribution of the effective electronic correlation at uniaxial strains with different orientations parallel to the conducting donor layer. © 2011 American Chemical Society
High-Q Tl2CaBa2Cu2O8 high-Tc superconducting quasi-optical millimeter-wave bandpass filters working at 77 K

International Nuclear Information System (INIS)

Zhang, D.; Fetterman, H.R.

1994-01-01

Tl 2 CaBa 2 Cu 2 O 8 high-temperature superconducting thin films with T c 's of over 100 K on LaAlO 3 substrates were used to fabricate quasi-optical millimeter-wave bandpass filters. Q-factors of over 400 were achieved, at liquid nitrogen temperatures from these filters at W-band frequencies (75--110 GHz)
Switching, storage, and erasure effects in a superconducting thin film

International Nuclear Information System (INIS)

Testardi, L.R.

1976-01-01

Thin niobium films can be switched from a superconducting to a resistive state permanently by application of a short electrical pulse. Application of a short pulse of opposite polarity returns the film to the superconducting state
Superconducting Properties of Lead-Bismuth Films Controlled by Ferromagnetic Nanowire Arrays

Science.gov (United States)

Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.

2011-03-01

Superconducting properties of lead-bismuth (82% Pb and 18% Bi) alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb 82 Bi 18 films are then quench-condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb 82 Bi 18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and the material variety was observed.
Superconducting films of YBaCuO

International Nuclear Information System (INIS)

Coelho, A.L.

1991-01-01

Thick films of YBa 2 Cu 3 O 7 - x have been prepared on alumina and YSZ (Yttria-stabilized zirconia) substrates by the screen printing technique. Several experimental conditions have been studied, for instance: sintering time, temperature, thickness and atmosphere annealed. The resulting films have been characterized by X-ray diffraction, AC electrical resistance, AC susceptibility and scanning electron microscopy. The surface and cross-section have been observed with an optical microscope. The X-ray diffraction patterns have been compared with a typical pattern and that has indicated the good quality of the samples. AC resistance and its temperature dependence have been measured in the standard four-probe configuration. Films thickness has been estimated in the scanning electron microscope. This technique has been suitable for production of high T c superconducting films being a simple and inexpensive method. (author)
High-Tc superconductivity in the d-p electron system

International Nuclear Information System (INIS)

Ivanov, V.A.; Zaitsev, R.A.

1991-01-01

The relaxation time with spin flip τ s and the parameters ξ, δ, χ of superconducting phase have been calculated on the basis of the kinematical mechanism of superconductivity in strongly correlated oxide models. An inter-relation between the superconducting gap Δ o and the specific heat jump Δ c allowing the experimental verification was obtained and the Ginsburg-Landau equation derived. (author). 8 refs., 2 figs
Impurity band Mott insulators: a new route to high Tc superconductivity

Directory of Open Access Journals (Sweden)

Ganapathy Baskaran

2008-01-01

Full Text Available Last century witnessed the birth of semiconductor electronics and nanotechnology. The physics behind these revolutionary developments is certain quantum mechanical behaviour of 'impurity state electrons' in crystalline 'band insulators', such as Si, Ge, GaAs and GaN, arising from intentionally added (doped impurities. The present article proposes that certain collective quantum behaviour of these impurity state electrons, arising from Coulomb repulsions, could lead to superconductivity in a parent band insulator, in a way not suspected before. Impurity band resonating valence bond theory of superconductivity in boron doped diamond, recently proposed by us, suggests possibility of superconductivity emerging from impurity band Mott insulators. We use certain key ideas and insights from the field of high-temperature superconductivity in cuprates and organics. Our suggestion also offers new possibilities in the field of semiconductor electronics and nanotechnology. The current level of sophistication in solid state technology and combinatorial materials science is very well capable of realizing our proposal and discover new superconductors.
Slip processing of high Tc superconductors

International Nuclear Information System (INIS)

Sinha, R.K.; Sinha, R.K.

1991-01-01

Slip-processing technique has been used to fabricate tapes and alumina-supported films of superconducting YBa 2 Cu 3 Osub(7-x). Good densification and connectivity are revealed by scanning electron microscopy. Both the tape and film show superconductivity well above the liquid nitrogen temperature with a transition range of 3deg and 5degK respectively. (author). 10 refs., 4 figs
Application of High-Temperature Superconducting Thin-Film Devices to Electro-Optical and Electronic Warfare Systems

Science.gov (United States)

1990-02-01

superconducting dispersive (chirp) delay line. Bt currents (IB 1 and 1B 2) control states of write junctions (gates 1 and 2). (Counter) clockwise currents...Gavaler, and "S. A. Reihle, "Superconductive Convolver with June- A. I. Braginski, "Optical Response of Epitaxial Films tion Ring Nlixers," IELT Trans
Interface-Induced Zeeman-Protected Superconductivity in Ultrathin Crystalline Lead Films

Science.gov (United States)

Liu, Yi; Wang, Ziqiao; Zhang, Xuefeng; Liu, Chaofei; Liu, Yongjie; Zhou, Zhimou; Wang, Junfeng; Wang, Qingyan; Liu, Yanzhao; Xi, Chuanying; Tian, Mingliang; Liu, Haiwen; Feng, Ji; Xie, X. C.; Wang, Jian

2018-04-01

Two-dimensional (2D) superconducting systems are of great importance for exploring exotic quantum physics. The recent development of fabrication techniques has stimulated studies of high-quality single-crystalline 2D superconductors, where intrinsic properties give rise to unprecedented physical phenomena. Here, we report the observation of Zeeman-type spin-orbit interaction protected superconductivity (Zeeman-protected superconductivity) in 4-monolayer (ML) to 6-ML crystalline Pb films grown on striped incommensurate Pb layers on Si(111) substrates by molecular beam epitaxy. An anomalously large in-plane critical field far beyond the Pauli limit is detected, which can be attributed to the Zeeman-protected superconductivity due to the in-plane inversion symmetry breaking at the interface. Our work demonstrates that, in superconducting heterostructures, the interface can induce Zeeman-type spin-orbit interactions and modulate the superconductivity.
Degradation of superconducting Nb/NbN films by atmospheric oxidation

Energy Technology Data Exchange (ETDEWEB)

Henry, Michael David; Wolfley, Steven L.; Young, Travis Ryan; Monson, Todd; Pearce, Charles Joseph; Lewis, Rupert M.; Clark, Blythe; Brunke, Lyle Brent; Missert, Nancy A.

2017-03-01

Niobium and niobium nitride thin films are transitioning from fundamental research toward wafer scale manufacturing with technology drivers that include superconducting circuits and electronics, optical single photon detectors, logic, and memory. Successful microfabrication requires precise control over the properties of sputtered superconducting films, including oxidation. Previous work has demonstrated the mechanism in oxidation of Nb and how film structure could have deleterious effects upon the superconducting properties. This study provides an examination of atmospheric oxidation of NbN films. By examination of the room temperature sheet resistance of NbN bulk oxidation was identified and confirmed by secondary ion mass spectrometry. As a result, Meissner magnetic measurements confirmed the bulk oxidation not observed with simple cryogenic resistivity measurements.
Dependence of the quasiparticle recombination rate on the superconducting gap and TC

Science.gov (United States)

Carr, G. L.; Xi, Xiaoxiang; Hwang, J.; Tashiro, H.; Reitze, D. H.; Tanner, D. B.

2010-03-01

The relaxation of excess quasiparticles in a BCS superconductor is known to depend on quantities such as the quasiparticle & phonon density of states, and their coupling (Kaplan et al, Phys. Rev. B 14 4854, 1976). Disorder or an applied field can disrupt superconductivity, as evidenced by a reduced TC. We consider some simple modifications to the quasiparticle density of states consistent with a suppressed energy gap and TC, leading to changes in the intrinsic and effective (measured) rates for excess quasiparticles to recombine into pairs. We review some results for disordered MoGe and discuss the magnetic-field dependence of the recombination process.

Korea's developmental program for superconductivity

Science.gov (United States)

Hong, Gye-Won; Won, Dong-Yeon; Kuk, Il-Hyun; Park, Jong-Chul

1995-04-01

Superconductivity research in Korea was firstly carried out in the late 70's by a research group in Seoul National University (SNU), who fabricated a small scale superconducting magnetic energy storage system under the financial support from Korea Electric Power Company (KEPCO). But a few researchers were involved in superconductivity research until the oxide high Tc superconductor was discovered by Bednorz and Mueller. After the discovery of YBaCuO superconductor operating above the boiling point of liquid nitrogen (77 K)(exp 2), Korean Ministry of Science and Technology (MOST) sponsored a special fund for the high Tc superconductivity research to universities and national research institutes by recognizing its importance. Scientists engaged in this project organized 'High Temperature Superconductivity Research Association (HITSRA)' for effective conducting of research. Its major functions are to coordinate research activities on high Tc superconductivity and organize the workshop for active exchange of information. During last seven years the major superconductivity research has been carried out through the coordination of HITSRA. The major parts of the Korea's superconductivity research program were related to high temperature superconductor and only a few groups were carrying out research on conventional superconductor technology, and Korea Atomic Energy Research Institute (KAERI) and Korea Electrotechnology Research Institute (KERI) have led this research. In this talk, the current status and future plans of superconductivity research in Korea will be reviewed based on the results presented in interim meeting of HITSRA, April 1-2, 1994. Taejeon, as well as the research activity of KAERI.
Interface-Induced Zeeman-Protected Superconductivity in Ultrathin Crystalline Lead Films

Directory of Open Access Journals (Sweden)

Yi Liu

2018-04-01

Full Text Available Two-dimensional (2D superconducting systems are of great importance for exploring exotic quantum physics. The recent development of fabrication techniques has stimulated studies of high-quality single-crystalline 2D superconductors, where intrinsic properties give rise to unprecedented physical phenomena. Here, we report the observation of Zeeman-type spin-orbit interaction protected superconductivity (Zeeman-protected superconductivity in 4-monolayer (ML to 6-ML crystalline Pb films grown on striped incommensurate Pb layers on Si(111 substrates by molecular beam epitaxy. An anomalously large in-plane critical field far beyond the Pauli limit is detected, which can be attributed to the Zeeman-protected superconductivity due to the in-plane inversion symmetry breaking at the interface. Our work demonstrates that, in superconducting heterostructures, the interface can induce Zeeman-type spin-orbit interactions and modulate the superconductivity.
Bi-Sr-Ca-Cu-O superconducting thin films: theory and experiment

Energy Technology Data Exchange (ETDEWEB)

Yavuz, M [Department of Mechanical Engineering and Mechatronics Engineering Program, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Boybay, M S [Department of Mechanical Engineering and Mechatronics Engineering Program, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Elbuken, C [Department of Mechanical Engineering and Mechatronics Engineering Program, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Andrews, M J [Los Alamos National Lab, PO Box 1663, Mail Stop B 296, Los Alamos, NM 87545 (United States); Hu, C R [Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Ross, J H [Department of Physics, Texas A and M University, College Station, Texas 77843 (United States)

2006-06-01

The interest of this paper centers on fabrication and characterization and modeling of vortices in high temperature superconducting thin films. As a first step, the magnetic vertices of the superconducting matrix were modeled. As a second, Bi-Sr-Ca-Cu-O thin films were grown using Pulsed Laser Ablation (PLD) on single crystal MgO substrates as magnetic templates for the potential use for Nano and Microelectronic circuits, and were characterized by x-ray diffraction, electron, and atomic force microscopy. The third step (future work) will be observation and pinning of these vortices using Bitter decoration.
Spray pyrolysis process for preparing superconductive films

International Nuclear Information System (INIS)

Hsu, H.M.; Yee, I.Y.

1991-01-01

This paper describes a spray pyrolysis method for preparing thin superconductive film. It comprises: preparing a spray pyrolysis solution comprising Bi,Sr,Ca and Cu metals in a solvent; heating a substrate to a first temperature; spraying the solution onto the heated substrate to form a film thereon; heating the film and substrate to a second temperature of about 700 degrees-825 degrees C, the second temperature being higher than the first temperature; heating the film and substrate to a third temperature of about 870 degrees-890 degrees C to melt the film; once the film and substrate reach the third temperature, further heat treating the film and substrate; cooling the film and substrate to ambient temperature. This patent also describes a spray pyrolysis method for preparing thin superconductive films. It comprises: preparing a spray pyrolysis solution comprising Bi, Ca and Cu metals and fluxing agent in a solvent; heating a substrate to a first temperature; spraying the solution onto the heated substrate to form a film thereon; heating the film and substrate to a second temperature about 700 degrees-825 degrees C, the second temperature being higher than the first temperature; heating the film and substrate at a third temperature about 840 degrees-860 degrees C; and cooling the film and substrate to ambient temperature
Studies of the Superconducting Transition in the Mo/Au-Bilayer Thin Films

Science.gov (United States)

Sadleir, John; Smith, Stephen; Iyomoto, naoko; Bandler, Simon; Chervenak, Jay; Brown, Ari; Brekowsky, Regis; Kilbourne, Caroline; Robinson, Ian

2007-01-01

At NASA Goddard, microcalorimeter arrays using superconducting transition edge sensor thermometers (TESs) are under development for high energy resolution X-ray astrophysics applications. We report on our studies of the superconducting transition in our Mo/Au-bilayer TES films including: low current measurements of the superconducting bilayer's resistance transition versus temperature on pixels with different normal metal absorber attachment designs and measured temperature scaling of the critical current and critical magnetic field.
Thin Film Approaches to the SRF Cavity Problem: Fabrication and Characterization of Superconducting Thin Films

Science.gov (United States)

Beringer, Douglas B.

Superconducting Radio Frequency (SRF) cavities are responsible for the acceleration of charged particles to relativistic velocities in most modern linear accelerators, such as those employed at high-energy research facilities like Thomas Jefferson National Laboratory's CEBAF and the LHC at CERN. Recognizing SRF as primarily a surface phenomenon enables the possibility of applying thin films to the interior surface of SRF cavities, opening a formidable tool chest of opportunities by combining and designing materials that offer greater benefit. Thus, while improvements in radio frequency cavity design and refinements in cavity processing techniques have improved accelerator performance and efficiency - 1.5 GHz bulk niobium SRF cavities have achieved accelerating gradients in excess of 35 MV/m - there exist fundamental material bounds in bulk superconductors limiting the maximally sustained accelerating field gradient (approximately 45 MV/m for Niobium) where inevitable thermodynamic breakdown occurs. With state of the art niobium based cavity design fast approaching these theoretical limits, novel material innovations must be sought in order to realize next generation SRF cavities. One proposed method to improve SRF performance is to utilize thin film superconducting-insulating-superconducting (SIS) multilayer structures to effectively magnetically screen a bulk superconducting layer such that it can operate at higher field gradients before suffering critically detrimental SRF losses. This dissertation focuses on the production and characterization of thin film superconductors for such SIS layers for radio-frequency applications.
Superconductivity: materials and applications

International Nuclear Information System (INIS)

Duchateau, J.L.; Kircher, F.; Leveque, J.; Tixador, P.

2008-01-01

This digest paper presents the different types of superconducting materials: 1 - the low-TC superconductors: the multi-filament composite as elementary constituent, the world production of NbTi, the superconducting cables of the LHC collider and of the ITER tokamak; 2 - the high-TC superconductors: BiSrCaCuO (PIT 1G) ribbons and wires, deposited coatings; 3 - application to particle physics: the the LHC collider of the CERN, the LHC detectors; 4 - applications to thermonuclear fusion: Tore Supra and ITER tokamaks; 5 - NMR imaging: properties of superconducting magnets; 6 - applications in electrotechnics: cables, motors and alternators, current limiters, transformers, superconducting energy storage systems (SMES). (J.S.)
State of the art and trends of high-Tc superconductivity

International Nuclear Information System (INIS)

Barone, A.

1990-01-01

In this paper a brief account is given on some aspects of the development of high-T c Superconductivity since the last edition of the SATT Conference. This year significant results have been obtained in the challenging endeavor of increasing high critical current densities and in the context of high-T c junctions. The attention is confined to achievements and perspectives in these two topics
Application of a phenomenological model for the surface impedance in high temperature superconducting films

International Nuclear Information System (INIS)

Mosquera, A.S.; Landinez Tellez, D.A.; Roa-Rojas, J.

2007-01-01

We report the application of a phenomenological model for the microwave surface impedance in high temperature superconducting films. This model is based on the modified two-fluid model, in which the real and imaginary parts of the surface impedance use the modelling parameter γ. This is responsible for the superconducting and normal charge carrier density and is used for the description of the temperature dependence of the London penetration depth λ L (T) including λ L (0). The relaxation time model also uses the γ parameter in combination with the residual resistance parameter α. The parameter δ 1 1 , γ, α, and δ 2 . The parameter δ 2 n (T) is a result of the competition between the increase of the relaxation time and the decrease of the normal charge-carrier density. We applied this model to analyze experimental results of MgB 2 , YBa 2 Cu 3 O 7-δ and GdBa 2 Cu 3 O 7-δ superconducting material. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Geometrical resonance effects in thin superconducting films

International Nuclear Information System (INIS)

Nedellec, P.

1977-01-01

Electron tunneling density of states measurements on thick and clear superconducting films (S 1 ) backed by films in the normal or superconducting state (S 2 ) show geometrical resonance effects associated with the spatial variation of Δ(x), the pair potential, near the interface S 1 -S 2 . The present understanding of this so-called 'Tomasch effect' is described. The dispersion relation and the nature of excitations in the superconducting state are introduced. It is shown that the introduction of Green functions give a general description of the superconducting state. The notion of Andreev scattering at the S 1 -S 2 interface is presented and connect the geometrical resonance effects to interference process between excitations. The different physical parameters involved are defined and used in the discussion of some experimental results: the variation of the period in energy with the superconducting thickness is connected to the renormalized group velocity of excitations traveling perpendicular to the film. The role of the barrier potential at the interface on the Tomasch effect is described. The main results discussed are: the decrease of the amplitude of the Tomasch structures with energy is due to the loss of the mixed electron-hole character of the superconducting excitations far away from the Fermi level; the variation of the pair potential at the interface is directly related to the amplitude of the oscillations; the tunneling selectivity is an important parameter as the amplitude as well as the phase of the oscillations are modified depending on the value of the selectivity; the phase of the Tomasch oscillations is different for an abrupt change of Δ at the interface and for a smooth variation. An ambiguity arises due to the interplay between these parameters. Finally, some experiments, which illustrate clearly the predicted effects are described [fr
Low-Cost Superconducting Wire for Wind Generators: High Performance, Low Cost Superconducting Wires and Coils for High Power Wind Generators

Energy Technology Data Exchange (ETDEWEB)

None

2012-01-01

REACT Project: The University of Houston will develop a low-cost, high-current superconducting wire that could be used in high-power wind generators. Superconducting wire currently transports 600 times more electric current than a similarly sized copper wire, but is significantly more expensive. The University of Houston’s innovation is based on engineering nanoscale defects in the superconducting film. This could quadruple the current relative to today’s superconducting wires, supporting the same amount of current using 25% of the material. This would make wind generators lighter, more powerful and more efficient. The design could result in a several-fold reduction in wire costs and enable their commercial viability of high-power wind generators for use in offshore applications.
Disappearance of superconductivity and critical resistance in thin indium films

International Nuclear Information System (INIS)

Okuma, Satoshi; Nishida, Nobuhiko

1991-01-01

In thin granular films composed of two-dimensionally coupled indium particles, we have studied influences of average particle sizes anti d on the superconducting transition. For films with anti d=280A and 224A, superconducting transition temperature stays almost constant with increasing the sheet resistance R n in the normal state, while for a film with anti d=140A, it decreases linearly with R n . This means that the system changes to a dirty superconductor by reducing anti d. With further increasing R n , superconductivity disappears when R n exceeds the value R c of order h/4e 2 , which seems to correlate with anti d. (orig.)
NbN thin films for superconducting radio frequency cavities

Science.gov (United States)

Roach, W. M.; Skuza, J. R.; Beringer, D. B.; Li, Z.; Clavero, C.; Lukaszew, R. A.

2012-12-01

NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m-1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed.
NbN thin films for superconducting radio frequency cavities

International Nuclear Information System (INIS)

Roach, W M; Clavero, C; Lukaszew, R A; Skuza, J R; Beringer, D B; Li, Z

2012-01-01

NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m −1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed. (paper)
A study on the development of high-Tc superconducting wire

International Nuclear Information System (INIS)

Won, Dong Yeon; Chang, In Soon; Lee, Jong Min; Um, Tae Yoon; Hong, Kyae Won; Lee, Ho Jin; Lee, Hee Kwun; Kim, Chan Joong; Park, Soon Dong; Kim, Woo Gon; Kim, Ki Baek; Kwon, Sun Chil

1992-10-01

On this study Y-Ba-Cu-O was prepared by partial melt process and superconducting wire was fabricated by powder-in-tube method. First, mechancial properties, electrical properties, microstructure and oxygen diffusion behavior were observed. Second, through fabricated superconducting wire, conceptual design, composition and plasticity of filament superconducting wire were investigated. (Author)
Influence of multiband sign-changing superconductivity on vortex cores and vortex pinning in stoichiometric high-Tc CaKFe4As4

Science.gov (United States)

Fente, Antón; Meier, William R.; Kong, Tai; Kogan, Vladimir G.; Bud'ko, Sergey L.; Canfield, Paul C.; Guillamón, Isabel; Suderow, Hermann

2018-04-01

We use a scanning tunneling microscope to study the superconducting density of states and vortex lattice of single crystals of CaKFe4As4 . This material has a critical temperature of Tc=35 K, one of the highest among stoichiometric iron based superconductors (FeBSCs), and is comparable to Tc found near optimal doping in other FeBSCs. We observe quasiparticle scattering from defects with a pattern related to interband scattering between zone centered hole sheets. We measure the tunneling conductance in vortex cores and find a peak due to Caroli-de Gennes-Matricon bound states. The peak is located above the Fermi level, showing that CaKFe4As4 is a clean superconductor with vortex core bound states close to the so-called extreme quantum limit. We identify locations where the superconducting order parameter is strongly suppressed due to pair breaking. Vortices are pinned at these locations, and the length scale of the suppression of the order parameter is of order of the vortex core size. As a consequence, the vortex lattice is disordered up to 8 T.
Conductus makes high-Tc integrated circuit

International Nuclear Information System (INIS)

Anon.

1991-01-01

This paper reports that researchers at Conductus have successfully demonstrated what the company says is the world's first integrated circuit containing active devices made from high-temperature superconductors. The circuit is a SQUID magnetometer made from seven layers of material: three layers of yttrium-barium-copper oxide, two layers of insulating material, a seed layer to create grain boundaries for the Josephson junctions, and a layer of silver for making electrical contact to the device. The chip also contains vias, or pathways that make a superconducting contact between the superconducting layers otherwise separated by insulators. Conductus had previously announced the development of a SQUID magnetometer that featured a SQUID sensor and a flux transformer manufactured on separate chips. What makes this achievement important is that the company was able to put both components on the same chip, thus creating a simple integrated circuit on a single chip. This is still a long way from conventional semiconductor technology, with as many as a million components per chip, or even the sophisticated low-Tc superconducting chips made by the Japanese, but the SQUID magnetometer demonstrates all the elements and techniques necessary to build more complex high-temperature superconductor integrated circuits, making this an important first step
Superconductivity in transparent zinc-doped In2O3 films having low carrier density

Directory of Open Access Journals (Sweden)

Kazumasa Makise, Nobuhito Kokubo, Satoshi Takada, Takashi Yamaguti, Syunsuke Ogura, Kazumasa Yamada, Bunjyu Shinozaki, Koki Yano, Kazuyoshi Inoue and Hiroaki Nakamura

2008-01-01

Full Text Available Thin polycrystalline zinc-doped indium oxide (In2O3–ZnO films were prepared by post-annealing amorphous films with various weight concentrations x of ZnO in the range 0≤x ≤0.06. We have studied the dependences of the resistivity ρ and Hall coefficient on temperature T and magnetic field H in the range 0.5≤T ≤300 K, H≤6 Tfor 350 nm films annealed in air. Films with 0≤x≤0.03 show the superconducting resistive transition. The transition temperature Tc is below 3.3 K and the carrier density n is about 1025–1026 m−3. The annealed In2O3–ZnO films were examined by transmission electron microscopy and x-ray diffraction analysis revealing that the crystallinity of the films depends on the annealing time. We studied the upper critical magnetic field Hc2 (T for the film with x = 0.01. From the slope of dHc2 /dT, we obtain the coherence length ξ (0 ≈ 10 nm at T = 0 K and a coefficient of electronic heat capacity that is small compared with those of other oxide materials.
Trapped magnetic field of a superconducting bulk magnet in high- Tc RE-Ba-Cu-O

International Nuclear Information System (INIS)

Fujimoto, Hiroyuki; Yoo, Sang Im; Higuchi, Takamitsu; Nakamura, Yuichi; Kamijo, Hiroki; Nagashima, Ken; Murakami, Masato

1999-01-01

Superconducting magnets made of high-T c superconductors are promising for industrial applications. It is well known that REBa 2 Cu 3 O 7-x and LRE (light rare-earth) Ba 2 Cu 3 O 7-x superconductors prepared by melt processes have a high critical current density, J c , at 77 K and high magnetic fields. Therefore, the materials are very prospective for high magnetic field application as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. LREBaCuO bulks, compared with REBaCuO bulks, exhibit a larger J c in high magnetic fields and a much improved irreversibility field, H irr , at 77 K. In this study, we discuss the possibility and trapped field properties of a superconducting bulk magnet, as well as the melt processing for bulk superconductors and their characteristic superconducting properties. One of the applications is a superconducting magnet for the future magnetically levitated (Maglev) train
Gold nanocrystals in high-temperature superconducting films: Creation of pinning patterns of choice

Energy Technology Data Exchange (ETDEWEB)

Katzer, Christian; Michalowski, Peter; Schmidl, Frank; Seidel, Paul [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, 07743 Jena (Germany); Stahl, Claudia; Treiber, Sebastian; Schuetz, Gisela [Max-Planck-Institut fuer Intelligente Systeme, Heisenbergstrasse 3, 70569 Stuttgart (Germany); Christiani, Georg [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Albrecht, Joachim [Hochschule Aalen, Beethovenstrasse 1, 73430 Aalen (Germany)

2013-07-01

Many superconducting thin film devices require a spatially resolved current carrying capability due to different boundary conditions. On the one hand, the critical current density and the pinning of flux lines respectively should be high to reduce flux noise in the antenna regions of gradiometers; on the other hand, the critical current density of the Josephson junctions itself must not be too high to ensure a proper functionality. We report that adding gold nanoparticles during the preparation process of epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-δ} thin films offers the possibility of creating spatially varying flux pinning properties, thus allowing to locally enhance the critical current density up to a factor of two. Magneto-optical investigations as well as transport measurements will be presented, indicating that an Au particle induced modification of the YBCO pinning properties allows the engineering of the critical current landscape on the sub-micrometre scale.

Interdiffusion studies on high-Tc superconducting YBa2Cu3O7-δ thin films on Si(111) with a NiSi2/ZrO2 buffer layer

DEFF Research Database (Denmark)

Aarnink, W.A.M.; Blank, D.H.A.; Adelerhof, D.J.

1991-01-01

Interdiffusion studies on high-T(c) superconducting YBa2Cu3O7-delta thin films with thickness in the range of 2000-3000 angstrom, on a Si(111) substrate with a buffer layer have been performed. The buffer layer consists of a 400 angstrom thick epitaxial NiSi2 layer covered with 1200 angstrom...... of polycrystalline ZrO2. YBa2Cu3O7-delta films were prepared using laser ablation. The YBa2Cu3O7-delta films on the Si/NiSi2/ZrO2 substrates are of good quality; their critical temperatures T(c,zero) and T(c,onset) have typical values of 85 and 89 K, respectively. The critical current density j(c) at 77 K equaled 4...... x 10(4) A/cm2. With X-ray analysis (XRD), only c-axis orientation has been observed. The interdiffusion studies, using Rutherford backscattering spectrometry (RBS) and scanning Auger microscopy (SAM) show that the ZrO2 buffer layer prevents severe Si diffusion to the YBa2Cu3O7-delta layer, the Si...
Carbon-based superconductors towards high-Tc superconductivity

CERN Document Server

Haruyama, Junji

2014-01-01

Introduction of Condensed Matter Physics; Spin-state Crossover; Li Ion Battery; Huge Thermoelectric Power; Room-temperature Ferromagnetism; Partially Disordered Antiferromagnetic Transition; Superconductivity; Transport Properties Combined with Charge, Spin, and Orbital; Magnetoresistance and Spin Blocade; Intrinsic Inhomogeneity; Move/diffuse and Charge/discharge Effect.
Quenching of superconductivity in disordered thin films by phase fluctuations

International Nuclear Information System (INIS)

Hebard, A.F.; Palaanen, M.A.

1992-01-01

The amplitude Ψ 0 and phase Φ of the superconducting order parameter in thin-film systems are affected differently by disorder and dimensionality. With increasing disorder superconducting long range order is quenched in sufficiently thin films by physical processes driven by phase fluctuations. This occurs at both the zero-field vortex-antivortex unbinding transition and at the zero-temperature magnetic-field-tuned superconducting-insulating transition. At both of these transitions Ψ 0 is finite and constant, vanishing only when temperature, disorder, and/or magnetic field are increased further. Experimental results on amorphous-composite InO x films are presented to illustrate these points and appropriate comparisons are made to other experimental systems. (orig.)
Ferromagnetic Film on a Superconducting Substrate

OpenAIRE

Bulaevskii, L. N.; Chudnovsky, E. M.

2000-01-01

We study the equilibrium domain structure and magnetic flux around a ferromagnetic (FM) film with perpendicular magnetization M_0 on a superconducting (SC) substrate. At 4{\\pi}M_0> 1. Here \\lambda_L is the London penetration length. For 4{\\pi}M_0 > H_{c1} and l_{N} in excess of about 35 {\\lambda}_{L}, the domains are connected by SC vortices. We argue that pinning of vortices by magnetic domains in FM/SC multilayers can provide high critical currents.
Superconductivity of Rock-Salt Structure LaO Epitaxial Thin Film.

Science.gov (United States)

Kaminaga, Kenichi; Oka, Daichi; Hasegawa, Tetsuya; Fukumura, Tomoteru

2018-06-06

We report a superconducting transition in a LaO epitaxial thin film with the superconducting transition onset temperature ( T c ) at around 5 K. This T c is higher than those of other lanthanum monochalcogenides and opposite to their chemical trend: T c = 0.84, 1.02, and 1.48 K for LaX (X = S, Se, Te), respectively. The carrier control resulted in a dome-shaped T c as a function of electron carrier density. In addition, the T c was significantly sensitive to epitaxial strain in spite of the highly symmetric crystal structure. This rock-salt superconducting LaO could be a building block to design novel superlattice superconductors.
Superconducting properties of Pb82Bi18 films controlled by ferromagnetic nanowire arrays

International Nuclear Information System (INIS)

Ye Zuxin; Lyuksyutov, Igor F; Wu Wenhao; Naugle, Donald G

2011-01-01

The superconducting properties of Pb 82 Bi 18 alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb 82 Bi 18 films are then quench condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb 82 Bi 18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and material variety was observed.
Superconducting properties of Pb82Bi18 films controlled by ferromagnetic nanowire arrays

Science.gov (United States)

Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.

2011-02-01

The superconducting properties of Pb82Bi18 alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb82Bi18 films are then quench condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb82Bi18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and material variety was observed.
Plasma-enhanced chemical vapor deposition for YBCO film fabrication of superconducting fault-current limiter

Energy Technology Data Exchange (ETDEWEB)

Jun, Byung Hyuk; Kim, Chan Joong

2006-05-15

Since the high-temperature superconductor of oxide type was founded, many researches and efforts have been performed for finding its application field. The YBCO superconducting film fabricated on economic metal substrate with uniform critical current density is considered as superconducting fault-current limiter (SFCL). There are physical and chemical processes to fabricate superconductor film, and it is understood that the chemical methods are more economic to deposit large area. Among them, chemical vapor deposition (CVD) is a promising deposition method in obtaining film uniformity. To solve the problems due to the high deposition temperature of thermal CVD, plasma-enhanced chemical vapor deposition (PECVD) is suggested. This report describes the principle and fabrication trend of SFCL, example of YBCO film deposition by PECVD method, and principle of plasma deposition.
Elliptical vortex and oblique vortex lattice in the FeSe superconductor based on the nematicity and mixed superconducting orders

Science.gov (United States)

Lu, Da-Chuan; Lv, Yang-Yang; Li, Jun; Zhu, Bei-Yi; Wang, Qiang-Hua; Wang, Hua-Bing; Wu, Pei-Heng

2018-03-01

The electronic nematic phase is characterized as an ordered state of matter with rotational symmetry breaking, and has been well studied in the quantum Hall system and the high-Tc superconductors, regardless of cuprate or pnictide family. The nematic state in high-Tc systems often relates to the structural transition or electronic instability in the normal phase. Nevertheless, the electronic states below the superconducting transition temperature is still an open question. With high-resolution scanning tunneling microscope measurements, direct observation of vortex core in FeSe thin films revealed the nematic superconducting state by Song et al. Here, motivated by the experiment, we construct the extended Ginzburg-Landau free energy to describe the elliptical vortex, where a mixed s-wave and d-wave superconducting order is coupled to the nematic order. The nematic order induces the mixture of two superconducting orders and enhances the anisotropic interaction between the two superconducting orders, resulting in a symmetry breaking from C4 to C2. Consequently, the vortex cores are stretched into an elliptical shape. In the equilibrium state, the elliptical vortices assemble a lozenge-like vortex lattice, being well consistent with experimental results.
Theoretical study of stability and superconductivity of ScHn (n =4 -8 ) at high pressure

Science.gov (United States)

Qian, Shifeng; Sheng, Xiaowei; Yan, Xiaozhen; Chen, Yangmei; Song, Bo

2017-09-01

The synthesis of hydrogen sulfides, with the potential of high-temperature superconductivity, was recently proposed at high Tc = 203 K. It motivated us to employ an ab initio approach for the predictions of crystal structures to find the stable scandium hydrides. In addition to the earlier predicted three stoichiometries of ScH, ScH2, and ScH3, we identify three other metallic stoichiometries of ScH4, ScH6, and ScH8, which show superconductivity at significantly higher temperatures. The phases of ScH4 and ScH6, whose stability does not require extremely high pressures (ZPE), are primarily ionic compounds containing exotic quasimolecular H2 arrangements. The present electron-phonon calculations revealed the superconductive potential of ScH4 and ScH6 with estimated Tc of 98 K and 129 K at 200 GPa and 130 GPa, respectively. The superconductivity of ScHn stems from the large electron-phonon coupling associated with the wagging, bending, and intermediate-frequency modes attributed mainly to the hydrogen atoms.
Unconventional superconductivity in heavy fermionic and high-Tc superconductors

International Nuclear Information System (INIS)

Volovik, G.E.

1989-01-01

Splitting of the superconducting transition and glass spectrum in heavy fermion companies and oxide superconductors are discussed. The multicomponent order parameter leads to splitting of transition due to magnetic field, impurities, orthorhombic distortion, etc... Linear specific heat in oxide superconductors may be explained in terms of the Fermi-surface arising in superconducting state if interband is pairing strong enough
Y-Ba-Cu-O superconducting thin films by simultaneous or sequential evaporation

International Nuclear Information System (INIS)

Mogro-Campero, A.; Hunt, B.D.; Turner, L.G.; Burrell, M.C.; Balz, W.E.

1988-01-01

Superconducting thin films of Y-Ba-Cu-O near the 1:2:3 stoichiometry were produced by simultaneous (coevaporation) and sequential (multilayer) evaporation in the same evaporator. The best film obtained on yttria-stabilized zirconia (YSZ) had a superconducting onset temperature of 104 K, a midpoint T/sub c/ of 92 K, and zero resistance at T≤74 K. Stoichiometry was deduced by inductively coupled plasma emission spectroscopy, and elemental depth profiles were obtained by x-ray photoelectron spectroscopy. Film stoichiometry changes only near the film/substrate boundary for films on YSZ. Films on Si/SiO 2 were not superconducting; depth profiling shows severe changes of film composition with depth. A major theme of this work is process reproducibility, which was found to be poor for coevaporation but improved considerably for sequential evaporation
Ultrathin NbN film superconducting single-photon detector array

International Nuclear Information System (INIS)

Smirnov, K; Korneev, A; Minaeva, O; Divochiy, A; Tarkhov, M; Ryabchun, S; Seleznev, V; Kaurova, N; Voronov, B; Gol'tsman, G; Polonsky, S

2007-01-01

We report on the fabrication process of the 2 x 2 superconducting single-photon detector (SSPD) array. The SSPD array is made from ultrathin NbN film and is operated at liquid helium temperatures. Each detector is a nanowire-based structure patterned by electron beam lithography process. The advances in fabrication technology allowed us to produce highly uniform strips and preserve superconducting properties of the unpatterned film. SSPD exhibit up to 30% quantum efficiency in near infrared and up to 1% at 5-μm wavelength. Due to 120 MHz counting rate and 18 ps jitter, the time-domain multiplexing read-out is proposed for large scale SSPD arrays. Single-pixel SSPD has already found a practical application in non-invasive testing of semiconductor very-large scale integrated circuits. The SSPD significantly outperformed traditional single-photon counting avalanche diodes
Spatial characterization of the edge barrier in wide superconducting films

Science.gov (United States)

Sivakov, A. G.; Turutanov, O. G.; Kolinko, A. E.; Pokhila, A. S.

2018-03-01

The current-induced destruction of superconductivity is discussed in wide superconducting thin films, whose width is greater than the magnetic field penetration depth, in weak magnetic fields. Particular attention is paid to the role of the boundary potential barrier (the Bin-Livingston barrier) in critical state formation and detection of the edge responsible for this critical state with different mutual orientations of external perpendicular magnetic field and transport current. Critical and resistive states of the film were visualized using the space-resolving low-temperature laser scanning microscopy (LTLSM) method, which enables detection of critical current-determining areas on the film edges. Based on these observations, a simple technique was developed for investigation of the critical state separately at each film edge, and for the estimation of residual magnetic fields in cryostats. The proposed method only requires recording of the current-voltage characteristics of the film in a weak magnetic field, thus circumventing the need for complex LTLSM techniques. Information thus obtained is particularly important for interpretation of studies of superconducting film single-photon light emission detectors.
Approaches to the high Tc superconductivity in β-(BEDT-TTF)2X structure

International Nuclear Information System (INIS)

Tokumoto, M.; Anzai, H.; Murata, K.; Bando, H.; Kajimura, K.; Morita, S.; Ishiguro, T.; Saito, G.

1987-01-01

Experimental strategies to realize a high T c superconductivity comparable with the high-T c state of β-(BEDT-TTF) 2 I 3 by means of modification of the β-(BEDT-TTF) 2 X structure are discussed. Some experimental results related to such trials are presented, including the effect of anion alloying and the effect of solvent used for crystal growth on the superconductivity in β-(BEDT-TTF) 2 I 3 . (orig.)
International Discussion Meeting on High-Tc Superconductors

CERN Document Server

1988-01-01

In the past two years conferences on superconductivity have been characterized by the attendance of hundreds of scientists. Consequently, the organizers were forced to schedule numerous parallel sessions and poster presentations with an almost unsurveyable amount of information. It was, therefore, felt that a more informal get-together, providing ample time for a thourough discussion of some topics of current interest in high-temperature superconductivity, was timely and benefitial for leading scientists as well as for newcomers in the field. The present volume contains the majority of papers presented at the International Discussion Meeting on High-Tc Superconductors held at the Mauterndorf Castle in the Austrian Alps from February 7 to 11, 1988. Each subject was introduced in review form by a few invited speakers and then discussed together with the contributed poster presentations. These discussion sessions chaired by selected scientists turned out to be the highlights of the meeting, not only because all ...
Superconductivity of a Sn film controlled by an array of Co nanowires

Science.gov (United States)

Wei, Z.; Ye, Z.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Wu, W.; Naugle, D. G.

2012-09-01

Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized Anodic Aluminum Oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.
Superconductivity of a Sn film controlled by an array of Co nanowires

International Nuclear Information System (INIS)

Wei, Z.; Ye, Z.; Rathnayaka, K.D.D.; Lyuksyutov, I.F.; Wu, W.; Naugle, D.G.

2012-01-01

Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized Anodic Aluminum Oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.
Josephson plasma resonance in superconducting multilayers

DEFF Research Database (Denmark)

Pedersen, Niels Falsig

1999-01-01

We derive an analytical solution for the josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low T-c systems with magnetic coupling between the superconducting layers, but many features of our results are more general, and thus an application...... to the recently derived plasma resonance phenomena for high T-c superconductors of the BSCCO type is discussed....
Magnetically-related properties of bismuth containing high Tc superconductors

Science.gov (United States)

Vezzoli, Gary C.; Chen, M. F.; Craver, F.; Safari, A.; Moon, B. M.; Lalevic, B.; Burke, Terence; Shoga, M.

1990-08-01

The effect of magnetic fields to 15 T on electrical resistance has been measured for the BiSrCaCuO superconductor at precise temperatures during the transition to the superconducting state from pre-onset conditions to essentially zero resistance conditions. The results show that the temperature at which the magnetic field causes a divergence in the resistance versus 1000/ T curve is approximately the same temperature as the value at which, during cooling, the positive Hall coefficient begins its abrupt descent to zero. This temperature gives the best measure of Tc. It is also shown that small oscillations of low frequency start near onset conditions, the amplitude of which at a given temperature is B-field dependent. Additionally, Hall effect studies as a function of temperature at 4 T in three separate experiments (including high Tc BiSrCaCu PbO of > 90% theoretical density) show that sharp delta-function-like peaks in + RH are observed near Tc and are superimposed on a broader maximum. The Hall data are explicable in terms of exciton formation and ionization. The bound holes associated with these excitons are believed to be the mediators producing Cooper-pairing, and scale very well with Tc for all the known high Tc oxides.

One- and two-dimensional sublattices as preconditions for high-Tc superconductivity

International Nuclear Information System (INIS)

Krueger, E.

1989-01-01

In an earlier paper it was proposed describing superconductivity in the framework of a nonadiabatic Heisenberg model in order to interprete the outstanding symmetry proper ties of the (spin-dependent) Wannier functions in the conduction bands of superconductors. This new group-theoretical model suggests that Cooper pair formation can only be mediated by boson excitations carrying crystal-spin-angular momentum. While in the three-dimensionally isotropic lattices of the standard superconductors phonons are able to transport crystal-spin-angular momentum, this is not true for phonons propagating through the one- or two-dimensional Cu-O sublattices of the high-T c compounds. Therefore, if such an anisotropic material is superconducting, it is necessarily higher-energetic excitations (of well-defined symmetry) which mediate pair formation. This fact is proposed being responsible for the high transition temperatures of these compounds. (author)
Extended abstracts of the 12th JAERI workshop on high-Tc superconductors

Energy Technology Data Exchange (ETDEWEB)

Hojou, Kiichi; Okayasu, Satoru; Sasase, Masato [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Ishida, Takekazu [Osaka Prefectual Univ., Sakai (JP)] (eds.)

2001-03-01

This workshop was held on December 7-8, 2000 at JAERI (Tokai). The research group at JAERI shares a responsibility for material modification of high-Tc superconductors by irradiation in 'the multi-core project II of the high temperature superconducting material research' organized by STA (Science and Technology Agency) of Japan. This report contains the extended abstracts of workshop presentations covering basic theories, various experimental results and material improvement studies of the superconductivity by high energy ion irradiation. The twelve presentations of the workshop were devoted to a mini symposium where the direct observations of vortices were discussed in view of the various sophisticated techniques. (author)
Extended abstracts of the 12th JAERI workshop on high-Tc superconductors

International Nuclear Information System (INIS)

Hojou, Kiichi; Okayasu, Satoru; Sasase, Masato

2001-03-01

This workshop was held on December 7-8, 2000 at JAERI (Tokai). The research group at JAERI shares a responsibility for material modification of high-Tc superconductors by irradiation in 'the multi-core project II of the high temperature superconducting material research' organized by STA (Science and Technology Agency) of Japan. This report contains the extended abstracts of workshop presentations covering basic theories, various experimental results and material improvement studies of the superconductivity by high energy ion irradiation. The twelve presentations of the workshop were devoted to a mini symposium where the direct observations of vortices were discussed in view of the various sophisticated techniques. (author)
RF Characterization of Niobium Films for Superconducting Cavities

CERN Document Server

Aull† , S; Doebert, S; Junginger, T; Ehiasarian, AP; Knobloch, J; Terenziani, G

2013-01-01

The surface resistance RS of superconductors shows a complex dependence on the external parameters such as temperature, frequency or radio-frequency (RF) field. The Quadrupole Resonator modes of 400, 800 and 1200 MHz allow measurements at actual operating frequencies of superconducting cavities. Niobium films on copper substrates have several advantages over bulk niobium cavities. HIPIMS (High-power impulse magnetron sputtering) is a promising technique to increase the quality and therefore the performance of niobium films. This contribution will introduce CERNs recently developed HIPIMS coating apparatus. Moreover, first results of niobium coated copper samples will be presented, revealing the dominant loss mechanisms.
Laser-excited photoemission spectroscopy study of superconducting boron-doped diamond

Directory of Open Access Journals (Sweden)

K. Ishizaka, R. Eguchi, S. Tsuda, T. Kiss, T. Shimojima, T. Yokoya, S. Shin, T. Togashi, S. Watanabe, C.-T. Chen, C.Q. Zhang, Y. Takano, M. Nagao, I. Sakaguchi, T. Takenouchi and H. Kawarada

2006-01-01

Full Text Available We have investigated the low-energy electronic state of boron-doped diamond thin film by the laser-excited photoemission spectroscopy. A clear Fermi-edge is observed for samples doped above the semiconductor–metal boundary, together with the characteristic structures at 150×n meV possibly due to the strong electron–lattice coupling effect. In addition, for the superconducting sample, we observed a shift of the leading edge below Tc indicative of a superconducting gap opening. We discuss the electron–lattice coupling and the superconductivity in doped diamond.
Ultrathin NbN Films for Superconducting Single-Photon Detectors

International Nuclear Information System (INIS)

Slysz, W.; Guziewicz, M.; Borysiewicz, M.

2011-01-01

We present our research on fabrication and structural and transport characterization of ultrathin superconducting NbN layers deposited on both single-crystal Al 2 O 3 and Si wafers, and SiO 2 and Si 3 N 4 buffer layers grown directly on Si wafers. The thicknesses of our films varied from 6 nm to 50 nm and they were grown using reactive RF magnetron sputtering on substrates maintained at the temperature 850 o C. We have performed extensive morphology characterization of our films using the X-ray diffraction method and atomic force microscopy, and related the results to the type of the substrate used for the film deposition. Our transport measurements showed that even the thinnest, 6 nm thick NbN films had the superconducting critical temperature of 10-12 K, which was increased to 14 K for thicker films. (author)
A Method for Suppressing Superconductivity of Thin Films

Science.gov (United States)

Suppula, Tarmo; Pekola, Jukka; Kauppinen, Juha

2003-03-01

We have developed a method for suppressing superconductivity of thin films. Thin stripes of cobalt grown by e-gun evaporation and patterned by e-beam lithography were placed in the vicinity of aluminium thin film structures. The cobalt stripes were magnetized at 4.2 K with a superconducting coil and the remanence suppressed superconductivity of the Al stripe at temperatures down to 50 mK at least. The magnetization remained in thermal cycling and in a longer storage at room temperature. Motivation for this work is the Coulomb Blockade Thermometer(CBT)^1 which has to be in a normal state to operate. The CBT sensor contains aluminium which is superconducting at temperatures below 1.4 K. An external magnetic field is not always available or acceptable in cryostats. A small grain of permanent magnet mounted to the sensor is another solution, but suspicious if the sensor is put in strong magnetic fields or if "zero field" environment is required. We have shown that suitably patterned and magnetized Co stripes in the vicinity of tunnel junctions of the CBT can solve this problem. The amount of magnetic material in the sensor, as well as the stray field, is very small. This technique may be useful in other low temperature thin film devices also. 1) Product of Nanoway Ltd.
Fabrication of thick superconducting films by decantation

Directory of Open Access Journals (Sweden)

Julián Betancourt M.

1991-07-01

Full Text Available We have found superconducting behavior in thick films fabricated by decantation. In this paper we present the experimental method and results obtained using commercial copper substrates.
Novel structures and superconductivities of calcium–lithium alloys at high pressures: A first-principles study

International Nuclear Information System (INIS)

Xu, Ying; Chen, Changbo; Wang, Sihan; Sun, Xiuping

2016-01-01

Exposing a material to high pressures can fundamentally influence its crystal and electronic structure, leading to the formation of new materials with unique physical and chemical properties. Here, we have conducted a systematic search for Ca–Li alloys by using a global minima search based on particle-swarm optimization algorithm in combination with density functional theory calculations. We predict that Calcium and Lithium with a high Ca composition CaLi, Ca_2Li and Ca_3Li exist, and a strikingly decomposition-combination-decomposition oscillating behavior with pressure is revealed. All predicted Ca–Li compounds are metallic and good electron–phonon superconductors with transition temperatures (T_c) of around 8–19 K. The superconductivity mainly originates from the low-energy Ca vibrations and the pressure dependence of T_c is dominated by the phonon softening/hardening. - Highlights: • Three high Ca compositions of CaLi, Ca_2Li, and Ca_3Li alloys have been predicted. • High superconducting temperatures were predicted for Ca–Li alloys at high pressures. • The origin of the superconductivity is revealed. • The superconducting temperature increases with increasing pressures for Fd-3m CaLi. • The Fd-3m phase of CaLi is a potential high-temperature superconductor.
High-Tc superconductivity of Tl-Ba-Ca-Cu-O samples

International Nuclear Information System (INIS)

Porjesz, T.; Kirschner, I.; Kovacs, G.

1988-08-01

A TlBaCaCuO 4.5+x compound has been investigated from the point of view of superconductivity. Depending on the heat treatment, one part of the sample exhibits superconductivity with an onset of 121 K and zero resistivity of 106 K and the other part of them shows a sharp drop in resistivity at 130 K which hints at an existence of superconducting grains. This picture was confirmed by magnetic and ESR measurements giving possibility for estimation of critical magnetic fields. (author). 5 refs, 6 figs
Systematics in positron annihilation lifetime analysis of high Tc superconducting transitions

International Nuclear Information System (INIS)

Howell, R.H.; Radousky, H.B.; Wachs, A.L.; Fluss, M.J.; Turchi, P.E.A.; Jean, Y.C.; Sunder, C.S.; Chu, C.W.; Peng, J.L.; Folkerts, T.J.; Shelton, R.N.; Hinks, D.G.

1989-01-01

Values of the positron lifetime have previously been observed to change with temperature below T c in high T c superconducting oxides. The authors report new measurements on Ba .6 K .4 Bio 3 and Nd 1.85 Ce .15 CuO 4
Analysis of influence of buffer layers on microwave propagation through high-temperature superconducting thin films

International Nuclear Information System (INIS)

Ceremuga, J.; Barton, M.; Miranda, F.

1994-01-01

Methods of analysis of microwave propagation through superconducting thin films with buffer layers on dielectric substrates have been discussed. Expressions describing the transmission coefficient S 21 through the structure and the complex conductivity sigma of a superconductor in an analytical form have been derived. The derived equations are valid for microwave propagation in waveguides as well as in free space with relevant definition of impedances. Using the obtained solutions, the influences of buffer layers' parameters (thickness, relative permittivity and loss tangent) on the transmission coefficient has been investigated using MATLAB. Simulations have been performed for 10 GHz transmission through YBa 2 Cu 3 O 7 films on sapphire with SrTiO 3 and CeO 2 buffer layers and on silicon with CaF 2 and YSZ buffer layers. To illustrate the simulations, measurements of the transmission through YBCO film on sapphire with SrTiO 3 buffer layer have been performed. It has been shown that even lossy buffer layers have very little impact (smaller than 1% in magnitude and 0.3% in phase) on the transmission coefficient through superconducting thin films, providing their thickness is below 10 mu m. (author)
Harmonic generation effect in high-Tc films

International Nuclear Information System (INIS)

Khare, Neeraj; Shrivastava, S.K.; Padmanabhan, V.P.N.; Khare, Sangeeta; Gupta, A.K.

1997-01-01

Harmonic generation in thick BPSCCO and thin YBCO films are reported. The application of an ac field (H ac > H c1 ) of frequency f causes the generation of odd harmonics of frequency (2n+1)f. The application of dc field in addition to the ac field causes the appearance of even harmonics also in the BPSCCO film. However, the appearance of even harmonics is not observed in YBCO film with high J c ∼ 1.6x10 6 A/cm 2 and appearance of second harmonic with small magnitude is observed in YBCO film with low J c ∼ 2x10 3 A/cm 2 . The variation of amplitudes of these harmonics are studied as a function of magnitude of ac and dc field and the results are explained in the framework of critical state model. A high-T c film magnetometer based on the measurement of the amplitude of second harmonic has been developed whose field sensitivity is ∼ 1.5x10 -8 T. (author)
Processing of flexible high-Tc superconducting wires

International Nuclear Information System (INIS)

Lee, B.I.; Modi, V.

1989-01-01

Wires superconducting at temperatures above 77 K are produced by using YBa 2 Cu 3 O 7 materials. Flexibility was obtained by support from prefabricated fibers or a metallic coating on the extruded YBa 2 Cu 3 O 7 wires. The microstructure, the T c and the critical current densities of the wires were determined. Processing variables and steps are described
Vortex loops in the critical Casimir effect in superfluid and superconducting films

International Nuclear Information System (INIS)

Williams, Gary A.

2004-01-01

Vortex-loop renormalization techniques are used to calculate the magnitude of the critical Casimir forces in superfluid and superconducting thin films. The force is found to become appreciable when the size of the thermally excited vortex loops is comparable to the film thickness, and the results for T c are found to match very well with perturbative renormalization-group theories that can only be carried out for T>T c . In helium films the Casimir force leads to a change in the film thickness close to T c that has been observed experimentally. A similar effect is predicted to occur near the transition temperature of high-T c superconducting films, which is also a vortex-loop phase transition. In this case the Casimir force takes the form of a voltage difference that will appear at the junction between a thin film and a bulk sample. Estimates show that this voltage can be appreciable (tens of microvolts), and it may be possible to observe the effect by measuring the voltage across two Josephson tunnel junctions to the film and to the bulk, using a SQUID voltmeter
Crystal layered structure and superconducting high-Tc behaviour of the mercurocuprates

International Nuclear Information System (INIS)

Kuzemsky, A.L.; Kuzemskaya, I.G.; Cheglokov, A.A.

1998-10-01

The high-T c superconducting behaviour of the mercurocuprate family HgBa 2 Ca n-1 Cu n O 2n+2+δ was analyzed from the point of view of their layered crystal structure. A dependence of superconducting critical temperature for different members of mercurocuprate family was studied in terms of phenomenological model of layered superconductors. The redistribution of charge was taken into account. This leads to an observable nonmonotonic ''bell''-shaped dependence of T c (n) with a maximum at n=3 and provides a quantitative explanation of the experiments. It was shown that the correlations between the copper valence, lattice parameters, extra oxygen contents and number of layers are essential factors for the physical behaviour and HTSC characterization of the mercurocuprates. (author)
The Use of OXYGEN-18 in the Development of Methods for Controlled Sputter Deposition of High Critical Transition Temperature Material Thin Films of Predicted Composition and Good Uniformity

Science.gov (United States)

Tidrow, Steven Clay

Two primary concerns, in the sputter deposition of high T_{c} material films, are the prevention of oxygen deficiency in the films and the elimination of the negative ion effect. "Oxygen deficiency" occurs when the amount of oxygen incorporated into the film is less than the amount of oxygen required to form the superconducting material lattice. Oxygen deficiency is due to the volatile nature of oxygen. The negative ion effect occurs when an atom or molecule (typically oxygen) gains an extra electron, is accelerated away from the target and impinges upon a film being grown directly in front of the sputtering target. The impinging particle has enough energy to cause resputtering of the deposited film. The presence of Sr and to a greater extent Ba, may enhance the negative ion effect in these materials. However, it is oxygen which readily forms negative ions that is primarily responsible for the negative ion effect. Thus, oxygen must be given special attention in the sputter deposition of high T_{c} material films. A specially designed sputtering system is used to demonstrate that the negative ion effect can be reduced such that large uniform high T_{c} material films possessing predicted and repeated composition can be grown in an on-axis arrangement. Utilizing this same sputtering system and the volatile nature of oxygen, it is demonstrated that oxygen processes occurring in the chamber during growth of high T_ {c} material films can be investigated using the tracer ^{18}O. In particular, it is shown that ^{18}O can be utilized as a tool for (1) investigating the negative ion effect, (2) investigating oxygen incorporation into high T_{c} material films, (3) investigating oxygen incorporation into the target, (4) tailoring films for oxygen migration and interface investigations and (5) tailoring films for the other specific oxygen investigations. Such sputtering systems that utilize the tracer ^{18}O are necessary for systematic growth of high T_ {c} material films
Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure

Science.gov (United States)

Ogusu, Hiroki; Takeshita, Nao; Izawa, Koichi; Yamaura, Jun-ichi; Ohishi, Yasuo; Tsutsui, Satoshi; Okamoto, Yoshihiko; Hiroi, Zenji

2010-11-01

Rattling-induced superconductivity in the β-pyrochlore oxide KOs2O6 is investigated under high pressure up to 5 GPa. Resistivity measurements in a high-quality single crystal reveal a gradual decrease in the superconducting transition temperature Tc from 9.7 K at 1.0 GPa to 6.5 K at 3.5 GPa, followed by a sudden drop to 3.3 K at 3.6 GPa. Powder X-ray diffraction experiments show a structural transition from cubic to monoclinic or triclinic at a similar pressure. The sudden drop in Tc is ascribed to this structural transition, by which an enhancement in Tc due to a strong electron-rattler interaction present in the low-pressure cubic phase is abrogated as the rattling of the K ion is completely suppressed or weakened in the high-pressure phase of reduced symmetry. In addition, we find two anomalies in the temperature dependence of resistivity in the low-pressure phase, which may be due to subtle changes in rattling vibration.
Effect of point disorder on superconducting properties of ultrathin epitaxial NbN films

International Nuclear Information System (INIS)

Jesudasan, John; Bagwe, Vivas; Mondal, Mintu; Chand, Madhavi; Kamlapure, Anand; Pai, S.P.; Raychaudhuri, Pratap; Mishra, Archana

2009-01-01

We synthesized homogeneously disordered epitaxial NbN films on MgO(100) substrates using reactive dc magnetron sputtering. The disorder of the films is characterized by the Loffe-Regel parameter k F I. The superconducting properties are studied through transport, ac-susceptibility measurements and electron tunneling. The superconducting transition temperature is studied as a function of thickness for films of different disorder. In the case of the less disordered film, there is a smooth decrease in T c with decreasing thickness but for the more disordered film, the T c shows a sharp decrease to zero at a threshold thickness. The superconducting energy gap is studied via planar tunnel junctions. It is found that for the less disordered films, the temperature dependence of the gap follows the BCS variation but for the more disordered ones, there is a significant deviation from the BCS curve, and the gap remains finite at T c indicating that the superconducting transition is either governed by phase fluctuations or a first order phase transition. (author)
MgB2 superconducting wires basics and applications

CERN Document Server

2016-01-01

The compendium gives a complete overview of the properties of MgB2 (Magnesium Diboride), a superconducting compound with a transition temperature of Tc = 39K, from the fundamental properties to the fabrication of multifilamentary wires and to the presentation of various applications. Written by eminent researchers in the field, this indispensable volume not only discusses superconducting properties of MgB2 compounds, but also describes known preparation methods of thin films and of bulk samples obtained under high pressure methods. A unique selling point of the book is the detailed coverage of various applications based on MgB2, starting with MRI magnets and high current cables, cooled by Helium (He) vapor. High current cables cooled by liquid hydrogen are also highlighted as an interesting alternative due to the shrinking He reserves on earth. Other pertinent subjects comprise permanent magnets, ultrafine wires for space applications and wind generator projects.

Non-equilibrium spectroscopy of high-Tc superconductors

International Nuclear Information System (INIS)

Krasnov, V M

2009-01-01

In superconductors, recombination of two non-equilibrium quasiparticles into a Cooper pair results in emission of excitation that mediates superconductivity. This is the basis of the proposed new type of 'non-equilibrium' spectroscopy of high T c superconductors, which may open a possibility for direct and unambiguous determination of the coupling mechanism of high T c superconductivity. In case of low T c superconductors, the feasibility of such the non-equilibrium spectroscopy was demonstrated in classical phonon generation-detection experiments almost four decades ago. Recently it was demonstrated that a similar technique can be used for high T c superconductors, using natural intrinsic Josephson junctions both for injection of non-equilibrium quasiparticles and for detection of the non-equilibrium radiation. Here I analyze theoretically non-equilibrium phenomena in intrinsic Josephson junctions. It is shown that extreme non-equilibrium state can be achieved at bias equal to integer number of the gap voltage, which can lead to laser-like emission from the stack. I argue that identification of the boson type, constituting this non-equilibrium radiation would unambiguously reveal the coupling mechanism of high Tc superconductors.
THz spectroscopy on superconducting NbN thin films

Energy Technology Data Exchange (ETDEWEB)

Daschke, Lena; Pracht, Uwe S.; Dressel, Martin; Scheffler, Marc [1. Physikalisches Institut, Universitaet Stuttgart (Germany); Ilin, Konstantin S.; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Karlsruher Institut fuer Technologie (Germany)

2015-07-01

Epitaxial thin-film niobium nitride (NbN) is a conventional BCS superconductor. In presence of strong disorder, however, electronic inhomogeneities appear, which is not fully understood yet. To obtain a better insight into the physics of such disordered materials, studies on model systems such as structurally tailored films might be useful. Furthermore, disordered NbN films are used for single-photon detection devices, whose proper performance depends on a profound understanding of the superconducting properties. The studied NbN films have a T{sub c} ranging from 10 to 15 K and the superconducting energy gap is easily accessible with THz spectroscopy (0.4 - 5.6 meV). We investigate thin films of NbN sputtered on a sapphire substrate. With a Mach-Zehnder interferometer we measure the amplitude and phase shift of radiation transmitted through the thin-film sample. From there we can determine the real and imaginary parts of the optical conductivity. These results give information about the energy gap, Cooper pair density, and quasiparticle dynamics, including the temperature evolution of these quantities. We found that a film with 10 nm thickness roughly follows the BCS behavior, as expected. We will present results of our measurements on several different NbN samples.
Superconductivity and fast proton transport in nanoconfined water

Science.gov (United States)

Johnson, K. H.

2018-04-01

A real-space molecular-orbital density-wave description of Cooper pairing in conjunction with the dynamic Jahn-Teller mechanism for high-Tc superconductivity predicts that electron-doped water confined to the nanoscale environment of a carbon nanotube or biological macromolecule should superconduct below and exhibit fast proton transport above the transition temperature, Tc ≅ 230 K (-43 °C).
Tunneling probe of fluctuating superconductivity in disordered thin films

Science.gov (United States)

Dentelski, David; Frydman, Aviad; Shimshoni, Efrat; Dalla Torre, Emanuele G.

2018-03-01

Disordered thin films close to the superconductor-insulator phase transition (SIT) hold the key to understanding quantum phase transition in strongly correlated materials. The SIT is governed by superconducting quantum fluctuations, which can be revealed, for example, by tunneling measurements. These experiments detect a spectral gap, accompanied by suppressed coherence peaks, on both sides of the transition. Here we describe the insulating side in terms of a fluctuating superconducting field with finite-range correlations. We perform a controlled diagrammatic resummation and derive analytic expressions for the tunneling differential conductance. We find that short-range superconducting fluctuations suppress the coherence peaks even in the presence of long-range correlations. Our approach offers a quantitative description of existing measurements on disordered thin films and accounts for tunneling spectra with suppressed coherence peaks.
Far infrared spectroscopy of high-Tc superconductors at the National Synchrotron Light Source

International Nuclear Information System (INIS)

Perkowitz, S.; Williams, G.P.

1989-01-01

This paper reports the first far infrared transmission spectra for micron-thick films of high-T c rare-earth superconductors such as DyBaCuO, with implications for the superconducting gap. Spectra were obtained at Brookhaven's National Synchrotron Light Source, a new high-intensity, broad-band millimeter to infrared source. The National Synchrotron Light Source at Brookhaven National Laboratory, known for powerful X-ray and UV output, is also a high-intensity (10 to 1000 times above a black body), high-brightness (intensity per solid angle), broad-band, picosecond, millimeter to infrared source. These features make it valuable for far-infrared condensed matter experiments, especially those in highly absorbing or extremely small systems. A first application has been to measure very small infrared transmissions through thick bulk-like high-T c superconducting films. Preliminary measurements through films of the conventional superconductor Nb 3 Ge established techniques. These were followed by the first measurements (to the author's knowledge) through micron-thick films of high-T c rare-earth superconductors such as DyBaCuO over 10-300 cm -1 , which includes the superconducting gap according to BCS or moderately strong-coupled theory. The authors discuss the transmission evidence bearing on the existence of a gap and other important features of high-T c superconductors, and describe the synchrotron and instrumentation features which make possible these unusual measurements
First-Principles Study of Superconductivity in Ultra- thin Pb Films

Science.gov (United States)

Noffsinger, Jesse; Cohen, Marvin L.

2010-03-01

Recently, superconductivity in ultrathin layered Pb has been confirmed in samples with as few as two atomic layers [S. Qin, J. Kim, Q. Niu, and C.-K. Shih, Science 2009]. Interestingly, the prototypical strong-coupling superconductor exhibits different Tc's for differing surface reconstructions in samples with only two monolayers. Additionally, Tc is seen to oscillate as the number of atomic layers is increased. Using first principles techniques based on Wannier functions, we analyze the electronic structure, lattice dynamics and electron-phonon coupling for varying thicknesses and surface reconstructions of layered Pb. We discuss results as they relate to superconductivity in the bulk, for which accurate calculations of superconducting properties can be compared to experiment [W. L. McMillan and J.M. Rowell, PRL 1965]. This work was supported by National Science Foundation Grant No. DMR07-05941, the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Computational resources have been provided by the Lawrencium computational cluster resource provided by the IT Division at the Lawrence Berkeley National Laboratory (Supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231)
Vortex imaging in superconducting films by scanning Hall probe microscopy

International Nuclear Information System (INIS)

Oral, A.; Bending, S.J.; Humphreys, R.G.

1996-01-01

The authors have used a low noise Scanning Hall Probe Microscope (SHPM) to study vortex structures in superconducting films. The microscope has high magnetic field (∼2.9 x 10 -8 T/√Hz at 77K) and spatial resolution, ∼0.85 μm. Magnetic field profiles of single vortices in High T c YBa 2 Cu 3 O 7-δ thin films have been successfully measured and the microscopic penetration depth of the superconductor has been extracted as a function of temperature. Flux penetration into the superconductor has been imaged in real time (∼8s/frame)
Superatom representation of high-TC superconductivity

International Nuclear Information System (INIS)

Panas, Itai

2012-01-01

A “super-atom” conceptual interface between chemistry and physics is proposed in order to assist in the search for higher T C superconductors. The plaquettes generating the checkerboard superstructure in the cuprates, the C 60 molecules in K 3 C 60 , and the Mo 6 S 8 2- clusters in Chevrel phase materials offer such candidate super-atoms. Thus, in the present study high-T C superconductivity HTSC is articulated as the entanglement of two disjoint electronic manifolds in the vicinity of a common Fermi energy. The resulting HTSC ground state couples near-degenerate protected local super-atom states to virtual magnons in an antiferromagnetic AFM embedding. The composite Cooper pairs emerge as the interaction particles for virtual magnons mediated “self-coherent entanglement” of super-atom states. A Hückel type resonating valence bond RVB formalism is employed in order to illustrate the real-space Cooper pairs as well as their delocalization and Bose Einstein condensation BEC on a ring of super-atoms. The chemical potential μ BEC for Cooper pairs joining the condensate is formulated in terms of the super-exchange interaction, and consequently the T C in terms of the Neél temperature. A rationale for the robustness of the HTSC ground state is proposed: achieving local maximum “electron correlation entropy” at the expense of non-local phase rigidity.
6. Trilateral German-Russian-Ukrainian seminar on high-temperature superconductivity

International Nuclear Information System (INIS)

Aksenov, V.L.; Kornilov, E.I.

1993-01-01

The proceedings of the 6. Trilateral German-Russian-Ukrainian seminar on high-temperature superconductivity are reported. Nuclear methods (neutron diffraction, neutron polarization, Raman scattering, ESR) applied to study rare earth cuprates are described. The reports dealing with fundamental experimental studies and theoretical investigations are presented. The source materials for preparation of high-tc superconductors and the ways of their preparation, as well as their physico-chemical properties are considered
On characteristic voltage of the high Tc superconductor. [Y-Ba-Cu-O

Energy Technology Data Exchange (ETDEWEB)

Vasiliev, B V; Uchaikin, S V [Joint Inst. for Nuclear Research, Low Temperature Physics Dept., Dubna (USSR)

1991-12-01

The critical currents and normal resistances of the small bridges from yttrium-based high-Tc superconducting ceramics have been measured. The characteristic voltage of these bridges was found to be approximately 20{mu}V. This effect can be explained if between the ceramic grains there are contacts of an order of one crystalline cell in size. (orig.).
Complete Fabrication of a Traversable 3 µm Thick NbN Film Superconducting Coil with Cu plated layer of 42m in Length in a Spiral Three-Storied Trench Engraved in a Si Wafer of 76.2 mm in Diameter Formed by MEMS Technology for a Compact SMES with High Energy Storage Volume Density

Science.gov (United States)

Suzuki, Yasuhiro; Iguchi, Nobuhiro; Adachi, Kazuhiro; Ichiki, Akihisa; Hioki, Tatsumi; Hsu, Che-Wei; Sato, Ryoto; Kumagai, Shinya; Sasaki, Minoru; Noh, Joo-Hyong; Sakurahara, Yuuske; Okabe, Kyohei; Takai, Osamu; Honma, Hideo; Watanabe, Hideo; Sakoda, Hitoshi; Sasagawa, Hiroaki; Doy, Hideyuki; Zhou, Shuliang; Hori, H.; Nishikawa, Shigeaki; Nozaki, Toshihiro; Sugimoto, Noriaki; Motohiro, Tomoyoshi

2017-09-01

Based on the concept of a novel approach to make a compact SMES unit composed of a stack of Si wafers using MEMS process proposed previously, a complete fabrication of a traversable 3 µam thick NbN film superconducting coil lined with Cu plated layer of 42m in length in a spiral three-storied trench engraved in and extended over a whole Si-wafer of 76.2 mm in diameter was attained for the first time. With decrease in temperature, the DC resistivity showed a metallic decrease indicating the current pass was in the Cu plated layer and then made a sudden fall to residual contact resistance indicating the shift of current pass from the Cu plated layer to the NbN film at the critical temperature Tc of 15.5K by superconducting transition. The temperature dependence of I-V curve showed the increase in the critical current with decrease in the temperature and the highest critical current measured was 220 mA at 4K which is five times as large as that obtained in the test fabrication as the experimental proof of concept presented in the previous report. This completion of a one wafer superconducting NbN coil is an indispensable step for the next proof of concept of fabrication of series-connected two wafer coils via superconductive joint which will read to series connected 600 wafer coils finally, and for replacement of NbN by high Tc superconductor such as YBa2Cu3O7-x for operation under the cold energy of liquid hydrogen or liquid nitrogen.
Fractional flux excitations and flux creep in a superconducting film

International Nuclear Information System (INIS)

Lyuksyutov, I.F.

1995-01-01

We consider the transport properties of a modulated superconducting film in a magnetic field parallel to the film. Modulation can be either intrinsic, due to the layered structure of the high-T c superconductors, or artificial, e.g. due to thickness modulation. This system has an infinite set ( >) of pinned phases. In the pinned phase the excitation of flux loops with a fractional number of flux quanta by the applied current j results in flux creep with a generated voltage V ∝ exp[-jo/j[. (orig.)
Application of superconducting magnesium diboride (MGB2) in superconducting radio frequency cavities

Science.gov (United States)

Tan, Teng

The superconductivity in magnesium diboride (MgB2) was discovered in 2001. As a BCS superconductor, MgB2 has a record-high Tc of 39 K, high Jc of > 107 A/cm2 and no weak link behavior across the grain boundary. All these superior properties endorsed that MgB2 would have great potential in both power applications and electronic devices. In the past 15 years, MgB2 based power cables, microwave devices, and commercial MRI machines emerged and the next frontier are superconducting radio frequency (SRF) cavities. SRF cavities are one of the leading accelerator technologies. In SRF cavities, applied microwave power generates electrical fields that accelerate particle beams. Compared with other accelerator techniques, SRF cavity accelerators feature low loss, high acceleration gradients and the ability to accelerate continuous particle beams. However, current SRF cavities are made from high-purity bulk niobium and work at 2 K in superfluid helium. The construction and operational cost of SRF cavity accelerators are very expensive. The demand for SRF cavity accelerators has been growing rapidly in the past decade. Therefore, a lot of effort has been devoted to the enhancement of the performance and the reduction of cost of SRF cavities. In 2010, an acceleration gradient of over 50 MV/m has been reported for a Nb-based SRF cavity. The magnetic field at the inner surface of such a cavity is ~ 1700 Oe, which is close to the thermodynamic critical field of Nb. Therefore, new materials and technologies are required to raise the acceleration gradient of future SRF cavity accelerators. Among all the proposed approaches, using MgB2 thin films to coat the inner surface of SRF cavities is one of the promising tactics with the potential to raise both the acceleration gradient and the operation temperature of SRF cavity accelerators. In this work, I present my study on MgB2 thin films for their application in SRF cavities. C-epitaxial MgB2 thin films grown on SiC(0001) substrates
High Tc superconductors at microwave frequencies

International Nuclear Information System (INIS)

Gruener, G.

1991-01-01

The author discusses various experiments conducted in the micro- and millimeter wave spectral range on thin film and single crystal specimens of the high temperature oxide superconductors. For high quality film the surface resistance R s is, except at low temperatures, due to thermally excited carriers, with extrinsic effects playing only a secondary role. Because of the low loss various passive microwave components, such as resonators, delay lines and filters, with performance far superior to those made of normal metals can be fabricated. The conductivity measured at millimeter wave frequencies displays a peak below T c . Whether this is due to coherence factors or due to the change of the relaxation rate when the materials enter the superconducting state remains to be seen
Y-Ba-Cu-O superconducting film on oxidized silicon

International Nuclear Information System (INIS)

Gupta, R.P.; Khokle, W.S.; Dubey, R.C.; Singhal, S.; Nagpal, K.C.; Rao, G.S.T.; Jain, J.D.

1988-01-01

We report thick superconducting films of Y-Ba-Cu-O on oxidized silicon substrates. The critical temperatures for onset and zero resistance are 96 and 77 K, respectively. X-ray diffraction analysis predicts 1, 2, 3 composition and orthorhombic phase of the film
High-temperature superconducting phase of HBr under pressure predicted by first-principles calculations

Science.gov (United States)

Gu, Qinyan; Lu, Pengchao; Xia, Kang; Sun, Jian; Xing, Dingyu

2017-08-01

The high pressure phases of HBr are explored with an ab initio crystal structure search. By taking into account the contribution of zero-point energy (ZPE), we find that the P 4 /n m m phase of HBr is thermodynamically stable in the pressure range from 150 to 200 GPa. The superconducting critical temperature (Tc) of P 4 /n m m HBr is evaluated to be around 73 K at 170 GPa, which is the highest record so far among binary halogen hydrides. Its Tc can be further raised to around 95K under 170 GPa if half of the bromine atoms in the P 4 /n m m HBr are substituted by the lighter chlorine atoms. Our study shows that, in addition to lower mass, higher coordination number, shorter bonds, and more highly symmetric environment for the hydrogen atoms are important factors to enhance the superconductivity in hydrides.
High-Tc superconductor quantum interference devices

International Nuclear Information System (INIS)

1991-01-01

This patent describes a superconductive quantum interferometric device for sensing a characteristic of a magnetic field. It comprises a substrate having a surface, the substrate being selected from the group which consists of strontium titanate, aluminum oxide, sapphire, ZrO 2 and mixtures thereof; a coating of MgO on the surface of the substrate; two identical thin-strip films of a high-critical temperature superconductor on the coating, each of the films having a pair of mutually parallel arms in the form of superconductor strips extending toward and aligned with super conductor strips forming corresponding arms of the other thin-strip film, and a crossbar strip connecting the arms of each thin-strip film at right angles to the arms, the high-critical-temperature superconductor being selected from the group which consists of yttrium-barium-calcium-copper-oxides, bismuth-strontium-calcium-copper-oxides, thallium-barium-copper-oxides, thallium-barium-calcium-copper-oxides, barium oxide: potassium oxide: bismuth oxides, and calcium oxide: zinc oxide: iron oxides; and insulating films on the coating between corresponding free ends of the arms thin-strip films, the insulating films being composed of a material selected from the group which consists of silicon dioxide, silicon nitride, magnesium oxide and mixture thereof
Stoichiometry and superconductive properties of YBaCuO films deposited by spray pyrolysis

International Nuclear Information System (INIS)

Conde-Gallardo, A.; Falcony, C.; Ortiz, A.

1994-01-01

The dependence of the stoichiometry and the superconducting characteristics of YBaCuO films deposited by spray pyrolysis on the spraying solution composition and the deposition conditions is reported. It has been found that a proper optimization of the starting materials concentration in the spraying solution results in superconducting films with zero resistance temperature of 91 K and a transition to superconducting state within a 3 K range. X-ray diffraction and resistance vs temperature measurements have been used to monitor the crystal composition and the conductive characteristics of the films as a function of the spraying solution composition and the deposition parameters
Ferromagnetic film on a superconducting substrate

International Nuclear Information System (INIS)

Bulaevskii, L. N.; Chudnovsky, E. M.

2001-01-01

We study the equilibrium domain structure and magnetic flux around a ferromagnetic film with perpendicular magnetization M 0 on a superconducting (SC) substrate. At 4πM 0 c1 the SC is in the Meissner state and the equilibrium domain width in the film, l, scales as (l/4πλ L )=(l N /4πλ L ) 2/3 with the domain width on a normal (nonsuperconducting) substrate, l N /4πλ L >>1; λ L being the London penetration length
Superconductivity: Is there a problem in transuranics?

International Nuclear Information System (INIS)

Colineau, Eric; Griveau, Jean-Christophe; Eloirdi, Rachel; Hen, Amir; Caciuffo, Roberto

2014-01-01

Superconductivity was first reported in 1942 for uranium metal (¡-U) and in 1958 for U compounds: UCo, U6Mn, U6Fe, and U6Co, with critical temperatures Tc, of 1.7, 2.3, 3.9, and 2.3K, respectively. A new class of U superconductors emerged in the early 1980’s with the discovery of U heavy fermion superconductors : UBe13 (Tc = 0.85K), UPt3 (Tc = 0.53K), URu2Si2 (Tc = 1.5K) , UPd2Al3 (Tc = 1.9K) … Furthermore, in most of these systems, the superconducting phases coexist with antiferromagnetic (AF) correlations which have characteristic temperatures, usually the Néel temperature TN, that are typically one order of magnitude greater than the corresponding superconducting critical temperatures Tc. Superconductivity was even shown to co-exist with ferromagnetism in e.g. UGe2 (Tc ï» 0.8K, TC ï» 30K at p ï» 1.2GPa) and URhGe (Tc = 0.25K, TC = 9.5K). Heavy fermion superconductors still remain a major challenge for condensed matter physics. The existence of heavy fermion superconductivity and its coexistence or proximity with magnetic order suggests that the conventional mechanism of phonon-mediated superconductivity is inappropriate and that alternative mechanisms, like spin fluctuations, should be considered for Cooper pairing

High-Tc superconducting antenna-coupled microbolometer on silicon

Science.gov (United States)

Rice, Joseph P.; Grossman, Erich N.; Borcherdt, L. J.; Rudman, D. A.

1994-05-01

A process is described for fabricating antenna-coupled resistive-edge microbolometers based on the high-Tc superconductor YBa2Cu3O7 (YBCO) on silicon. The YBCO and a buffer layer of yttria-stabilized zirconia (YSZ) were grown epitaxially on silicon to minimize excess electrical noise. A silicon-micromachined YBCO/YSZ air-bridge was incorporated to minimize the thermal conductance and the heat capacity. The thermal conductance of the air-bridge was measured to be 3 X 10-6 W/K at a temperature of 100 K. At an operating temperature of 89 K, the detector is estimated to have a response time of 2 microsecond(s) , a responsivity of the 1000 V/W range, and a noise-equivalent power in the 10-12 W/Hz1/2 range at 1000 Hz.
Superconducting properties of the hexagonal-close-packed alloy system TcZr

International Nuclear Information System (INIS)

Chatterjee, P.

1984-01-01

The theoretical formula of McMillan, modified via the multiple-scattering theory of Gomersall and Gyorffy, is very successful in computing the electron-phonon coupling constant (lambda) and the superconducting transition temperature (T/sub c/) of elements and compounds from quantities readily obtainable from band structure work or approaches based on the scattering theory. However, for disordered solids this theory fails because of the breakdown of the translational symmetry used in the multiple scattering theory. In the particular case of substitutional alloys, the problem can still be solved however if, at each lattice point, the t-matrix of an individual scatterer is replaced by a configurational average of the t-matrices of the alloying materials (average t-matrix approximation). This modified theory, which has already been successfully applied to some cubic substitutional alloys, is herein used to predict lambda and T/sub c/ for the h.c.p. TcZr alloy system. The results indicate that this system has good superconducting properties. (author)
Growth and applications of superconducting Y-Ba-Cu-O thin films

International Nuclear Information System (INIS)

Pinto, R.

1991-01-01

This paper attempt to highlight the important PVD techniques such as evaporation, sputtering, ion beam deposition and excimer laser ablation for the preparation of superconducting YBaCuO thin films. Since enormous amount of work has been published over the last few years, this review is not comprehensive even in PVD techniques. In the area of applications for electronics, thin film appear to be much more promising than bulk high T c superconductors. Already high J c values in the region of 4 x 10 6 A cm -2 have been realized in thin films. Resonators and transmission lines have been fabricated using 123 films showing a transmission loss significantly lower than that of copper at 77 degrees K at X-band frequencies. This review will discuss some of the important electronic applications feasible with 123 films
Conventional proximity effect in bilayers of superconducting underdoped $La_{1.88}Sr_{0.12}CuO_4$ islands coated with non superconducting overdoped $La_{1.65}Sr_{0.35}CuO_4$

OpenAIRE

Koren, G.; Millo, O.

2009-01-01

Following a recent study by our group in which a large $T_c$ enhancement was reported in bilayers of the non-superconducting $La_{1.65}Sr_{0.35}CuO_4$ and superconducting $La_{1.88}Sr_{0.12}CuO_4$ films [Phys. Rev. Lett. \\textbf{101}, 057005 (2008)], we checked if a similar effect occurs when superconducting $La_{1.88}Sr_{0.12}CuO_4$ islands are coated with a continuous layer of the non superconducting $La_{1.65}Sr_{0.35}CuO_4$. We found that no such phenomenon is observed. The bare supercond...
An investigation in texturing high Tc superconducting ceramics by creep sintering

International Nuclear Information System (INIS)

Regnier, P.; Deschanels, X.; Maurice, F.; Schmirgeld, L.; Aguillon, C.; Senoussi, S.; Mac Carthy, M.; Tatlock, G.J.

1991-01-01

We study in detail the possibility of high-T c superconducting ceramics texturing by high pressing them during sintering. We show texture variations as a function of the applied load, of the deformation, of the temperature, and of the sintering stage length, of the rate of variation of temperature, of the material nature in contact with ceramic and of the original powder quality. We present results obtained by optical microscopy, electronic microscopy, X-rays, and local chemical analysis
Ferromagnetic film on a superconducting substrate

Energy Technology Data Exchange (ETDEWEB)

Bulaevskii, L. N.; Chudnovsky, E. M.

2001-01-01

We study the equilibrium domain structure and magnetic flux around a ferromagnetic film with perpendicular magnetization M{sub 0} on a superconducting (SC) substrate. At 4{pi}M{sub 0}film, l, scales as (l/4{pi}{lambda}{sub L})=(l{sub N}/4{pi}{lambda}{sub L}){sup 2/3} with the domain width on a normal (nonsuperconducting) substrate, l{sub N}/4{pi}{lambda}{sub L}>>1; {lambda}{sub L} being the London penetration length.
Experimental Observation of Non-'S-Wave' Superconducting Behavior in Bulk Superconducting Tunneling Junctions of Yba2Cu3O7-δ

Directory of Open Access Journals (Sweden)

Leandro Jose Guerra

1998-06-01

Full Text Available Evidence of non-s-wave superconductivity from normal tunneling experiments in bulk tunneling junctions of YBa2Cu3O7-δ is presented. The I-V and dI/dV characteristics of bulk superconducting tunneling junctions of YBa2Cu3O7-δ have been measured at 77.0K and clear deviation from s-wave superconducting behavior has been observed. The result agrees with d-wave symmetry, and interpreting the data in this way, the magnitude of the superconducting energy gap, 2Δ, is found to be (0.038 ± 0.002 eV. Comparing this energy gap with Tc (2Δ/kB Tc = 5.735, indicates that these high-Tc superconductors are strongly correlated materials, which in contrast with BCS-superconductors are believed to be weakly correlated.
Superconductivity in single wall carbon nanotubes

Directory of Open Access Journals (Sweden)

H Yavari

2009-08-01

Full Text Available By using Greens function method we first show that the effective interaction between two electrons mediated by plasmon exchange can become attractive which in turn can lead to superconductivity at a high critical temperature in a singl wall carbon nanotubes (SWCNT. The superconducting transition temperature Tc for the SWCNT (3,3 obtained by this mechanism agrees with the recent experimental result. We also show as the radius of SWCNT increases, plasmon frequency becomes lower and leads to lower Tc.
Characterization of superconducting coil for fault current limitation

International Nuclear Information System (INIS)

Polasek, Alexander; Dias, Rodrigo; Niedu, Daniel Brito; Ogasawara, Tsuneharu; Oliveira Filho, Orsino Borges de; Serra, Eduardo Torres; Gomes Junior, George; Amorim, Helio Salim

2010-01-01

The increasing power demand has been raising fault currents up to dangerous levels. Superconducting fault current limiters are a promising solution for this problem. In the present work, we studied a superconducting Bi-2212 coil that is used for fault current limitation. Samples were analyzed by XRD, SEM/EDS and measurement of critical temperature (Tc). The Rietveld method was employed for phase quantification. Relatively high Bi-2212 fractions were found. However, Tc varies from a sample to another one. Variations of local Tc are attributed to variations of oxygen content in Bi- 2212 phase. (author)
Upper critical field measurements in high-Tc superconducting oxides

Science.gov (United States)

Ousset, J. C.; Bobo, J. F.; Ulmet, J. P.; Rakoto, H.; Cheggour, N.

We present upper critical field measurements on the superconducting oxides RE Ba2Cu3O7-δ (RE = Y, Gd) performed in a pulsed magnetic field up to 43 T. Values for Hc2 as high as 52 T and 77 T for Y and Gd respectively, are expected at 77 K. However, in order to observe no resistive behaviour up to 43 T the temperature must be decreased down to 50 K. In the case of oxygen deficient systems the magnetoresistance reveals two superconducting phases wich could be related to two different orders of oxygen vacancies. Nous présentons des mesures de champ critique Hc2 sur les supraconducteurs TR Ba 2Cu3O7-δ (TR = Y, Gd) réalisées en champ magnétique pulsé jusqu'à 43 T. Elles permettent de prévoir des valeurs de H c2 de 52 T et 77 T respectivement pour Y et Gd à 77 K. Cependant, pour ne pas observer de comportement résistif jusqu'au champ maximum, il est nécessaire de refroidir l'échantillon jusqu'à 50 K. Dans le cas des systèmes déficients en oxygène (δ important) nous mettons en évidence l'existence de deux phases supraconductrices qui pourraient être dues à deux ordres différents des lacunes d'oxygène.
The design of high-Tc superconductors - Room-temperature superconductivity?

International Nuclear Information System (INIS)

Tallon, J.L.; Storey, J.G.; Mallett, B.

2012-01-01

This year is the centennial of the discovery of superconductivity and the 25th anniversary of the discovery of high-T c superconductors (HTS). Though we still do not fully understand how HTS work, the basic rules of design can be determined from studying their systematics. We know what to do to increase T c and, more importantly, what to do to increase critical current density J c . This in turn lays down a challenge for the chemist. Can the ideal design be synthesized? More importantly, what are the limits? Can one make a room-temperature superconductor? In fact fluctuations place strict constraints on this objective and provide important guidelines for the design of the ideal superconductor.
Abrupt onset of a second energy gap at the superconducting transition of underdoped Bi2212

Energy Technology Data Exchange (ETDEWEB)

Hussain, Zahid; Lee, W.S.; Vishik, I.M.; Tanaka, K.; Lu, D.H.; Sasagawa, T.; Nagaosa, N.; Devereaux, T.P.; Hussain, Z.; Shen, Z.-X.

2007-05-26

he superconducting gap--an energy scale tied to the superconducting phenomena--opens on the Fermi surface at the superconducting transition temperature (Tc) in conventional BCS superconductors. In underdoped high-Tc superconducting copper oxides, a pseudogap (whose relation to the superconducting gap remains a mystery) develops well above Tc (refs 1, 2). Whether the pseudogap is a distinct phenomenon or the incoherent continuation of the superconducting gap above Tc is one of the central questions in high-Tc research3, 4, 5, 6, 7, 8. Although some experimental evidence suggests that the two gaps are distinct9, 10, 11, 12, 13, 14, 15, 16, 17, 18, this issue is still under intense debate. A crucial piece of evidence to firmly establish this two-gap picture is still missing: a direct and unambiguous observation of a single-particle gap tied to the superconducting transition as function of temperature. Here we report the discovery of such an energy gap in underdoped Bi2Sr2CaCu2O8+delta in the momentum space region overlooked in previous measurements. Near the diagonal of Cu?O bond direction (nodal direction), we found a gap that opens at Tc and has a canonical (BCS-like) temperature dependence accompanied by the appearance of the so-called Bogoliubov quasi-particles, a classical signature of superconductivity. This is in sharp contrast to the pseudogap near the Cu?O bond direction (antinodal region) measured in earlier experiments19, 20, 21.
Anisotrophic currents and flux jumps in high-T-c superconducting films with self-organized arrays of planar defects

DEFF Research Database (Denmark)

Yurchenko, V.V.; Qviller, A.J.; Mozhaev, P.B.

2010-01-01

Regular arrays of planar defects with a period of a few nanometers can be introduced in superconducting YBa2Cu3O7-delta (YBCO) thin films by depositing them on vicinal (also called miscut or tilted) substrates. This results in the anisotropy of critical currents flowing in the plane of the film. ...
Generation of coherent electromagnetic radiation by superconducting films at nitrogen temperatures

CERN Document Server

Lykov, A N

2001-01-01

One detected generation of coherent electromagnetic radiation by GdBa sub 2 Cu sub 3 O sub 7 sub - sub x superconducting films within 1-10 MHz range at temperature of liquid nitrogen boiling. This type generation is caused by synchronization realized due to the feedback of abrupt changes of the Abrikosov's vortices produced by the external low-frequency magnetic field. Possibility to reach more intensive radiation due to increase of the area of superconducting film, as well as, via increase of amplitude and of frequency of electromagnetic field exciting a vortex system in films is the most important advantage of the given technique of generation
Preparation of YBCO superconducting films by spray pyrolysis method

International Nuclear Information System (INIS)

Mora Alonso, M.; Leyva Fabelo, A.; Rubio Frias, E.; Pupo Gonzalez, I.; Lopez Sanchez, D.

1994-01-01

The methodology for the preparation of YBCO superconducting films on Zr 2O (Y) substrates by spray pyrolysis method is reported. The transition temperature of these films is superior than the boiling temperature of liquid 2N . Other critical parameters are similar to those reported by other authors using the same technique
What is the role of Pb(II) in high Tc superconductors

International Nuclear Information System (INIS)

Raveau, B.; Hervieu, M.; Michel, C.; Groult, D.; Provost, J.

1990-01-01

An overview of the layered lead cuprates is presented here. The structure of these oxides and their non-stoichiometry are studied in connection with their superconducting properties. The phenomena involving a modulation of the structure, characterized by the presence of satellites on E.D. patterns are described and the particular role of the 6s 2 lone pair of Pb(II) is discussed. Divalent lead is, owing to its size intermediate between that of strontium and barium, a potential cation for superconductive cuprates. Moreover, this interest for Pb(II), is supported by its electronic structure which involves an electronic 6s 2 lone pair well known for its ability to form layered structures. In spite of these characteristics, few superconductive layered suprates were isolated at the beginning of the rush to high Tc superconductors. This is probably due to the possibility of existence of redox reactions involving the couple Pb(II)/Pb(IV), which require very particular experimental conditions. The authors report here on the recent development of the crystal chemistry of those materials and on their corresponding superconducting properties
Superconductivity

CERN Document Server

Ketterson, John B

2008-01-01

Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...
Models of high-Tc superconductivity and applications to electric generators and motors

DEFF Research Database (Denmark)

Sørensen, Mads Peter

We present the Ginzburg Landau model for mesoscopic high-Tc superconductors of complex geometry. It is shown that giant vortices can form at boundary defects. The relation between total magnetic flux penetration through the superconductor and the externally applied field is established. This is i...
Microwave Josephson generation in thin film superconducting bridges

International Nuclear Information System (INIS)

Gubankov, V.N.; Koshelets, V.P.; Ovsyannikov, G.A.

1975-01-01

Thin-film bridges have some advantage over other types of superconducting weak links: good definition of electromagnetic parameters and of weak region geometry. Up to now Josephson properties of bridges have been investigated by using indirect methods (the effect of magnetic field on the critical current I 0 , the bridge behavior in a microwave field, etc.). Direct experimental observation of Josephson radiation from autonomous thin film bridges is reported. Microwave radiation in tin bridges of 'variable' thickness has been investigated where the thickness of the film forming the bridge is far less than the thickness of the bank films. (Auth.)
High-{Tc} superconducting antenna-coupled microbolometer on silicon

Energy Technology Data Exchange (ETDEWEB)

Rice, J.P.; Grossman, E.N.; Borcherdt, L.J.; Rudman, D.A. [National Inst. of Standards and Technology, Boulder, CO (United States). Cryoelectronic Metrology Group

1994-12-31

A process is described for fabricating antenna-coupled resistive-edge microbolometers based on the high-{Tc} superconductor YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) on silicon. The YBCO and a buffer layer of yttria-stabilized zirconia (YSZ) were grown epitaxially on silicon to minimize excess electrical noise. A silicon-micromachined YBCO/YSZ air-bridge was incorporated to minimize the thermal conductance and the heat capacity. The thermal conductance of the air-bridge was measured to be 3 {times} 10{sup {minus}6} W/K at a temperature of 100 K. At an operating temperature of 89 K, the detector is estimated to have a response time of 2 {micro}s, a responsivity in the 1,000 V/W range, and a noise-equivalent power (NEP) in the 10{sup {minus}12} W/Hz{sup 1/2} range at 1,000 Hz.

Structural and superconducting properties of epitaxial Fe{sub 1+y}Se{sub 1-x}Te{sub x} thin films

Energy Technology Data Exchange (ETDEWEB)

Richter, Stefan; Yuan, Feifei; Grinenko, Vadim; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Sala, Alberto; Putti, Marina [Dipartimento di Fisica, Universita di Genova (Italy)

2015-07-01

The iron based superconductor Fe(Se,Te) is in the center of much ongoing research. The reason for this is on the one hand its simple crystal structure, that consists only of stacked Fe(Se,Te) layers so that structural and superconducting properties can be connected more easily, on the other hand FeSe itself shows a high sensibility for strain and changes in stoichiometry and can have potentially very high critical temperatures under hydrostatic pressure or in monolayers. We investigate epitaxial thin films of Fe{sub 1+y}Se{sub 1-x}Te{sub x} grown by pulsed laser deposition on different single crystalline substrates. A high crystalline quality and a superconducting transition of up to about 20 K can be achieved using optimized deposition parameters. The influence of growth conditions, Te-doping, film thickness and post growth oxygen treatment on the structural and superconducting properties on these films will be presented in detail.
Superconductivity at 43K in SmFeAsO1-xFx

Science.gov (United States)

Chen, X. H.; Wu, T.; Wu, G.; Liu, R. H.; Chen, H.; Fang, D. F.

2008-06-01

Since the discovery of high-transition-temperature (high-Tc) superconductivity in layered copper oxides, extensive effort has been devoted to exploring the origins of this phenomenon. A Tc higher than 40K (about the theoretical maximum predicted from Bardeen-Cooper-Schrieffer theory), however, has been obtained only in the copper oxide superconductors. The highest reported value for non-copper-oxide bulk superconductivity is Tc = 39K in MgB2 (ref. 2). The layered rare-earth metal oxypnictides LnOFeAs (where Ln is La-Nd, Sm and Gd) are now attracting attention following the discovery of superconductivity at 26K in the iron-based LaO1-xFxFeAs (ref. 3). Here we report the discovery of bulk superconductivity in the related compound SmFeAsO1-xFx, which has a ZrCuSiAs-type structure. Resistivity and magnetization measurements reveal a transition temperature as high as 43K. This provides a new material base for studying the origin of high-temperature superconductivity.
The Effect of Twins on Critical Currents of High Tc Superconductors

Science.gov (United States)

1989-01-01

particles to stick together due to electrostatic forces. To overcome this we have formed a slurry of the material in liquid nitrogen and flash...can use and the liquid convection tends to counteract the separation process. We have-now designed a magnetic track which particles will slide down with...Currents of High Tc Superconductors" - A.M. Campbell and M.F. Ashby The initial work on levitation forces and separation of superconducting powders has
Nanoscale wedge polishing of superconducting thin films-an easy way to obtain depth dependent information by surface analysis techniques

International Nuclear Information System (INIS)

Shapoval, T; Engel, S; Gruendlich, M; Meier, D; Backen, E; Neu, V; Holzapfel, B; Schultz, L

2008-01-01

A mechanical wedge polishing procedure that offers a simple, cost-effective and rapid way to look into the depth of a thin film with different surface-sensitive scanning techniques has been developed. As an example of its wide applicability, this method was utilized for the investigation of two differently prepared superconducting YBa 2 Cu 3 O 7-δ thin films: an Hf-doped film prepared by chemical solution deposition and an undoped film grown by pulsed laser deposition. Upon polishing, the roughness of the samples was reduced to less than 5 nm (peak-to-valley) without influencing the superconducting properties of the films. Thus, nanoscale polishing opens up a unique possibility for microscopic studies with various surface-sensitive techniques. We demonstrate the successful imaging of flux lines by low temperature magnetic force microscopy after polishing a formerly rough as-prepared film. By applying the wedge polishing procedure to the Hf-doped sample, high resolution electron backscattering diffraction investigations reveal the homogeneous distribution of non-superconducting BaHfO 3 nanoparticles in the whole volume of the film
JETC (Japanese Technology Evaluation Center) Panel Report on High Temperature Superconductivity in Japan

Science.gov (United States)

Shelton, Duane; Gamota, George

1989-01-01

The Japanese regard success in R and D in high temperature superconductivity as an important national objective. The results of a detailed evaluation of the current state of Japanese high temperature superconductivity development are provided. The analysis was performed by a panel of technical experts drawn from U.S. industry and academia, and is based on reviews of the relevant literature and visits to Japanese government, academic and industrial laboratories. Detailed appraisals are presented on the following: Basic research; superconducting materials; large scale applications; processing of superconducting materials; superconducting electronics and thin films. In all cases, comparisons are made with the corresponding state-of-the-art in the United States.
A novel selenization technique for fabrication of superconducting FeSex thin film

International Nuclear Information System (INIS)

Chai Qinglin; Tu Hailing; Hua Zhiqiang; Wang Lei; Qu Fei

2011-01-01

A novel selenization technique was applied to prepare superconducting FeSe x films with pre-set FeS films. The combination of reactive sputtering deposition with elemental diffusion technique would extend to prepare films of other iron-based superconductors. The results of transport measurement got close or greater than that of previous reports. T c,onset and T c,0 got to 10.2 K and 4 K respectively. We believe that increase of the content of Fe 7 Se 8 could not only reduce T c but also slow down the decline of resistivity. A combinative method with reactive sputtering deposition and selenization technique was applied to prepare superconducting FeSe x films on LaAlO 3 substrates successfully. The influence of selenizing temperature on film components was studied. FeSe 0.96 and FeSe films had similar and good performances in transport measurement but little difference in magnetic property. The critical onset temperature got to 11.2 K and T c,0 got to 4 K approximately. X-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy were used to analyze the ratio of constituents and morphology of several selenized films. FeSe x film had a porous structure on surface and no well preferred orientation, which were confirmed to have little influence on superconducting properties.
Intrinsic and experimental quasiparticle recombination times in superconducting films

International Nuclear Information System (INIS)

Eisenmenger, W.; Lassmann, K.; Trumpp, H.J.; Krauss, R.

1977-01-01

Experimental quasiparticle recombination lifetime data for superconducting Al, Sn, and Pb films are compared with calculations based on a ray acoustic model taking account of the film thickness dependence of the reabsorption of recombination phonons. Information on the true or intrinsic quasiparticle recombination lifetime obtained from these and other data is discussed. (orig.) [de
Comment on ``Ferromagnetic film on a superconducting substrate''

Science.gov (United States)

Sonin, E. B.

2002-10-01

A superconducting substrate is not able to shrink drastically domains in a ferromagnetic film, contrary to the prediction of Bulaevskii and Chudnovsky. This is shown on the basis of the exact solution for the stripe domain structure.
Rotational loss of a ring-shaped flywheel supported by high Tc superconducting levitation

International Nuclear Information System (INIS)

Teshima, Hidekazu; Tawara, Taichi; Shimada, Ryuichi.

1997-01-01

This paper describes the experimental results for the rotational loss of a ring-shaped flywheel supported by high T c superconducting levitation. Superconducting levitation is appropriate for rotating a ring-shaped flywheel which has neither shaft nor hub because it is a non-contact and automatically stable levitation without any control systems. The rotational loss has been investigated using a small-scaled experimental machine consisting of 16 bulk superconductors 46 mm in diameter and a ring-shaped flywheel about 300 mm in diameter. The rotational loss decreased as the levitation gap height increased. In low-speed rotational regions, the rotational loss was in proportion to the rotation speed and depended more on the levitation gap. In high-speed rotational regions, the rotational loss was in proportion to the third power of the rotation speed and depended less on the levitation gap. The cubic rotational loss in He was reduced to one-fifth of that in air. The magnetic field pinned in bulk superconductors induces a loss in the materials composing the ring-shaped flywheel. The rotational loss of a ring-shaped flywheel supported by superconducting levitation can be reduced by improving the uniformity of the magnetic fields along the ring, enlargement of the bulk superconductor(s), and densely arranging the bulk superconductors. (author)
Direct observation of competition between superconductivity and charge density wave order in YBa2Cu3O6.67

DEFF Research Database (Denmark)

Chang, J.; Blackburn, E.; Holmes, A. T.

2012-01-01

Superconductivity often emerges in the proximity of, or in competition with, symmetry-breaking ground states such as antiferromagnetism or charge density waves (CDW). A number of materials in the cuprate family, which includes the high transition-temperature (high-Tc) superconductors, show spin...... and charge density wave order. Thus a fundamental question is to what extent do these ordered states exist for compositions close to optimal for superconductivity. Here we use high-energy X-ray diffraction to show that a CDW develops at zero field in the normal state of superconducting YBa2Cu3O6.67 (Tc= 67 K......). This sample has a hole doping of 0.12 per copper and a well-ordered oxygen chain superstructure. Below Tc, the application of a magnetic field suppresses superconductivity and enhances the CDW. Hence, the CDW and superconductivity in this typical high-Tc material are competing orders with similar energy...
Superconductivity: materials and applications; La supraconductivite: materiaux et apllications

Energy Technology Data Exchange (ETDEWEB)

Duchateau, J.L. [CEA Cadarache, 13 - Saint Paul lez Durance (France); Kircher, F. [CEA Saclay, 91 - Gif sur Yvette (France); Leveque, J. [Groupe de Recherche en Electrotechnique et Electronique de Nancy, GREEN - UHP, 54 - Vandoeuvre les Nancy (France); Tixador, P. [INP/Institut Neel, 38 - Grenoble (France)

2008-07-01

This digest paper presents the different types of superconducting materials: 1 - the low-TC superconductors: the multi-filament composite as elementary constituent, the world production of NbTi, the superconducting cables of the LHC collider and of the ITER tokamak; 2 - the high-TC superconductors: BiSrCaCuO (PIT 1G) ribbons and wires, deposited coatings; 3 - application to particle physics: the the LHC collider of the CERN, the LHC detectors; 4 - applications to thermonuclear fusion: Tore Supra and ITER tokamaks; 5 - NMR imaging: properties of superconducting magnets; 6 - applications in electrotechnics: cables, motors and alternators, current limiters, transformers, superconducting energy storage systems (SMES). (J.S.)
Superconducting Ferromagnetic Nanodiamond.

Science.gov (United States)

Zhang, Gufei; Samuely, Tomas; Xu, Zheng; Jochum, Johanna K; Volodin, Alexander; Zhou, Shengqiang; May, Paul W; Onufriienko, Oleksandr; Kačmarčík, Jozef; Steele, Julian A; Li, Jun; Vanacken, Johan; Vacík, Jiri; Szabó, Pavol; Yuan, Haifeng; Roeffaers, Maarten B J; Cerbu, Dorin; Samuely, Peter; Hofkens, Johan; Moshchalkov, Victor V

2017-06-27

Superconductivity and ferromagnetism are two mutually antagonistic states in condensed matter. Research on the interplay between these two competing orderings sheds light not only on the cause of various quantum phenomena in strongly correlated systems but also on the general mechanism of superconductivity. Here we report on the observation of the electronic entanglement between superconducting and ferromagnetic states in hydrogenated boron-doped nanodiamond films, which have a superconducting transition temperature T c ∼ 3 K and a Curie temperature T Curie > 400 K. In spite of the high T Curie , our nanodiamond films demonstrate a decrease in the temperature dependence of magnetization below 100 K, in correspondence to an increase in the temperature dependence of resistivity. These anomalous magnetic and electrical transport properties reveal the presence of an intriguing precursor phase, in which spin fluctuations intervene as a result of the interplay between the two antagonistic states. Furthermore, the observations of high-temperature ferromagnetism, giant positive magnetoresistance, and anomalous Hall effect bring attention to the potential applications of our superconducting ferromagnetic nanodiamond films in magnetoelectronics, spintronics, and magnetic field sensing.
Nb3Ge superconductive films grown with nitrogen

International Nuclear Information System (INIS)

Sigsbee, R.A.

1978-01-01

A superconductive film of Nb 3 Ge is produced by providing within a vacuum chamber a heated substrate and sources of niobium and germanium, reducing the pressure within the chamber to a residual pressure no greater than about 10 -5 mm Hg, introducing nitrogen into the resulting evacuated chamber in controlled amounts and vaporizing the niobium and germanium to deposit a film of Nb 3 Ge on the heated substrate
Molecular-Beam Epitaxially Grown MgB2 Thin Films and Superconducting Tunnel Junctions

Directory of Open Access Journals (Sweden)

Jean-Baptiste Laloë

2011-01-01

Full Text Available Since the discovery of its superconducting properties in 2001, magnesium diboride has generated terrific scientific and engineering research interest around the world. With a of 39 K and two superconducting gaps, MgB2 has great promise from the fundamental point of view, as well as immediate applications. Several techniques for thin film deposition and heterojunction formation have been established, each with its own advantages and drawbacks. Here, we will present a brief overview of research based on MgB2 thin films grown by molecular beam epitaxy coevaporation of Mg and B. The films are smooth and highly crystalline, and the technique allows for virtually any heterostructure to be formed, including all-MgB2 tunnel junctions. Such devices have been characterized, with both quasiparticle and Josephson tunneling reported. MgB2 remains a material of great potential for a multitude of further characterization and exploration research projects and applications.
Direct growth of superconducting NdFeAs(O,F) thin films by MBE

Energy Technology Data Exchange (ETDEWEB)

Chihara, Masashi, E-mail: chihara@iku.xtal.nagoya-u.ac.jp [Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Sumiya, Naoki; Arai, Kenta [Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Ichinose, Ataru; Tsukada, Ichiro [Central Research Institute of Electric Power Industry, Yokosuka-shi, Kanagawa 240-0101 (Japan); Hatano, Takafumi; Iida, Kazumasa; Ikuta, Hiroshi [Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan)

2015-11-15

Highlights: • Highly textured NdFeAs(O,F) thin films were obtained by a direct growth method. • Enhancing the migration was crucial to realize the direct growth. • The critical current density exceeded 3 MA/cm{sup 2} at self-field and 1 MA/cm{sup 2} at 9 T. • A two-dimensional growth was confirmed by the observation of surface morphology. - Abstract: We report on the growth of NdFeAs(O,F) superconducting thin films by molecular beam epitaxy without having a NdOF secondary layer that was necessary for fluorine doping in our previous studies. The key to realizing the direct growth of a superconducting film was the enhancement of migration of the raw materials on the substrate, which was accomplished by two steps. Firstly, we increased the growth temperature that improved the crystalline quality of parent NdFeAsO thin films. Secondly, the atmosphere in the chamber during the growth was improved by changing the crucible material of the Fe source cell. Highly textured NdFeAs(O,F) thin films with critical temperatures up to 50 K were obtained, and terraces were observed by atomic force microscope, indicating a two-dimensional growth. However, precipitates were also found on the surface, which suggests that enhancing further the migration is necessary for obtaining a NdFeAs(O,F) thin film with a better quality.
Micropatterned superconducting film circuitry for operation in hybrid quantum devices

International Nuclear Information System (INIS)

Bothner, Daniel

2013-01-01

This thesis discusses three aspects of the arduous way towards hybrid quantum systems consisting of superconducting circuits and ensembles of ultracold paramagnetic atoms. In the first part of the thesis, superconducting coplanar microwave resonators as used for quantum information processing with superconducting qubits are investigated in magnetic fields. In the second part of the thesis integrated atom chips are designed and fabricated, which offer the possibility to trap an ensemble of ultracold atoms close to a superconducting coplanar resonator on that chip. In the third and last part of the thesis, unconventional disordered and quasiperiodic arrangements of microfabricated holes (antidots) in superconducting films are patterned and investigated with respect to the impact of the arrangement on the superconductor transport properties in magnetic fields.
Feshbach shape resonance for high Tc superconductivity in superlattices of nanotubes

International Nuclear Information System (INIS)

Bianconi, Antonio

2006-01-01

The case of a Feshbach shape resonance in the pairing mechanism for high T c superconductivity in a crystalline lattice of doped metallic nanotubes is described. The superlattice of doped metallic nanotubes provides a superconductor with a strongly asymmetric gap. The disparity and different spatial locations of the wave functions of electrons in different subbands at the Fermi level should suppress the single electron impurity interband scattering giving multiband superconductivity in the clean limit. The Feshbach resonances will arise from the component single-particle wave functions out of which the electron pair wave function is constructed: pairs of wave functions which are time inverse of each other. The Feshbach shape resonance increases the critical temperature by tuning the chemical potential at the Lifshitz electronic topological transition (ETT) where the Fermi surface of one of the bands changes from the one dimensional (1D) to the two dimensional (2D) topology (1D/2D ETT). (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)
Superconducting TlCa2Ba2Cu3O9 thick films

International Nuclear Information System (INIS)

1994-01-01

GE Corporate Research and Development's (GE-CRD) program to develop the two-zone silver addition (TZSA) process for fabricating superconducting films of TlCa 2 Ba 2 Cu 3 O 9 has activities in the areas of (1) precursor preparation, (2) the thallium oxide vapor process, (3) the effects of post-synthesis annealing ambient and temperature on superconducting properties, (4) the influence of film stoichiometry and composition on superconducting properties, (5) microstructure and film growth mechanism, (6) the preparation of thicker films, (7) the fabrication of films on flexible substrates, and (8) process scale-up. As part of its effort under the ANL Pilot Center Agreement, GE-CRD has supplied to ANL a complete two-zone furnace, has provided consultation on its use and on the planning of experiments, has processed ANL samples in GE's furnaces to help define optimum process conditions, and has provided precursor and finished films as requested. These contributions are described more fully in the descriptions of the work performed at ANL presented elsewhere in this report. Under the Pilot Center Agreement work at GE-CRD has been directed toward the optimization of the TZSA process with emphasis on (A) process improvement, (B) effects of silver content on film properties, (C) the relationship between microstructure and J c , and (D) toward the assessment of the compatibility of silver substrates with the process chemistry
Levitation properties of a ring-shaped flywheel supported by high Tc superconducting levitation

International Nuclear Information System (INIS)

Teshima, Hidekazu; Tawara, Taichi; Shimada, Ryuichi.

1997-01-01

In this paper we propose a new combination of high T c superconducting levitation and ring-shaped flywheel energy storage systems. Superconducting levitation is appropriate for rotating a ring-shaped flywheel which has neither shaft nor hub, because it is a non-contact and automatically stable levitation without any control systems. The levitation properties such as static and dynamic lateral stiffnesses, lateral damping, and lateral vibration during rotation have been investigated using a small-scaled experimental machine consisting of 16 bulk superconductors 46 mm in diameter and a ring-shaped flywheel about 300 mm in diameter. The spring constant increased as the levitation gap height decreased, and the dynamic spring constant was slightly higher than the static constant. The damping coefficient increased as the gap height decreased and the vibration amplitude increased. The experimental critical speed was in good agreement with the calculated one using a one-degree of freedom model. Finally, the possibility of large-scaled practical systems is discussed from the viewpoint of superconducting levitation. (author)
Superconductivity in nanostructured lead

Science.gov (United States)

Lungu, Anca; Bleiweiss, Michael; Amirzadeh, Jafar; Saygi, Salih; Dimofte, Andreea; Yin, Ming; Iqbal, Zafar; Datta, Timir

2001-01-01

Three-dimensional nanoscale structures of lead were fabricated by electrodeposition of pure lead into artificial porous opal. The size of the metallic regions was comparable to the superconducting coherence length of bulk lead. Tc as high as 7.36 K was observed, also d Tc/d H was 2.7 times smaller than in bulk lead. Many of the characteristics of these differ from bulk lead, a type I superconductor. Irreversibility line and magnetic relaxation rates ( S) were also studied. S( T) displayed two maxima, with a peak value about 10 times smaller than that of typical high- Tc superconductors.

New Methods for Thin Film Deposition and First Investigations of the use of High Temperature Superconductors for Thin Film Cavities

CERN Document Server

Gustafsson, Anna; Vollenberg, Wilhelmus; Seviour, Rebecca

2010-01-01

Niobium thin film cavities have shown good and reliable performance for LEP and LHC, although there are limitations to overcome if this technique should be used for new accelerators such as the ILC. New coating techniques like High Power Impulse Magnetron Sputtering (HiPIMS) has shown very promising results and we will report on its possible improvements for Nb thin film cavity performance. Current materials used in accelerator Superconducting Radio Frequency (SRF) technologies operate at temperatures below 4 K, which require complex cryogenic systems. Researchers have investigated the use of High Temperature Superconductors (HTS) to form RF cavities, with limited success. We propose a new approach to achieve a high-temperature SRF cavity based on the superconducting ’proximity effect’. The superconducting proximity effect is the effect through which a superconducting material in close proximity to a non-superconducting material induces a superconducting condensate in the latter. Using this effect we hope...
Observation of magnetooptical effects in several high Tc superconductors

International Nuclear Information System (INIS)

Dillon, J.F. Jr; Lyons, K.B.

1992-01-01

Recent so called 'anyon' theories of high temperature superconductivity in layer structure materials suggested that at some temperature T TP ≥T c there is a symmetry breaking transition below which these materials may be in either of two distinct states related to each other by time reversal. The study of magneto-optical effects in superconductors reviewed here was undertaken to explore time reversal symmetry of these materials. Using novel technique with rotating λ/2 plate at 525 nm, 'circular dichroism' was observed on reflection from epitaxial films and single crystals of cuprate superconductor with layer structures. The onset of dichroism was at temperatures of ∼ 180K to ∼ 300K. These results appear to support the 'anyon' theories. However, circular dichroism was also seen in films and single crystals of bismuthate superconductors with cubic structure, to which the theories seem inapplicable. In sharp contrast, Spielman et al., at Stanford in a very sensitive experiment at 1060 nm have seen no evidence of non-reciprocal circular birefringence in epitaxial cuprate superconducting films. Weber et al. at Dortmund have recently reported the observation at 633 nm of non-reciprocal magneto-optical effects on single crystals of cuprate superconductors, but none on films. (author). 15 refs., 5 figs
Electronic components with yttrium- and bismuth-based high-Tc superconductors

International Nuclear Information System (INIS)

Daginnus, M.; Guettler, B.

1992-01-01

This project investigates the fabrication of microwave components by use of high-Tc superconductors. Detailed descriptions are given of the manufacturing and use of active Y-Ba-Cu-O components. The surface resistance of thin films used in high-quality passive microwave components such as resonators and filters is measured and optimized. (orig./MM) [de
Critical current densities amd pinning mechanisms of high-Tc films on single crystalline and technologically relevant substrates. Final report

International Nuclear Information System (INIS)

Adrian, H.

1995-12-01

The report deals with six project tasks: (1) Effects of impurity additions at atomic level on the pinning behaviour and the critical current densities, examined in epitactic YBA 2 (Cu 1-x Ni x ) 3 O 7 films. It could be proven that the Ni atoms increase the activation energy for flux movement and the critical current density in a concentration range of 0 2 Sr 2 Ca n-1 Cu n O 2n+4+δ films (n = 2 and 3) with good crystalline properties, high critical currents, and high current densities were prepared. Thin YBa 2 Cu 3 O 7 films of high quality could be grown on saphire substrates, both by the MO-CVD process and by MBE. The aim of depositing biaxially textured YBa 2 Cu 3 O 7 films with high critical current densities on polycrystalline, metallic substrates was achieved by the IBAD process combined with MBE. The buffer layer was YSZ. Heterostructures of the layer sequence YBa 2 Cu 3 O 7 /CeO 2 /Y 0.3 Pr 0.7 Ba 2 Cu 3 O 7 /YBa 2 Cu 3 O 7 and YBa 2 Cu 3 O 7 /CeO 2 /Au were prepared by laser ablation and sputtering processes, in order to examine Josephson ramp contacts and superconducting field-effect transistors. (orig./MM) [de
Disorder and fluctuations in superconducting YBa2Cu3O6.9 films

International Nuclear Information System (INIS)

Gauzzi, A.

1993-01-01

We have developed the technique of ion-beam sputtering to grow thin (∼ 100 nm) superconducting YBa 2 Cu 3 O 6.9 (YBCO) films. We demonstrate that this technique is suitable for the in-situ deposition at low temperatures ( o C) of uniform films over large areas (≤30 cm 2 ). We found that preferential sputtering effects disappear if low-power ions-beams are used, thus enabling the control of the 1:2:3 composition by using a single stoichiometric target. We have found that the disorder in the crystal, introduced by too high or too low growth temperatures, affects strikingly both, the superconducting and the transport properties of the films. We report evidence that disorder on the atomic scale plays a role equivalent to oxygen doping. The similarity observed between the effects of crystal disorder in our films and the effects of oxygen depletion or Co-doping reported in the literature suggests that the disorder affects mainly the CuO chains. This implies that the local order of the chains controls not only the superconducting properties, as already established in the literature, but also the transport of the carriers in the normal state. Finally, we have investigated the local character of the superconducting state of YBCO by studying the paraconductivity in our films. We have found no indication of critical fluctuations at temperatures ≥5 mK above the zero-resistance critical temperature. Our analysis indicates that the spectrum of mean-field fluctuations is dominated by short-wavelength components and is affected by disorder. As a consequence, the temperature dependence of the critical exponents becomes complex and deviates from the universal predictions of conventional theories. We have explained quantitatively our experimental data and clarified the controversy existing in the literature by using a three-dimensional cut-off approach applied to the Lorentzian spectrum of the Ginzburg-Landau theory. (author) figs., tabs., refs
Highly oriented as-deposited superconducting laser ablated thin films of Y1Ba2Cu3O/sub 7-//sub δ/ on SrTiO3, zirconia, and Si substrates

International Nuclear Information System (INIS)

Koren, G.; Polturak, E.; Fisher, B.; Cohen, D.; Kimel, G.

1988-01-01

KrF excimer laser ablation of an Y 1 Ba 2 Cu 3 O/sub 7-//sub δ/ pellet in 0.1--0.2 Torr of O 2 ambient was used to deposit thin superconducting films onto SrTiO 3 , yttria-stabilized zirconia (YSZ), and silicon substrates at 600--700 0 C. The as-deposited 1-μm-thick films at 650--700 0 C substrate temperature were superconducting, without further high-temperature annealing. All films had a similar T/sub c/ onset of ∼92 K but different zero-resistance T/sub c/ of 90, 85, and 70 K for the films on SrTiO 3 , YSZ, and Si substrates, respectively. Angular x-ray diffraction analysis showed that all the films were highly oriented with the c axis perpendicular to their surface. Critical current densities at 77 K were about 40 000 and 10 000 A/cm 2 for the films on SrTiO 3 and YSZ, respectively. Smooth surface morphology was observed in all films, with occasional defects and cracks in the films on YSZ, which seems to explain the lower critical current in these films
Comparative Review on Thin Film Growth of Iron-Based Superconductors

Directory of Open Access Journals (Sweden)

Yoshinori Imai

2017-07-01

Full Text Available Since the discovery of the novel iron-based superconductors, both theoretical and experimental studies have been performed intensively. Because iron-based superconductors have a smaller anisotropy than high-Tc cuprates and a high superconducting transition temperature, there have been a lot of researchers working on the film fabrication of iron-based superconductors and their application. Accordingly, many novel features have been reported in the films of iron-based superconductors, for example, the fabrication of the epitaxial film with a higher Tc than bulk samples, the extraction of the metastable phase which cannot be obtained by the conventional solid state reaction, and so on. In this paper, we review the progress of research on thin film fabrications of iron-based superconductors, especially the four categories: LnFeAs(O,F (Ln = Lanthanide, AEFe2As2 (AE = Alkaline-earth metal, FeCh (Ch = Chalcogen, and FeSe monolayer. Furthermore, we focus on two important topics in thin films of iron-based superconductors; one is the substrate material for thin film growth on the iron-based superconductors, and the other is the whole phase diagram in FeSe1-xTex which can be obtained only by using film-fabrication technique.
Application of high Tc superconductors as frequency selective surfaces: Experiment and theory

International Nuclear Information System (INIS)

Dawei Zhang; Yahya Rahmat-Samii; Fetterman, H.R.

1993-01-01

YBa 2 Cu 3 O 7-x and Tl 2 CaBa 2 Cu 2 O 8 high temperature superconducting thin films were utilized to fabricate frequency selective surfaces (FSS) at millimeter-wave frequencies (75--110 GHz). An analytical/numerical model was applied, using a Floquet expansion and the Method of Moments, to analyze bandstop superconducting frequency selective surfaces. Experimental results were compared with the model, and showed a good agreement with resonant frequency prediction with an accuracy of better than 1%. The use of the superconducting frequency selective surfaces as quasi-optical millimeter-wave bandpass filters was also demonstrated
Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

Science.gov (United States)

Wolak, M. A.; Tan, T.; Krick, A.; Johnson, E.; Hambe, M.; Chen, Ke; Xi, X. X.

2014-01-01

We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD). To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB2 films on these substrates showed uniformly good superconducting properties including Tc of 37-40 K, residual resistivity ratio of up to 14, and root-mean-square roughness Rq of 20-30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB2 by the HPCVD technique, an important step towards superconducting rf cavities with MgB2 coating.
Di- and tri-carboxylic-acid-based etches for processing high temperature superconducting thin films and related materials

International Nuclear Information System (INIS)

Ginley, D.S.; Barr, L.; Ashby, C.I.H.; Plut, T.A.; Urea, D.; Siegal, M.P.; Martens, J.S.; Johansson, M.E.

1994-01-01

The development of passive and active electronics from high-temperature superconducting thin films depends on the development of process technology capable of producing appropriate feature sizes without degrading the key superconducting properties. We present a new class of chelating etches based on di- and tri-carboxylic acids that are compatible with positive photoresists and can produce sub-micron feature sizes while typically producing increases the microwave surface resistance at 94 GHz by less than 10%. This simple etching process works well for both the Y--Ba--Cu--O and Tl--Ba--Ca--Cu--O systems. In addition, we demonstrate that the use of chelating etches with an activator such as HF allows the etching of related oxides such as LaAlO 3 , which is a key substrate material, and Pb(Zr 0.53 Ti 0.47 )O 3 (PZT) which is a key ferroelectric material for HTS and other applications such as nonvolatile memories
Spin-fluctuation mechanism of high-Tc superconductivity and order-parameter symmetry

International Nuclear Information System (INIS)

Izyumov, Yurii A

1999-01-01

The notion that electrons in high-T c cuprates pair via antiferromagnetic spin fluctuations is discussed and the symmetry of the superconducting order parameter is analyzed. Three approaches to the problem, one phenomenological (with an experimental dynamic magnetic susceptibility) and two microscopic (involving, respectively, the Hubbard model and the tJ-model) are considered and it is shown that in each case strong-coupling theory leads to a d-wave order parameter with zeros at the Fermi surface. The review then proceeds to consider experimental techniques in which the d-symmetry of the order parameter may manifest itself. These include low-temperature thermodynamic measurements, measurements of the penetration depth and the upper critical field, Josephson junction experiments to obtain the phase of the superconducting order parameter, and various spectroscopic methods. The experimental data suggest that the order parameter in cuprates is d x 2 -y 2 -wave. Ginzburg-Landau theory for a superconductor with a d-wave order parameter is outlined and both an isolated vortex and a vortex lattice are investigated. Finally, some theoretical aspects of the effects of nonmagnetic impurities on a d-wave superconductor are considered. (reviews of topical problems)
High-temperature superconductivity

International Nuclear Information System (INIS)

Ginzburg, V.L.

1987-07-01

After a short account of the history of experimental studies on superconductivity, the microscopic theory of superconductivity, the calculation of the control temperature and its possible maximum value are presented. An explanation of the mechanism of superconductivity in recently discovered superconducting metal oxide ceramics and the perspectives for the realization of new high-temperature superconducting materials are discussed. 56 refs, 2 figs, 3 tabs
Superconductivity and ceramic superconductors II; Proceedings of the Symposium, Orlando, FL, Nov. 12-15, 1990. Ceramic transactions. Vol. 18

International Nuclear Information System (INIS)

Nair, K.M.; Balachandran, U.; Chiang, Y.-M.; Bhalla, A.S.

1991-01-01

The present symposium on superconductivity and ceramic superconductors discusses fundamentals and general principles, powder processing and properties, fabrication and properties, and device reliability and applications. Attention is given to phase formation in the Tl-Ca-Ba-Cu-O system, comparative defect studies in La2CuO4 and La2NiO4, solid solution and defect behavior in high Tc oxides, oxygen ion transport and disorder in cuprates, and Sr-free Bi-Ln-Ca-Cu-O superconductors. Topics addressed include the preparation of superconductor Y-Ba-Cu-O powder by single-step calcining in air, low-temperature synthesis of YBa2Cu3O(7-x), synthesis of high-phase purity ceramic oxide superconductors by the xerogel method, and the preparation and characterization of the BYa2Cu4O8 superconductor. Also discussed are optical studies of humidity-based corrosion effects on thin film and bulk ceramic YBa2Cu3O(7-delta), thermomechanical processing of YBa2Cu3O(x)/Ag sheathed wires, and the expansion of high-Tc superconducting ceramics
Development of Strontium Titanate Thin films on Technical Substrates for Superconducting Coated Conductors

DEFF Research Database (Denmark)

Pallewatta, Pallewatta G A P; Yue, Zhao; Grivel, Jean-Claude

2012-01-01

SrTiO3 is a widely studied perovskite material due to its advantages as a template for high temperature superconducting tapes. Heteroepitaxial SrTiO3 thin films were deposited on Ni/W tapes using dip-coating in a precursor solution followed by drying and annealing under reducing conditions. Nearl...
Comparison of film sensitivity for sup(99m)Tc gamma-rays

International Nuclear Information System (INIS)

Kojima, Kazuhiko; Katayama, Masaharu; Hisada, Kinichi.

1975-01-01

Recently a new method of γ-ray imaging by holography has been studied at several nuclear medical laboratories. The holography is of a very simple. An axis Fresnel zone plate made of lead (2 mm thickness) is placed between the γ-ray source and a detector, and its shadow is recorded as a hologram. The hologram obtained is illuminated by parallel beams of He-Ne laser (6328 A), and an image of the radioisotope distribution in the object is reconstructed by diffraction. The better the resolution of the shadow hologram, the better are the reconstructed images obtained. For this reason the detector for recording the γ-ray hologram must be selected carefully. Three kinds of medical X-ray film were used as detectors for holograms to compare film sensitivity. Generally these medical X-ray films have poor sensitivity to γ-rays of sup(99m)Tc. In order to intensify the film sensitivity for γ-rays of sup(99m)Tc, combinations of six kinds of intensifying screens were studied. Good film sensitivity was obtained by RP (Kodak Co.) film combined with a KZ-S fluorescent intensifying screen. The fluorescent screen was better than fluorometallic screens with similar properties. Using this film-screen combination, shadow holograms could be recorded for 2-3 minutes and images could be optically reconstructed. (auth.)
Study on magnetic separation system using high Tc superconducting bulk magnets for water purification technique

International Nuclear Information System (INIS)

Oka, T; Kanayama, H; Tanaka, K; Fukui, S; Ogawa, J; Sato, T; Ooizumi, M; Yamaguchi, M; Yokoyama, K; Noto, K

2009-01-01

The application of superconducting bulk magnets to the magnetic separation techniques has been investigated for the Mn-bearing waste water drained from the university laboratories. The research has been conducted in comparison with the electromagnets, and the cryo-cooled superconducting solenoid magnet. The separation ratios of ferrite precipitates including Mn element in the waste slurry were estimated by means of the high gradient magnetic separation method with ferromagnetic iron filters in the water channel and open gradient magnetic separation without them. As the magnetic force acting on the particles is given by the product of a magnetization of particles and a gradient of magnetic field, and a superconducting bulk magnet shows a sharp gradient of the magnetic field on the surface, the performances of the bulk magnet system were almost equivalent to those of the superconducting solenoid magnet with wide bore with respect to the magnetic separation ratios. The separation ratios for Mn have reached over 80 % for HGMS and 10 % for OGMS under the flow rates less than 3 liter/min.
Bi--Sr--Ca--Cu--O superconducting films fabricated using metal alkoxides

International Nuclear Information System (INIS)

Katayama, S.; Sekine, M.

1991-01-01

Superconducting films in the Bi--Sr--Ca--Cu--O systems were made using metal alkoxides. To prepare a dip-coating solution using a mixed alkoxide solution, insoluble Cu and Bi alkoxides were dissolved by modification with 2-dimethylaminoethanol and formation of a double alkoxide, respectively. Formation of the double alkoxides of Bi with Ca or Sr was confirmed using FT-IR and 1 H-NMR. Bi--Sr--Ca--Cu--O films on yttria-stabilized ZrO 2 and single crystal MgO(100) substrates were made using this solution. The films were closely oriented along the c-axis perpendicular to the substrate. The film on MgO(100) fired at 850 degree C for 48 h showed two resistance drops around 115 and 85 K, corresponding to the high-T c and low-T c phases, respectively, and zero resistance at 72 K
Chemical casting of high-Tc superconducting BiSCCO

International Nuclear Information System (INIS)

Toth, L.E.; Das, B.N.; Rayne, R.J.; Bender, B.A.; Lechter, W.L.; Hoff, H.A.; Osofsky, M.S.; Soulen, R.J. Jr.

1989-01-01

BiSCCO has been successfully cast into a number of useful shapes. This casting process differs significantly from traditional casting in that the process includes a change in the oxygen content of the melt. A heat treatment is required to restore the original chemistry, properly form the BiSCCO crystal structure and develop the superconducting properties. This paper emphasizes the microstructures of as-cast and heat treated BiSCCO. Casting causes considerable grain alignment of the BiSCCO platelets. The platelets align preferentially along the thermal gradients which exist during the solidification process
Influence of annealing atmosphere on structural and superconducting properties of MgB{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Gregor, M., E-mail: gregor@fmph.uniba.sk; Plecenik, T.; Sobota, R.; Brndiarova, J.; Roch, T.; Satrapinskyy, L.; Kus, P.; Plecenik, A.

2014-09-01

Highlights: • Superconducting MgB{sub 2} thin film were deposited by co-deposition using the thermal and e-beam evaporation. • Ex situ annealing process was done using various atmospheres. • Influence of annealing atmosphere and temperature on superconducting and structural properties were studied. • Possible mechanisms of the formation and crystallization of MgB{sub 2} thin film are discussed. - Abstract: Influence of an ex situ annealing temperature and atmosphere on chemical composition and structural and superconducting properties of MgB{sub 2} thin films deposited by vacuum evaporation has been investigated. The annealing has been done in Ar, N{sub 2} and Ar + 5%H{sub 2} atmospheres at pressure of 700 Pa and temperature varying from 700 to 800 °C. It has been shown that annealing in Ar and N{sub 2} atmosphere at 700–800 °C produces relatively thick MgO layer on the surface of the films, while creation of such layer is highly reduced if the annealing is done in reducing Ar + 5%H{sub 2} atmosphere. The XPS and XRD results suggest that the MgO layer prevents out-diffusion of Mg from the film during the annealing, what assures better stoichiometry of the films as well as creation of larger MgB{sub 2} grains. The films with the highest amount of MgO on the surface, annealed in nitrogen atmosphere, thus paradoxically exhibited the highest critical temperature of T{sub c0} = 34.8 K with very sharp transition width of 0.1 K.
High-temperature superconductivity from fine-tuning of Fermi-surface singularities in iron oxypnictides

Science.gov (United States)

Charnukha, A.; Evtushinsky, D. V.; Matt, C. E.; Xu, N.; Shi, M.; Büchner, B.; Zhigadlo, N. D.; Batlogg, B.; Borisenko, S. V.

2015-12-01

In the family of the iron-based superconductors, the REFeAsO-type compounds (with RE being a rare-earth metal) exhibit the highest bulk superconducting transition temperatures (Tc) up to 55 K and thus hold the key to the elusive pairing mechanism. Recently, it has been demonstrated that the intrinsic electronic structure of SmFe0.92Co0.08AsO (Tc = 18 K) is highly nontrivial and consists of multiple band-edge singularities in close proximity to the Fermi level. However, it remains unclear whether these singularities are generic to the REFeAsO-type materials and if so, whether their exact topology is responsible for the aforementioned record Tc. In this work, we use angle-resolved photoemission spectroscopy (ARPES) to investigate the inherent electronic structure of the NdFeAsO0.6F0.4 compound with a twice higher Tc = 38 K. We find a similarly singular Fermi surface and further demonstrate that the dramatic enhancement of superconductivity in this compound correlates closely with the fine-tuning of one of the band-edge singularities to within a fraction of the superconducting energy gap Δ below the Fermi level. Our results provide compelling evidence that the band-structure singularities near the Fermi level in the iron-based superconductors must be explicitly accounted for in any attempt to understand the mechanism of superconducting pairing in these materials.

Thermal coupling effect on the vortex dynamics of superconducting thin films: time-dependent Ginzburg–Landau simulations

Science.gov (United States)

Jing, Ze; Yong, Huadong; Zhou, Youhe

2018-05-01

In this paper, vortex dynamics of superconducting thin films are numerically investigated by the generalized time-dependent Ginzburg–Landau (TDGL) theory. Interactions between vortex motion and the motion induced energy dissipation is considered by solving the coupled TDGL equation and the heat diffusion equation. It is found that thermal coupling has significant effects on the vortex dynamics of superconducting thin films. Branching in the vortex penetration path originates from the coupling between vortex motion and the motion induced energy dissipation. In addition, the environment temperature, the magnetic field ramp rate and the geometry of the superconducting film also greatly influence the vortex dynamic behaviors. Our results provide new insights into the dynamics of superconducting vortices, and give a mesoscopic understanding on the channeling and branching of vortex penetration paths during flux avalanches.
Assessment of potential advantages of high Tc-superconductors for technical application of superconductivity

International Nuclear Information System (INIS)

Schauer, F.; Juengst, K.P.; Komarek, P.; Maurer, W.

1987-09-01

A first assessment of the technical and economical consequences of liquid nitrogen cooling of new superconductors is given. For the investigation the applications of superconductivity are classified in two categories: First, systems where superconductors are practically indispensable for achieving the system's objectives; second, superconductor applications in competition with highly developed conventional technologies. Further development of those superconducting systems in the first category for which the cost of cryogenic equipment is a smaller fraction of the total system cost (e.g. fusion reactor or MHD generator) will hardly be affected. However, for systems like particle accelerators, research magnets, and NMR spectroscopy and imaging systems, the cryogenic equipment expenditures are significant and LN 2 cooling leads here to a reduction of investment and operating costs, to simplified handling and maintenance, to better reliability and availability, and will thereby improve the acceptance and further spread of these systems. In the second category each application of superconductivity has to be compared with its conventional counterpart, separately. Here, electonic components, power switches, resistive current limiters, and especially the power transmission cables are those applications which look most promising. For magnet applications the main advantageous arguments are less the cost saving aspect but more the higher reliability, simplicity, N 2 -availability, and ease of handling. (orig.) [de
Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

International Nuclear Information System (INIS)

Bedekar, M.M.

1992-01-01

The discovery of a new class of copper oxide superconductors has led to the development of three major systems that exhibit superconducting properties. The Bi-Sr-Ca-Cu-O superconductors offer intrinsic advantages due to the high T c , chemical inertness and tolerance for a range of compositions. However, thin film research on these materials has progressed more slowly than the other cuprate systems. This dissertation examines the film growth, by laser ablation, of the Bi-Sr-Ca-Cu-O superconductors and the effect of the deposition parameters such as the laser target interaction, substrate temperature, target to substrate distance, deposition and cooling pressure, target type and processing and the substrate type. CO 2 laser ablation was shown to give rise to a non-stoichiometric material transfer due to the low fluences and long pulse lengths. In situ superconducting thin films with T c(0) 's of 76 K could be deposited using the KrF laser at substrate temperatures of 5 degrees C to 20 degrees C below phases. Lower temperatures gave rise to a mixture of 2201 and glassy phases. An increase in the target to substrate distance led to a deterioration of the electrical and structural properties of the films due to a decrease in the energy for film formation. A maximum in T c(0) was observed at 450 mtorr as the deposition pressure was varied between 200 to 700 mtorr. Optimum oxygen incorporation could be achieved by cooling the films in high oxygen pressures and the best films were obtained with 700 torr cooling pressure. The oxygen deficiency of the hot pressed targets led to inferior properties compared to the conventionally sintered targets. The microwave surface resistance of the films measured at 35 GHz showed an onset at 80 K and dropped below that of copper at 30 K. The study of the laser ablation process in this system revealed the presence of a stoichiometric forward directed component and a diffuse evaporation component
The NMR probe of high-Tc materials and correlated electron systems

CERN Document Server

Walstedt, Russell E

2018-01-01

This new edition updates readers in three areas of NMR studies, namely, recent developments in high-Tc materials, heavy fermion systems and actinide oxides are presented. The NMR probe has yielded a vast array of data for solid state materials, corresponding to different compounds, ionic sites, and nuclear species, as well as to a wide variety of experimental conditions. The last two parts of the book are completely new in this edition, while the first part has seen major updates. This edition features the latest developments for high-Tc materials, especially the advances in the area of pseudogap studies are reviewed. An in depth overview of heavy fermion systems is presented in the second part, notably Kondo lattices, quantum critical points and unconventional superconductivity are areas of intense research recently and are covered extensively. Finally, valuable information from NMR studies with actinide oxides will be provided. Ongoing analysis and discussion of NMR data have resulted in a wealth o...
Critical currents in multilayered superconducting films

International Nuclear Information System (INIS)

Raffy, Helene

1977-01-01

The superconducting critical currents Isub(c) were measured as a function of magnetic field H and temperature T, on multilayered films. These films consist of alternating layers of two different superconductors S 1 and S 2 being a weaker superconductor acting as a flux pinning barrier region. A strong anisotropy was observed between the two situations where the magnetic field H is applied parallel or perpendicular to the layers. In the case discussed, there is a peak effect in the curves Isub(c)H well defined at the highest temperatures, and disappearing at low temperatures. The anisotropy of the critical current at constant field presents a maximum at a temperature T* close to the critical temperature Tsub(c 2 ) of S 2 [fr
High-frequency applications of high-temperature superconductor thin films

Science.gov (United States)

Klein, N.

2002-10-01

High-temperature superconducting thin films offer unique properties which can be utilized for a variety of high-frequency device applications in many areas related to the strongly progressing market of information technology. One important property is an exceptionally low level of microwave absorption at temperatures attainable with low power cryocoolers. This unique property has initiated the development of various novel type of microwave devices and commercialized subsystems with special emphasis on application in advanced microwave communication systems. The second important achievement related to efforts in oxide thin and multilayer technology was the reproducible fabrication of low-noise Josephson junctions in high-temperature superconducting thin films. As a consequence of this achievement, several novel nonlinear high-frequency devices, most of them exploiting the unique features of the ac Josephson effect, have been developed and found to exhibit challenging properties to be utilized in basic metrology and Terahertz technology. On the longer timescale, the achievements in integrated high-temperature superconductor circuit technology may offer a strong potential for the development of digital devices with possible clock frequencies in the range of 100 GHz.
High-frequency applications of high-temperature superconductor thin films

International Nuclear Information System (INIS)

Klein, N.

2002-01-01

High-temperature superconducting thin films offer unique properties which can be utilized for a variety of high-frequency device applications in many areas related to the strongly progressing market of information technology. One important property is an exceptionally low level of microwave absorption at temperatures attainable with low power cryocoolers. This unique property has initiated the development of various novel type of microwave devices and commercialized subsystems with special emphasis on application in advanced microwave communication systems. The second important achievement related to efforts in oxide thin and multilayer technology was the reproducible fabrication of low-noise Josephson junctions in high-temperature superconducting thin films. As a consequence of this achievement, several novel nonlinear high-frequency devices, most of them exploiting the unique features of the ac Josephson effect, have been developed and found to exhibit challenging properties to be utilized in basic metrology and Terahertz technology. On the longer timescale, the achievements in integrated high-temperature superconductor circuit technology may offer a strong potential for the development of digital devices with possible clock frequencies in the range of 100 GHz. (author)
High Temperature Superconducting Films and Multilayers for Electronics

Science.gov (United States)

1994-04-19

Vol. 1292 (1990). U Chisholm, A. Gupta, S. Shinde and R.B. Bnidges. GAN. Connell and 1B. Boyce, Laibowitz, " Lanthanum Gallate Sub- "Properties of...aluminate or gallate ..._.........102 24 - 2:2:4:5 structure ........................ 115 IN - Interface reactions ............ 93 #M - MgO substrates...Draper with the measure- High-Tc Superconductors,’ Physica C. on Lanthanum Aluminate Subsbates." in ments of surface resistance; T.T. Vol. 153-155,19M8 pp
Levitation force and magnetization in bulk and thin film high Tc superconductors

International Nuclear Information System (INIS)

Riise, A.B

1998-04-01

The authors present high-resolution measurements of the repulsive vertical force and its associated stiffness between a Nd-B-Fe magnet and a YBa 2 Cu 3 O 7-δ superconductor in cylindrical geometry. The results are compared with theoretical predictions. The calculations are based on a model in which the superconductor is assumed to be either a sintered granular material or consisting of grains embedded in a nonactive matrix so that only intragranular currents are important. The critical state model is applied to each grain individually and closed form expressions for both vertical force F z and stiffness are obtained in a configuration with cylindrical symmetry. The model explains all features of the experimental results in a consistent way. A good quantitative agreement has been obtained using only three adjustable parameters. Several central aspects of the phenomenon of magnetic levitation with high-T c superconductors are presented. High-resolution measurements are made of the repulsive vertical force and its associated stiffness as well as the horizontal stabilizing force and the stiffness governing lateral vibrations. The results obtained at 77 K using a granular YBa 2 Cu 3 O 7-δ sample and Nd-Fe-B magnet in a rectangular levitation configuration are compared with theoretical predictions. The calculations, which are based on the critical state model with the assumption that it applies to the grins individually, give closed-form expressions for all the measured quantities. It is concluded that the present model explains all features of the observations in a consistent way. Using only three adjustable parameters a good agreement exists also at a quantitative level. Experimental studies and theoretical modelling of the levitation force on a permanent magnet placed above a superconducting thin film are offered. It is shown that measurements of the levitation force is a simple and precise method to determine the critical current density in thin films
Superconductivity under high pressure in the binary compound CaLi2

Science.gov (United States)

Debessai, M.; Matsuoka, T.; Hamlin, J. J.; Gangopadhyay, A. K.; Schilling, J. S.; Shimizu, K.; Ohishi, Y.

2008-12-01

Feng predicted for CaLi2 highly anomalous properties with possible superconductivity under very high pressures, including for the hcp polymorph a significant lattice bifurcation at pressures above 47 GPa. More recently, however, Feng suggested that for pressures exceeding 20 GPa CaLi2 may dissociate into elemental Ca and Li. Here we present for hcp CaLi2 measurements of the electrical resistivity and ac susceptibility to low temperatures under pressures as high as 81 GPa. Pressure-induced superconductivity is observed in the pressure range of 11-81 GPa, with Tc reaching values as high as 13 K. X-ray diffraction studies to 54 GPa at 150 K reveal that hcp CaLi2 undergoes a structural phase transition above 23 GPa to orthorhombic but does not dissociate into elemental Ca and Li. In the hcp phase a fit of the equation of state with the Murnaghan equation yields the bulk modulus Bo=15(2)GPa and dBo/dP=3.2(6) .
Characteristic study of high-Tc superconducting maglev under side-loading

International Nuclear Information System (INIS)

Wang Wei; Wang Jiasu; Liu Wei; Zheng Jun; Lin Qunxu; Pan Siting; Deng Zigang; Ma Guangtong; Wang Suyu

2009-01-01

In practical application of High-T c Superconducting (HTS) maglev, slant is an observable defect. It was caused by constantly one side on and off the vehicle by passengers. So far, this phenomenon has not been reported yet. In order to understand its influence on the stability of the HTS maglev, we experimentally studied the dynamic characteristic and slant effect of HTS maglev under center-load and side-load. It was found that load destabilizes the vehicle, and the side-load can obviously slant the vehicle body. In the end, the pre-load method was proposed to enhance the dynamic stability and suppress the slant, which proved to be considerably effective. These results are critical in practical running of HTS maglev
Depth profiling of superconducting thin films using rare gas ion sputtering with laser postionization

International Nuclear Information System (INIS)

Pallix, J.B.; Becker, C.H.; Missert, N.; Char, K.; Hammond, R.H.

1988-01-01

Surface analysis by laser ionization (SALI) has been used to examine a high-T/sub c/ superconducting thin film of nominal composition YBa 2 Cu 3 O 7 deposited on SrTiO 3 (100) by reactive magnetron sputtering. The main focus of this work was to probe the compositional uniformity and the impurity content throughout the 1800 A thick film having critical current densities of 1 to 2 x 10 6 A/cm 2 . SALI depth profiles show this film to be more uniform than thicker films (∼1 μm, prepared by electron beam codeposition) which were studied previously, yet the data show that some additional (non-superconducting) phases derived from Y, Ba, Cu, and O are still present. These additional phases are studied by monitoring the atomic and diatomic-oxide photoion profiles and also the depth profiles of various clusters (e.g. Y 2 O 2 + , Y 2 O 3 + , Y 3 O 4 + , Ba 2 O + , Ba 2 O 2 + , BaCu + , BaCuO + , YBaO 2 + , YSrO 2 + , etc.). A variety of impurities are observed to occur throughout the film including rather large concentrations of Sr. Hydroxides, F, Cl, and CO/sub x/ are evident particularly in the sample's near surface region (the top ∼100 A)
Determination of the electromagnetic field in a high-Tc linear superconducting resonator

International Nuclear Information System (INIS)

Trotel, A.; Sautrot, S.; Pyee, M.

1994-01-01

In this paper, the electromagnetic field configuration in a linear SHTC resonator is described. Two areas are considered: 1) the superconducting strip, 2) the dielectric around the strip. The calculation is based on the current density given by Bowers for an infinite superconducting line. The current density in the resonator is defined by these relations and the resonance conditions. (orig.)
Epitaxial YBa2Cu3O7 on biaxially textured (001) Ni: An approach to high critical current density superconducting tapes

International Nuclear Information System (INIS)

Norton, D.P.; Goyal, A.; Budai, J.D.

1997-01-01

In-plane aligned, c-axis oriented YBa 2 Cu 3 O 7 (YBCO) films with superconducting critical current densities, J c , as high as 700,000 amperes per square centimeter at 77 kelvin have been grown on thermo-mechanically, rolled-textured (001) Ni tapes using pulsed-laser deposition. Epitaxial growth of oxide buffer layers directly on biaxially textured Ni, formed by recrystallization of cold-rolled pure Ni, enables the growth of 1.5 micrometer-thick YBCO films with superconducting properties that are comparable to those observed for epitaxial films on single crystal oxide substrates. This result represents a viable approach for producing long-length superconducting tapes for high current, high field applications at 77 kelvin
Preparation of YBa2Cu3O7 films by low pressure MOCVD using liquid solution sources

International Nuclear Information System (INIS)

Weiss, F.; Froehlich, K.; Haase, R.; Labeau, M.; Selbmann, D.; Senateur, J.P.; Thomas, O.

1993-01-01

A hybrid low pressure MOCVD process is described for reproducible preparation of superconducting thin films of YBa 2 Cu 3 O 7 . The process uses a single solution source of Y, Ba, and Cu β-diketonates dissolved in suitable organic solvents. This liquid precursor is atomized using an ultrasonic aerosol generator and transported as small droplets (∼1μm) into a CVD reactor where solvent and precursor are first evaporated before deposition takes place at low pressure on heated substrates in a cold wall geometry. This process allows, with stable evaporation rates for all three precursors, to grow in-situ superconducting films with constant composition from film to film. Thin and thick films with high critical temperatures and critical currents have been obtained (Tc>80K, Jc>10 4 A/cm 2 at 77K in self field) which are highly c-axis oriented. Experimental details of this new process are described and the effects of different process parameters are studied in order to improve the quality of the deposited layers. (orig.)
Vortex variable range hopping in a conventional superconducting film

Science.gov (United States)

Percher, Ilana M.; Volotsenko, Irina; Frydman, Aviad; Shklovskii, Boris I.; Goldman, Allen M.

2017-12-01

The behavior of a disordered amorphous thin film of superconducting indium oxide has been studied as a function of temperature and magnetic field applied perpendicular to its plane. A superconductor-insulator transition has been observed, though the isotherms do not cross at a single point. The curves of resistance versus temperature on the putative superconducting side of this transition, where the resistance decreases with decreasing temperature, obey two-dimensional Mott variable-range hopping of vortices over wide ranges of temperature and resistance. To estimate the parameters of hopping, the film is modeled as a granular system and the hopping of vortices is treated in a manner analogous to hopping of charges. The reason the long-range interaction between vortices over the range of magnetic fields investigated does not lead to a stronger variation of resistance with temperature than that of two-dimensional Mott variable-range hopping remains unresolved.
Local imaging of magnetic flux in superconducting thin films

International Nuclear Information System (INIS)

Shapoval, Tetyana

2010-01-01

Local studies of magnetic flux line (vortex) distribution in superconducting thin films and their pinning by natural and artificial defects have been performed using low-temperature magnetic force microscopy (LT-MFM). Taken a 100 nm thin NbN film as an example, the depinning of vortices from natural defects under the influence of the force that the MFM tip exerts on the individual vortex was visualized and the local pinning force was estimated. The good agreement of these results with global transport measurements demonstrates that MFM is a powerful and reliable method to probe the local variation of the pinning landscape. Furthermore, it was demonstrated that the presence of an ordered array of 1-μm-sized ferromagnetic permalloy dots being in a magneticvortex state underneath the Nb film significantly influences the natural pinning landscape of the superconductor leading to commensurate pinning effects. This strong pinning exceeds the repulsive interaction between the superconducting vortices and allows vortex clusters to be located at each dot. Additionally, for industrially applicable YBa 2 Cu 3 O 7-δ thin films the main question discussed was the possibility of a direct correlation between vortices and artificial defects as well as vortex imaging on rough as-prepared thin films. Since the surface roughness (droplets, precipitates) causes a severe problem to the scanning MFM tip, a nanoscale wedge polishing technique that allows to overcome this problem was developed. Mounting the sample under a defined small angle results in a smooth surface and a monotonic thickness reduction of the film along the length of the sample. It provides a continuous insight from the film surface down to the substrate with surface sensitive scanning techniques. (orig.)
Routes to High-Temperature Superconductivity: A Lesson from FeSe/SrTiO3

Science.gov (United States)

Lee, Dung-Hai

2018-03-01

Raising the superconducting transition temperature to a point where applications are practical is one of the most important challenges in science. In this review, we aim at gaining insights on the Tc controlling factors for a particular high-temperature superconductor family - the FeSe-based superconductors. In particular, we discuss the mechanisms by which the Cooper pairing temperature is enhanced from ˜8 K in bulk FeSe to ˜80 K in the interface between an atomic layer of FeSe and SrTiO3. This includes the experimental hints and the theoretical simulation of the involved mechanisms. We end by applying these insights to suggest some possible high-temperature superconducting systems.
The Origin of Tc Enhancement in Heterostructure Cuprate Superconductors

Directory of Open Access Journals (Sweden)

Doron L. Bergman

2011-10-01

Full Text Available Recent experiments on heterostructures composed of two or more films of cuprate superconductors of different oxygen doping levels have shown a remarkable Tc enhancement (up to 50% relative to single compound films. We provide a simple explanation of the enhancement which arises naturally from a collection of experimental works. We show that the enhancement could be caused by a structural change in the lattice, namely an increase in the distance of the apical oxygen from the copper-oxygen plane. This increase modifies the effective off-site interaction in the plane which in turn enhances the d-wave superconductivity order parameter. To illustrate this point we study the extended Hubbard model using the fluctuation exchange approximation.
Growth of superconducting Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+//sub x/ films on alumina, silicon, and fused quartz

International Nuclear Information System (INIS)

Hung, L.S.; Agostinelli, J.A.; Paz-Pujalt, G.R.; Mir, J.M.

1988-01-01

Interactions between superconducting Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+//sub x/ films and substrates were investigated by ion backscattering, x-ray diffraction, and four-point probe resistivity measurements. During annealing at temperatures above- 800 /sup 0/C, Bi/sub 2/Sr/sub 2/CaCu/sub 2/ oxide films rapidly reacted with alumina, Si, Si covered with SiO/sub 2/, and quartz, resulting in catastrophic failure. Zr-based barrier layers were used to minimize film-substrate interactions. When a single ZrO/sub 2/ layer was interposed between the superconducting oxide film and the underlying substrate, the Bi/sub 2/Sr/sub 2/CaCu/sub 2/ oxide films showed a large-grained polycrystalline microstructure and exhibited the orthorhombic structure. Films on sapphire showed transitions to the superconducting state beginning near 100 K with zero resistance achieved at 70 K. Films on Si and thermally grown SiO/sub 2/ showed a similar drop in resistance around 95 K, whereas the transition was broad and the zero resistance state was not reached. For films on quartz, high thermal stress caused cracking of the superconducting oxide film. Best results were achieved using a barrier composed of a Zr-Si-O mixed layer underneath ZrO/sub 2/. In this case, the films grown on Si and quartz were uniform and showed the onset to superconductivity at 95 K, attaining zero resistance at 70 K

Robust zero resistance in a superconducting high-entropy alloy at pressures up to 190 GPa

Science.gov (United States)

Guo, Jing; Wang, Honghong; von Rohr, Fabian; Wang, Zhe; Cai, Shu; Zhou, Yazhou; Yang, Ke; Li, Aiguo; Jiang, Sheng; Wu, Qi; Cava, Robert J.; Sun, Liling

2017-12-01

We report the observation of extraordinarily robust zero-resistance superconductivity in the pressurized (TaNb)0.67(HfZrTi)0.33 high-entropy alloy--a material with a body-centered-cubic crystal structure made from five randomly distributed transition-metal elements. The transition to superconductivity (TC) increases from an initial temperature of 7.7 K at ambient pressure to 10 K at ˜60 GPa, and then slowly decreases to 9 K by 190.6 GPa, a pressure that falls within that of the outer core of the earth. We infer that the continuous existence of the zero-resistance superconductivity from 1 atm up to such a high pressure requires a special combination of electronic and mechanical characteristics. This high-entropy alloy superconductor thus may have a bright future for applications under extreme conditions, and also poses a challenge for understanding the underlying quantum physics.
Tunnelling investigation of the phonon spectrum of superconducting Be. Implications for an eventual enhancement of T(c)

International Nuclear Information System (INIS)

Leger, A.; Klein, J.; Cheveigne, S. de; Belin, M.; Defourneau, D.

1975-01-01

Beryllium is an exciting superconductor in that the theoretical upper limit for its T(c) is 140K. The possibility of increasing the critical temperature of the vapour quenched phase whose T(c) is already 9.5K is discussed. Tunnelling into films of this phase indicates that it is a weak coupling superconductor (lambda [fr
2+1 topological term, anyons and their possible application in high Tc superconductivity

International Nuclear Information System (INIS)

Zhu Chuanjie.

1990-01-01

I review pedagogically some aspects about the SO(3) non-linear σ-model and the topological Hopf term (or the abelian Chern-Simons term). I argue that the presence of the topological Chern-Simons term is irrelevant (for regular gauge field configurations). I also give a brief introduction to the ideal anyon gas approach to high T c superconductivity. (author). 18 refs
Microwave plasma CVD of oxide films relating to high Tc Bi-Sr-Ca-Cu-O superconductor

International Nuclear Information System (INIS)

Hashimoto, T.; Kosaka, T.; Yoshida, Y.; Yoshimoto, M.; Koinuma, H.

1989-01-01

Microwave plasma CVD was applied to the synthesis of Bi, Sr, Ca, and Cu oxide films at relatively low temperatures. Gas source materials used were Bi(C 6 H 5 ) 3 , Sr(PPM) 2 , Ca(PPM) 2 , and Cu(HFA) 2 , where PPM and HFA represent C 2 F 5 COCHCOC(CH 3 ) 3 and CF 3 COCHCOCF 3 , respectively. Films were deposited on MgO (100) substrate at temperatures between 200 C and 400 C under an atmosphere of 1000mTorr Ar-O 2 (50/100) mixture which was partially excited by plasma. From Bi(C 6 H 5 ) 3 , Bi 2 O 3 was formed at 200 C without containing carbon above the detection level by XPS analysis. From Cu(HFA) 2 , CuO was prepared at 400 C by increasing oxygen partial pressure to 0.1Torr. (At lower oxygen partial pressure, CuF 2 or amorphous films were deposited.) From Sr(PPM) 2 and Ca(PPM) 2 , SrF 2 and CaF 2 were obtained at 400 C. The attempt to fabricate superconducting films is also reported
Computer simulation of scattered ion and sputtered species effects in ion beam sputter-deposition of high temperature superconducting thin films

International Nuclear Information System (INIS)

Krauss, A.R.; Auciello, O.

1992-01-01

Ion beam sputter-deposition is a technique currently used by many groups to produce single and multicomponent thin films. This technique provides several advantages over other deposition methods, which include the capability for yielding higher film density, accurate stoichiometry control, and smooth surfaces. However, the relatively high kinetic energies associated with ion beam sputtering also lead to difficulties if the process is not properly controlled. Computer simulations have been performed to determine net deposition rates, as well as the secondary erosion, lattice damage, and gas implantation in the films, associated with primary ions scattered from elemental Y, Ba and Cu targets used to produce high temperature superconducting Y-Ba-Cu-O films. The simulations were performed using the TRIM code for different ion masses and kinetic energies, and different deposition geometries. Results are presented for primary beams of Ar + , Kr + and Xe + incident on Ba and Cu targets at 0 degrees and 45 degrees with respect to the surface normal, with the substrate positioned at 0 degrees and 45 degrees. The calculations indicate that the target composition, mass and kinetic energy of the primary beam, angle of incidence on the target, and position and orientation of the substrate affect the film damage and trapped primary beam gas by up to 5 orders of magnitude
Laser writing of superconducting patterns on YBa2Cu3Ox films

International Nuclear Information System (INIS)

Dye, R.C.; Muenchausen, R.E.; Nogar, N.S.; Mukherjee, A.; Brueck, S.R.J.

1990-01-01

A novel process for the direct laser writing of thin-film high T c patterns is demonstrated. The process consists of deposition of a high quality film (308 nm laser ablation from a YBa 2 Cu 3 O x target with a 750 degree C substrate temperature and a 150 mTorr O 2 ambient), annealing in an inert atmosphere (Ar at 400 degree C for 5--20 min) to reduce the oxygen content and depress or eliminate the superconducting transition temperature, and direct-write laser heating (1.06 μm at ∼0.5 kW/cm 2 for ∼5 min) in an oxygen atmosphere at ∼590 Torr to selectively regenerate the high T c material. rf eddy current and four-point resistivity probe results confirm this process for both SrTiO 3 and LaAlO 3 substrates. Scanning electron micrographs indicate that this is a very mild processing sequence with no observable changes in film morphology
Reduced thermal budget processing of Y--Ba--Cu--O high temperature superconducting thin films by metalorganic chemical vapor deposition

International Nuclear Information System (INIS)

Singh, R.; Sinha, S.; Hsu, N.J.; Ng, J.T.C.; Chou, P.; Thakur, R.P.S.; Narayan, J.

1991-01-01

Metalorganic chemical vapor deposition (MOCVD) has the potential of emerging as a viable technique to fabricate ribbons, tapes, coated wires, and the deposition of films of high temperature superconductors, and related materials. As a reduced thermal budget processing technique, rapid isothermal processing (RIP) based on incoherent radiation as the source of energy can be usefully coupled to conventional MOCVD. In this paper we report on the deposition and characterization of high quality superconducting thin films of Y--Ba--Cu--O (YBCO) on MgO and SrTiO 3 substrates by RIP assisted MOCVD. By using a mixture of N 2 O and O 2 as the oxygen source films deposited initially at 600 degree C for 1 min and then at 740 degree C for 30 min are primarily c-axis oriented and with zero resistance being observed at 84 and 89 K for MgO and SrTiO 3 substrates, respectively. The zero magnetic field current densities at 77 K for MgO and SrTiO 3 substrates are 1.2x10 6 and 1.5x10 6 A/cm 2 , respectively. It is envisaged that high energy photons from the incoherent light source and the use of a mixture of N 2 O and O 2 as the oxygen source, assist chemical reactions and lower overall thermal budget for processing of these films
Nano-engineered pinning centres in YBCO superconducting films

Energy Technology Data Exchange (ETDEWEB)

Crisan, A., E-mail: adrian.crisan@infim.ro [National Institute for Materials Physics Bucharest, 105 bis Atomistilor Str., 077125 Magurele (Romania); School of Metallurgy and Materials, University of Birmingham, Edgbaston, B15 2TT Birmingham (United Kingdom); Dang, V.S. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, B15 2TT Birmingham (United Kingdom); Nano and Energy Center, VNU Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Mikheenko, P. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, B15 2TT Birmingham (United Kingdom); Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo (Norway)

2017-02-15

Highlights: • Power applications of YBCO films/coated conductors in technological relevant magnetic fields requires nano-engineered pinning centre. • Three approaches have been proposed: substrate decoration, quasi-multilayers, and targets with secondary phase nano-inclusions. • Combination of all three approaches greatly increased critical current in YBCO films. • Bulk pinning force, pinning potential, and critical current density are estimated and discussed in relation with the type and strength of pinning centres related to the defects evidenced by Transmission Electron Microscopy. - Abstract: For practical applications of superconducting materials in applied magnetic fields, artificial pinning centres in addition to natural ones are required to oppose the Lorentz force. These pinning centres are actually various types of defects in the superconductor matrix. The pinning centres can be categorised on their dimension (volume, surface or point) and on their character (normal cores or Δκ cores). Different samples have been produced by Pulsed Laser Deposition, with various thicknesses, temperatures and nanostructured additions to the superconducting matrix. They have been characterized by SQUID Magnetic Properties Measurement System and Physical Properties Measurement System, as well as by Transmission Electron Microscopy (TEM). Correlations between pinning architecture, TEM images, and critical currents at various fields and field orientations will be shown for a large number of YBa{sub 2}Cu{sub 3}O{sub x} films with various types and architectures of artificial pinning centres.
Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

Directory of Open Access Journals (Sweden)

M. A. Wolak

2014-01-01

Full Text Available We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD. To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB_{2} films on these substrates showed uniformly good superconducting properties including T_{c} of 37–40 K, residual resistivity ratio of up to 14, and root-mean-square roughness R_{q} of 20–30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB_{2} by the HPCVD technique, an important step towards superconducting rf cavities with MgB_{2} coating.
Superconducting niobium nitride films deposited by unbalanced magnetron sputtering

Energy Technology Data Exchange (ETDEWEB)

Olaya, J.J. [Departamento de Ingenieria Mecanica y Mecatronica, Universidad Nacional de Colombia, Ciudad Universitaria, Carrera 30 Numero 45-03, Bogota (Colombia); Huerta, L. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, CU Coyoacan, Mexico D.F. 04510 (Mexico); Rodil, S.E. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, CU Coyoacan, Mexico D.F. 04510 (Mexico)], E-mail: ser42@iim.unam.mx; Escamilla, R. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, CU Coyoacan, Mexico D.F. 04510 (Mexico)

2008-10-01

Niobium nitride (NbN) thin films were deposited under different configurations of the magnetic field using a magnetron sputtering system. The magnetic field configuration varied from balanced to unbalanced leading to different growth conditions and film properties. The aim of the paper was to identify correlations between deposition conditions, film properties and the electrical properties, specially the superconductive critical temperature (T{sub C}). The results suggested that there is a critical deposition condition, having an optimum ion-atom arrival ratio that promotes a well ordered and textured nanocrystalline structure (cubic phase) with the minimum residual stress and only under this condition a high critical temperature (16K) was obtained. Lower T{sub C} values around 12K were obtained for the NbN samples having a lower degree of structural perfection and texture, and a larger fraction of intergranular voids. On the other hand, analysis of valence-band spectra showed that the contribution of the Nb 4d states remained essentially constant while the higher T{sub C} was correlated to a higher contribution of the N 2p states.
Superconducting niobium nitride films deposited by unbalanced magnetron sputtering

International Nuclear Information System (INIS)

Olaya, J.J.; Huerta, L.; Rodil, S.E.; Escamilla, R.

2008-01-01

Niobium nitride (NbN) thin films were deposited under different configurations of the magnetic field using a magnetron sputtering system. The magnetic field configuration varied from balanced to unbalanced leading to different growth conditions and film properties. The aim of the paper was to identify correlations between deposition conditions, film properties and the electrical properties, specially the superconductive critical temperature (T C ). The results suggested that there is a critical deposition condition, having an optimum ion-atom arrival ratio that promotes a well ordered and textured nanocrystalline structure (cubic phase) with the minimum residual stress and only under this condition a high critical temperature (16K) was obtained. Lower T C values around 12K were obtained for the NbN samples having a lower degree of structural perfection and texture, and a larger fraction of intergranular voids. On the other hand, analysis of valence-band spectra showed that the contribution of the Nb 4d states remained essentially constant while the higher T C was correlated to a higher contribution of the N 2p states
Lighting up superconducting stripes

Science.gov (United States)

Ergeçen, Emre; Gedik, Nuh

2018-02-01

Cuprate superconductors display a plethora of complex phases as a function of temperature and carrier concentration, the understanding of which could provide clues into the mechanism of superconductivity. For example, when about one-eighth of the conduction electrons are removed from the copper oxygen planes in cuprates such as La2‑xBaxCuO4 (LBCO), the doped holes (missing electrons) organize into one-dimensional stripes (1). The bulk superconducting transition temperature (Tc) is greatly reduced, and just above Tc, electrical transport perpendicular to the planes (along the c axis) becomes resistive, but parallel to the copper oxygen planes, resistivity remains zero for a range of temperatures (2). It was proposed a decade ago (3) that this anisotropic behavior is caused by pair density waves (PDWs); superconducting Cooper pairs exist along the stripes within the planes but cannot tunnel to the adjacent layers. On page 575 of this issue, Rajasekaran et al. (4) now report detection of this state in LBCO using nonlinear reflection of high-intensity terahertz (THz) light.
Local imaging of magnetic flux in superconducting thin films

Energy Technology Data Exchange (ETDEWEB)

Shapoval, Tetyana

2010-01-26

Local studies of magnetic flux line (vortex) distribution in superconducting thin films and their pinning by natural and artificial defects have been performed using low-temperature magnetic force microscopy (LT-MFM). Taken a 100 nm thin NbN film as an example, the depinning of vortices from natural defects under the influence of the force that the MFM tip exerts on the individual vortex was visualized and the local pinning force was estimated. The good agreement of these results with global transport measurements demonstrates that MFM is a powerful and reliable method to probe the local variation of the pinning landscape. Furthermore, it was demonstrated that the presence of an ordered array of 1-{mu}m-sized ferromagnetic permalloy dots being in a magneticvortex state underneath the Nb film significantly influences the natural pinning landscape of the superconductor leading to commensurate pinning effects. This strong pinning exceeds the repulsive interaction between the superconducting vortices and allows vortex clusters to be located at each dot. Additionally, for industrially applicable YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films the main question discussed was the possibility of a direct correlation between vortices and artificial defects as well as vortex imaging on rough as-prepared thin films. Since the surface roughness (droplets, precipitates) causes a severe problem to the scanning MFM tip, a nanoscale wedge polishing technique that allows to overcome this problem was developed. Mounting the sample under a defined small angle results in a smooth surface and a monotonic thickness reduction of the film along the length of the sample. It provides a continuous insight from the film surface down to the substrate with surface sensitive scanning techniques. (orig.)
James C. McGroddy Prize Talk: Superconductivity in alkali-metal doped Carbon-60

Science.gov (United States)

Hebard, Arthur

2008-03-01

Carbon sixty (C60), which was first identified in 1985 in laser desorption experiments, is unquestionably an arrestingly beautiful molecule. The high symmetry of the 12 pentagonal and 20 hexagonal faces symmetrically arrayed in a soccer-ball like structure invites special attention and continues to stimulate animated speculation. The availability in 1990 of macroscopic amounts of purified C60 derived from carbon-arc produced soot allowed the growth and characterization of both bulk and thin-film samples. Crystalline C60 is a molecular solid held together by weak van der Waals forces. The fcc structure has a 74% packing fraction thus allowing ample opportunity (26% available volume) for the intercalation of foreign atoms into the interstitial spaces of the three dimensional host. This opportunity catalyzed much of the collaborative work amongst chemists, physicists and materials scientists at Bell Laboratories, and resulted in the discovery of superconductivity in alkali-metal doped C60 with transition temperatures (Tc) in the mid-30-kelvin range. In this talk I will review how the successes of this initial team effort stimulated a worldwide collaboration between experimentalists and theorists to understand the promise and potential of an entirely new class of superconductors containing only two elements, carbon and an intercalated alkali metal. Although the cuprates still hold the record for the highest Tc, there are still open scientific questions about the mechanism that gives rise to such unexpectedly high Tc's in the non-oxide carbon-based superconductors. The doped fullerenes have unusual attributes (e.g., narrow electronic bands, high disorder, anomalous energy scales, and a tantalizing proximity to a metal-insulator Mott transition), which challenge conventional thinking and at the same time provide useful insights into new directions for finding even higher Tc materials. The final chapter of the `soot to superconductivity' story has yet to be written.
Mixed pinning landscape in nanoparticle-introduced YGdBa2Cu3Oy films grown by metal organic deposition

Science.gov (United States)

Miura, M.; Maiorov, B.; Baily, S. A.; Haberkorn, N.; Willis, J. O.; Marken, K.; Izumi, T.; Shiohara, Y.; Civale, L.

2011-05-01

We study the field (H) and temperature (T) dependence of the critical current density (Jc) and irreversibility field (Hirr) at different field orientations in Y0.77Gd0.23Ba2Cu3Oy with randomly distributed BaZrO3 nanoparticles (YGdBCO+BZO) and YBa2Cu3Oy (YBCO) films. Both MOD films have large RE2Cu2O5 (225) nanoparticles (˜80 nm in diameter) and a high density of twin boundaries (TB). In addition, YGdBCO+BZO films have a high density of BZO nanoparticles (˜25 nm in diameter). At high temperatures (T > 40 K), the superconducting properties, such as Jc, Hirr, and flux creep rates, are greatly affected by the BZO nanoparticles, while at low temperatures the superconducting properties of both the YBCO and YGdBCO+BZO films show similar field and temperature dependencies. In particular, while the Jc of YBCO films follow a power-law dependence (∝H-α) at all measured T, this dependence is only followed at low T for YGdBCO+BZO films. As a function of T, the YGdBCO+BZO film shows Jc(T,0.01T)~[1-(T/Tc)2]n with n ˜ 1.24 ± 0.05, which points to “δTc pinning.” We analyze the role of different types of defects in the different temperature regimes and find that the strong pinning of the BZO nanoparticles yields a higher Hirr and improved Jc along the c axis and at intermediate orientations at high T. The mixed pinning landscapes due to the presence of disorder of various dimensionalities have an important role in the improvement of in-field properties.
Superconducting critical temperature under pressure

Science.gov (United States)

González-Pedreros, G. I.; Baquero, R.

2018-05-01

The present record on the critical temperature of a superconductor is held by sulfur hydride (approx. 200 K) under very high pressure (approx. 56 GPa.). As a consequence, the dependence of the superconducting critical temperature on pressure became a subject of great interest and a high number of papers on of different aspects of this subject have been published in the scientific literature since. In this paper, we calculate the superconducting critical temperature as a function of pressure, Tc(P), by a simple method. Our method is based on the functional derivative of the critical temperature with the Eliashberg function, δTc(P)/δα2F(ω). We obtain the needed coulomb electron-electron repulsion parameter, μ*(P) at each pressure in a consistent way by fitting it to the corresponding Tc using the linearized Migdal-Eliashberg equation. This method requires as input the knowledge of Tc at the starting pressure only. It applies to superconductors for which the Migdal-Eliashberg equations hold. We study Al and β - Sn two weak-coupling low-Tc superconductors and Nb, the strong coupling element with the highest critical temperature. For Al, our results for Tc(P) show an excellent agreement with the calculations of Profeta et al. which are known to agree well with experiment. For β - Sn and Nb, we found a good agreement with the experimental measurements reported in several works. This method has also been applied successfully to PdH elsewhere. Our method is simple, computationally light and gives very accurate results.
Development of microstructure and superconductivity of silver-clad Bi(2223) composite tapes in the process of heat treatment

International Nuclear Information System (INIS)

Guo, Y.C.; Liu, H.K.; Dou, S.X.

1994-01-01

A systematic study on the development of phase composition, microstructure and superconducting properties (critical temperature Tc and critical current density J c ) in silver-clad (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10 composite tapes during the process of heat treatment has been conducted using X-ray diffraction, scanning electron microscopy and electrical measurements. The correlation between the tape's high Tc phase purity, microstructure and superconducting properties at different heat treatment stages has been carefully analysed and explained. The results indicate that pure high Tc phase, high degree of grain alignment, high mass density and good connection between grains are all essential for superconducting tapes to carry a large current. With the optimized process parameters, a critical current density J c up to 32665 A cm -2 (corresponding critical current, 42.3 A) at 77 K and self-magnetic field for silver-clad (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10 superconducting composite tapes has been achieved. (orig.)
MgB2 thick films on three-dimensional structures fabricated by HPCVD

Science.gov (United States)

Guo, Zhengshan; Cai, Xingwei; Liao, Xuebin; Chen, Yiling; Yang, Can; Niu, Ruirui; Luo, Wenhao; Huang, Zigeng; Feng, Qingrong; Gan, Zizhao

2018-06-01

Magnetic shielding has been a key factor in the measurement of ultra-weak magnetic fields, especially for shielding from low frequency electromagnetic noise. With the recent development of superconducting quantum interference devices, superconducting magnetic shielding has become an important area of research. MgB2 has shown great potential in magnetic shielding for its remarkable superconducting properties, the feasibility of its use in this capacity having been demonstrated by MgB2 bulk samples. However, the potential for application of such bulk samples is limited. In this work, we have investigated the possibility of the fabrication of MgB2 films on three-dimensional (3D) structures using a hybrid physical‑chemical vapor deposition system. MgB2 films 10 μm thick have been fabricated on the outer surface of a polycrystalline Al2O3 cylinder. The deposited film showed a transition temperature (TC) of 39 K and J C of 5.1 × 105 A · cm‑2, which are comparable to those of planar MgB2 films. This work shows the feasibility of depositing MgB2 films onto a 3D structure, and sheds light on the potential use of MgB2 films in superconducting magnetic shielding.
Macroscopic Magnetic Coupling Effect: The Physical Origination of a High-Temperature Superconducting Flux Pump

Science.gov (United States)

Wang, Wei; Coombs, Tim

2018-04-01

We have uncovered at the macroscopic scale a magnetic coupling phenomenon in a superconducting YBa2Cu3O7 -δ (YBCO) film, which physically explains the mechanism of the high-temperature superconducting flux pump. The coupling occurs between the applied magnetic poles and clusters of vortices induced in the YBCO film, with each cluster containing millions of vortices. The coupling energy is verified to originate from the inhomogeneous field of the magnetic poles, which reshapes the vortex distribution, aggregates millions of vortices into a single cluster, and accordingly moves with the poles. A contrast study is designed to verify that, to provide the effective coupling energy, the applied wavelength must be short while the field amplitude must be strong, i.e., local-field inhomogeneity is the crucial factor. This finding broadens our understanding of the collective vortex behavior in an applied magnetic field with strong local inhomogeneity. Moreover, this phenomenon largely increases the controlled vortex flow rate by several orders of magnitude compared with existing methods, providing motivation for and physical support to a new branch of wireless superconducting dc power sources, i.e., the high-temperature superconducting flux pump.
High magnetic field properties of Fe-pnictide thin films

Energy Technology Data Exchange (ETDEWEB)

Kurth, Fritz

2015-11-20

The recent discovery of high-temperature superconductivity in Fe-based materials triggered worldwide efforts to investigate their fundamental properties. Despite a lot of similarities to cuprates and MgB{sub 2}, important differences like near isotropic behaviour in contrast to cuprates and the peculiar pairing symmetry of the order parameter (OP) have been reported. The OP symmetry of Fe-based superconductors (FBS) was theoretically predicted to be of so-called s± state prior to various experimental works. Still, most of the experimental results favour the s± scenario; however, definitive evidence has not yet been reported. Although no clear understanding of the superconducting mechanisms yet exists, potential applications such as high-field magnets and Josephson devices have been explored. Indeed, a lot of reports about FBS tapes, wires, and even SQUIDs have been published to this date. In this thesis, the feasibility of high-field magnet applications of FBS is addressed by studying their transport properties, involving doped BaFe{sub 2}As{sub 2} (Ba-122) and LnFeAs(O,F) [Ln=Sm and Nd]. Particularly, it is important to study physical properties in a sample form (i.e. thin films) that is close to the conditions found in applications. However, the realisation of epitaxial FBS thin films is not an easy undertaking. Recent success in growing epitaxial FBS thin films opens a new avenue to delve into transport critical current measurements. The information obtained through this research will be useful for exploring high-field magnet applications. This thesis consists of 7 chapters: Chapter 1 describes the motivation of this study, the basic background of superconductivity, and a brief summary of the thin film growth of FBS. Chapter 2 describes experimental methods employed in this study. Chapter 3 reports on the fabrication of Co-doped Ba-122 thin films on various substrates. Particular emphasis lies on the discovery of fluoride substrates to be beneficial for

Growth orientation and superconducting properties of YBa2Cu3O7-δ films prepared by the low-fluorine sol-gel process

International Nuclear Information System (INIS)

Lei Li; Zhao Gaoyang; Xu Hui; Zhao Juanjuan

2010-01-01

YBa 2 Cu 3 O 7-δ (YBCO) films were deposited on (100)-oriented LaAlO 3 (LAO) single crystal substrates by the dip-coating process using low-fluorine solution. Their microstructures were characterized with the aid of X-ray diffractometry, scanning electron microscopy and high-resolution transmission electron microscopy. Their superconducting properties were measured by the standard four-probe method. The experiment results show that the film obtained under high enough humidity conditions exhibits better c-axis texture and superconducting properties than the film under a relatively low humidity conditions. Based on the classical nucleation and chemical reaction thermodynamics theory, the underlying crystalline and growth mechanisms of YBCO films under certain humidity conditions are explained in combination with our experimental results. It is suggested that the unreacted intermediate phases such as BaF 2 and CuO aggregated in the YBCO grain boundary will cause lattice distortion in the YBCO matrix and further induce the formation of a-axis oriented YBCO grains as crystallization proceeds. Therefore, it is believed that the relative content of water vapor within the heat-treatment atmosphere plays quite an important role in the preparation of c-axis oriented YBCO film with good superconducting properties. (semiconductor materials)
Effects of argon implantation and vacuum annealing of the superconducting properties of single-crystal niobium films

International Nuclear Information System (INIS)

Zakirov, R.M.; Kuznetsov, V.P.; Shermergor, T.D.

1980-01-01

Characteristics of superconducting transition (Tsub(K), Hsub(perpendicular)) of monocrystalline niobium films on sapphire, irradiated by 35 keV Ar ions within 0.62x10 15 -5.6x10 16 ion/cm 2 dose range, are investigated. Introduction of argon atoms results in Tsub(K) decrease of films and rhosub(n), Hsub(perpendicular 0) and dHsub(perpendicular)/dT increase due to reduction of free path length of electrons. Shown is an essential difference in the behaviour of superconducting parameters of irradiated monocrystalline niobium films and films with niobium, dassol ved in the niobium lattice. Introduction of oxygen has been carried out by annealing of films in vacuum after their heating in the air
Superconducting thin films of YBa2Cu3O7-x

International Nuclear Information System (INIS)

Hudner, J.

1993-01-01

Thin films of the high temperature superconductor YBa 2 Cu 3 O 7-x (YBCO) are of significance in fundamental studies of oxide superconductors and for prospected electronic applications based on superconductors operating at liquid nitrogen temperatures (T= 77 K). Synthesis of YBCO thin films is complex and a large part of this thesis has been devoted to the elaboration of various techniques in forming YBCO thin films. A general observation was that synthesis of YBCO films exhibiting high zero-resistivity temperatures temperatures (T c ) ≥ 88 K and elevated critical current densities (J c ) ≥ 10 6 A/cm 2 at 77 K was possible under widely different conditions of film growth. For the BaF 2 -based method, various substrate materials were investigated. Among perovskite related substrates with low losses in the high frequency regime, LaA10 3 was found to yield YBCO films exhibiting the highest quality electrical properties. A study of YBCO film interaction with sapphire substrates was performed. It was suggested that the YBCO film on sapphire consists of weakly coupled superconducting grains. Compositional effects of Y, BA and Cu for MOCVD-YBCO films were examined with respect to morphology, structure, resistivity, as susceptibility and J c (T). High T c :s and J c :s were observed for an anomalous large compositional range of Cu in off-compositional YBCO films. This was shown to be related to the formation of Cu-rich precipitates embedded within a c-Axis oriented stoichiometric YBCO film matrix. Thermal critical current behavior at zero field in thin films of YBCO fabricated by various methods has been studied by three techniques: transport measurements on patterned microbridges, dc magnetization hysteresis loops using the Bean model and non-linear ac susceptibility analysis. Absolute critical current values obtained form the two former techniques when measured on the same YBCO film were observed to differ about a factor of two. The feasibility of non-linear ac
Electronic properties of high Tc superconductors

International Nuclear Information System (INIS)

Rojo, A.G.

1989-01-01

Using analytical and numerical methods, the electronic properties of the copper-oxygen plane in the normal phase of high Tc superconductors are described. Using the slave-boson technique in the saddle point, a theory of the metal insulator transition which generalizes the notions of a Mott insulator to the case of more than a single band for those planes is presented. A phase-diagram is obtained in the parameter space and effective masses, optical gaps and metallization are calculated as a function of the number of carriers. Based on the experimental evidence, the theory permits classification of superconducting compounds as charge transfer insulators in the stoichiometric case. The insulator state is characterized by a non-zero optical gap and a divergent effective mass which corresponds to the breakage of a Fermi-liquid scheme. The results obtained are applicable to metal-transition-oxides whose behaviour has been traditionally controversial and it is concluded that it is necessary to broaden the meaning of a Mott insulator to the case of more than a single band to better understand them. Based on the ideas of group renormalization in a real space, a lattice approximation is presented, which allows: a) To complement the treatment of slave-bosons in phase diagrams and optical gaps; b) Identification of an attraction mechanism between carriers originating from purely repulsive interactions. Numerical calculations in small clusters show the existence of a pairing mechanism showing a superconducting instability from a charge transfer insulator. (Author) [es
Spin-polaron theory of high-Tc superconductivity: I, spin polarons and high-Tc pairing

International Nuclear Information System (INIS)

Wood, R.F.

1993-06-01

The concept of a spin polaron is introduced and contrasted with the more familiar ionic polaron picture. A brief review of aspects of ionic bipolaronic superconductivity is given with particular emphasis on the real-space pairing and true Bose condensation characteristics. The formation energy of spin polarons is then calculated in analogy with ionic polarons. The spin-flip energy of a Cu spin in an antiferromagnetically aligned CuO 2 plane is discussed. It is shown that the introduction of holes into the CuO 2 planes will always lead to the destruction of long-range AF ordering due to the formation of spin polarons. The pairing of two spin polarons can be expected because of the reestablishment of local (short-range) AF ordering; the magnitude of the pairing energy is estimated using a simplified model. The paper closes with a brief discussion of the formal theory of spin polarons
Response of fractal penetration of magnetic flux to disorder landscape in superconducting films

Science.gov (United States)

Ye, Zuxin; Li, Qiang; Si, W. D.; Suenaga, M.; Solovyov, V. F.; Johnson, P. D.

2005-10-01

Magnetic flux front and induction contours in superconducting YBa2Cu3O7-δ films with defect size stilde ξ (superconducting coherence length) and s≫ξ are studied by magneto-optical imaging. Robust self-affine spatial correlation was observed using scaling analysis in the small pinning disorder-dominated ( stilde ξ) films. The roughness exponent α was determined to be ˜0.66 , independent of numbers of defects (or the film thickness). When the disorder landscape also included a distribution of large defects (s≫ξ) , the flux front and induction contours exhibited self-similarity, with a fractal dimension D determined to be ˜1.33 using the box-counting method. The remarkably different flux penetration patterns were shown to be the manifestation of self-organized criticality at different length scales.
Effective valence as the control parameter of the superconducting ...

African Journals Online (AJOL)

One approach to investigating the superconductivity in the ironbased materials is understanding the chemical and structural parameters that can be used to tune their remarkably high Tc. In this paper, we have demonstrated that the effective valence of iron can be used as the control parameter to tune the Tc of this family of ...
Superconducting technology program Sandia 1996 annual report

International Nuclear Information System (INIS)

Roth, E.P.

1997-02-01

Sandia's Superconductivity Technology Program is a thallium-based high-temperature superconductor (HTS) research and development program consisting of efforts in powder synthesis and process development, open-system thick film conductor development, wire and tape fabrication, and HTS motor design. The objective of this work is to develop high-temperature superconducting conductors (wire and tape) capable of meeting requirements for high-power electrical devices of interest to industry. The research efforts currently underway are: (1) Process development and characterization of thallium-based high-temperature superconducting closed system wire and tape, (2) Investigation of the synthesis and processing of thallium-based thick films using two-zone processing, and (3) Cryogenic design of a 30K superconducting motor. This report outlines the research that has been performed during FY96 in each of these areas
What is strange about high-temperature superconductivity in cuprates?

Science.gov (United States)

Božović, I.; He, X.; Wu, J.; Bollinger, A. T.

2017-10-01

Cuprate superconductors exhibit many features, but the ultimate question is why the critical temperature (Tc) is so high. The fundamental dichotomy is between the weak-pairing, Bardeen-Cooper-Schrieffer (BCS) scenario, and Bose-Einstein condensation (BEC) of strongly-bound pairs. While for underdoped cuprates it is hotly debated which of these pictures is appropriate, it is commonly believed that on the overdoped side strongly-correlated fermion physics evolves smoothly into the conventional BCS behavior. Here, we test this dogma by studying the dependence of key superconducting parameters on doping, temperature, and external fields, in thousands of cuprate samples. The findings do not conform to BCS predictions anywhere in the phase diagram.
Temperature dependence of the experimental penetration depth of superconducting thin films

International Nuclear Information System (INIS)

Fink, H.J.; Gruenfeld, V.; Pastawski, H.

1982-01-01

Experimental magnetic field penetration depths delta(t,d,H) of the stable and superheated Meissner state were calculated as a function of temperature for various applied magnetic fields and various film thicknesses for two cases: (1) lambda(t)/d<< kappa→infinity and (2) kappa< or approx. =2lambda(t)/d (lambda is the Ginzburg-Landau penetration depth, d is the film thickness, kappa is the GL parameter). The results of the first case should be a useful tool for obtaining lambda(0) of amorphous superconducting thin films
A study on the effect of tantalum-impurity content on the superconducting properties of niobium materials used for making superconducting radio frequency cavities

Science.gov (United States)

Roy, S. B.; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Tiwari, M. K.; Lodha, G. S.; Myneni, G. R.

2012-11-01

Niobium materials in highly pure form are used in the fabrication of superconducting radio frequency cavities. We present here a study of the superconducting properties of such niobium materials that have been used in the fabrication of high accelerating gradient superconducting radio frequency cavities after determining their tantalum-impurity contents using a synchrotron-based x-ray fluorescence spectroscopy technique. Our results show that there is a small change in superconducting parameters such as TC,HC1 and HC2 when the tantalum-impurity content varies from ≈150 to ≈1300 ppm. In contrast, a buffered chemical polishing of the same niobium samples changes all these superconducting parameters more significantly. The implications of these results on the performance of niobium superconducting radio frequency cavities are discussed.
Characterization of 3-dimensional superconductive thin film components for gravitational experiments in space

Energy Technology Data Exchange (ETDEWEB)

Hechler, S.; Nawrodt, R.; Nietzsche, S.; Vodel, W.; Seidel, P. [Friedrich-Schiller-Univ. Jena (Germany). Inst. fuer Festkoerperphysik; Dittus, H. [ZARM, Univ. Bremen (Germany); Loeffler, F. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

2007-07-01

Superconducting quantum interference devices (SQUIDs) are used for high precise gravitational experiments. One of the most impressive experiments is the satellite test of the equivalence principle (STEP) of NASA/ESA. The STEP mission aims to prove a possible violation of Einstein's equivalence principle at an extreme level of accuracy of 1 part in 10{sup 18} in space. In this contribution we present an automatically working measurement equipment to characterize 3-dimensional superconducting thin film components like i.e. pick-up coils and test masses for STEP. The characterization is done by measurements of the transition temperature between the normal and the superconducting state using a special built anti-cryostat. Above all the setup was designed for use in normal LHe transport Dewars. The sample chamber has a volume of 150 cm{sup 3} and can be fully temperature controlled over a range from 4.2 K to 300 K with a resolution of better then 100 mK. (orig.)
Superconductivity and low temperature electrical transport in B-doped CVD nanocrystalline diamond

Directory of Open Access Journals (Sweden)

Milos Nesladek, Jiri J. Mares, Dominique Tromson, Christine Mer, Philippe Bergonzo, Pavel Hubik and Jozef Kristofik

2006-01-01

Full Text Available In this work, we report on superconductivity (SC found in thin B-doped nanocrystalline diamond films, prepared by the PE-CVD technique. The thickness of the films varies from about 100 to 400 nm, the films are grown on low-alkaline glass at substrate temperatures of about 500–700 °C. The SIMS measurements show that films can be heavily doped with boron in concentrations in the range of 3×1021 cm−3. The Raman spectra show Fano resonances, confirming the substitutional B-incorporation. The low temperature magnetotransport measurements reveal a positive magnetoresistance. The SC transition is observed at about Tc=1.66 K. A simple theory exploiting the concept of weak localization accounting for this transition is proposed.
Superconductores de alta Tc, diez años después

Directory of Open Access Journals (Sweden)

A. Mariño Camargo

1996-07-01

Full Text Available This contribution is a short review of the current state of the high temperature superconductivity. After ten years of research in this field. A description of the common characteristics of the new sllperconducting materials is followed by the discussion of so me releva nt problems that limit their applications. Sorne aspects related to the determination of the mechanisms responsibles for the high Tc superconductivity are mentioned.
Superconductivity and spin fluctuations

International Nuclear Information System (INIS)

Scalapino, D.J.

1999-01-01

The organizers of the Memorial Session for Herman Rietschel asked that the author review some of the history of the interplay of superconductivity and spin fluctuations. Initially, Berk and Schrieffer showed how paramagnon spin fluctuations could suppress superconductivity in nearly-ferromagnetic materials. Following this, Rietschel and various co-workers wrote a number of papers in which they investigated the role of spin fluctuations in reducing the Tc of various electron-phonon superconductors. Paramagnon spin fluctuations are also believed to provide the p-wave pairing mechanism responsible for the superfluid phases of 3 He. More recently, antiferromagnetic spin fluctuations have been proposed as the mechanism for d-wave pairing in the heavy-fermion superconductors and in some organic materials as well as possibly the high-Tc cuprates. Here the author will review some of this early history and discuss some of the things he has learned more recently from numerical simulations
A study on the development of high-Tc superconducting wire

International Nuclear Information System (INIS)

Won, Dong Yeon; Lee, Hee Gyoun; Kim, Chan Joong

1991-09-01

High magnetization YBaCuO superconductor was prepared with additions of BaSnO 3 , SnO 2 and SiC by partial melt processing. Addition of BaSnO 3 increased the magnetic property of YBaCuO by flux pinning action of finely dispersed BaSnO 3 particles, while addition of SnO 2 decreased the magnetic property, because the size of particle was larger than that of BaSnO 3 . BiPbSrCaCuO superconducting tape of single filament was prepared by powder-in-tube method using silver as a shearth material. The fabrication techniques involves powder packing, swaging, drawing and cold rolling/pressing method. The final dimension of wire after drawing is 1.2mm diameter. The wire was pressed into a tape form with a thickness of 70micron and a width of 3mm. The obtained critical current density of the prepared tape was 2000A/cm 2 at 77K. (Author)
Superconductivity in Na{sub 1-x}CoO{sub 2}.yH{sub 2}O thin films

Energy Technology Data Exchange (ETDEWEB)

Hildebrandt, Sandra; Komissinkiy, Philipp; Alff, Lambert [Institute for Materials Science, TU Darmstadt (Germany); Fritsch, Ingo; Habermeier, Hanns-Ulrich [Max-Planck-Institute for Solid State Research, Stuttgart (Germany); Lemmens, Peter [Institute for Condensed Matter Physics, TU Braunschweig (Germany)

2010-07-01

Sodium cobaltate (Na{sub 1-x}CoO{sub 2}) is a novel material with thermoelectric behavior, charge and spin ordered states dependent on the sodium content in the composition. A superconducting phase was found in water intercalated sodium cobaltate (Na{sub 1-x}CoO{sub 2}.yH{sub 2}O) with x=0.65-0.7 and y=0.9-1.3. The pairing state is still under debate, but there are some indications for a spin-triplet or p-wave superconducting pairing state. First films of Na{sub 1-x}CoO{sub 2}.yH{sub 2}O with a superconducting transition temperature near 5 K have been successfully grown. Here we report on thin films of Na{sub 1-x}CoO{sub 2} grown by pulsed laser deposition technique. The deposition parameters, sodium deintercalation and water intercalation conditions are tuned in order to obtain the superconducting phase. The instability of this phase might be an indication for triplet superconductivity, which is known to be affected strongly by impurities and defects.This observation is in agreement with the fact that so far also no superconducting thin films of the most famous triplet superconductor Sr{sub 2}RuO{sub 4} have been reported.
Materials for superconducting cavities

International Nuclear Information System (INIS)

Bonin, B.

1996-01-01

The ideal material for superconducting cavities should exhibit a high critical temperature, a high critical field, and, above all, a low surface resistance. Unfortunately, these requirements can be conflicting and a compromise has to be found. To date, most superconducting cavities for accelerators are made of niobium. The reasons for this choice are discussed. Thin films of other materials such as NbN, Nb 3 Sn, or even YBCO compounds can also be envisaged and are presently investigated in various laboratories. It is shown that their success will depend critically on the crystalline perfection of these films. (author)
Superconductivity in bundles of double-wall carbon nanotubes.

Science.gov (United States)

Shi, Wu; Wang, Zhe; Zhang, Qiucen; Zheng, Yuan; Ieong, Chao; He, Mingquan; Lortz, Rolf; Cai, Yuan; Wang, Ning; Zhang, Ting; Zhang, Haijing; Tang, Zikang; Sheng, Ping; Muramatsu, Hiroyuki; Kim, Yoong Ahm; Endo, Morinobu; Araujo, Paulo T; Dresselhaus, Mildred S

2012-01-01

We present electrical and thermal specific heat measurements that show superconductivity in double-wall carbon nanotube (DWCNT) bundles. Clear evidence, comprising a resistance drop as a function of temperature, magnetoresistance and differential resistance signature of the supercurrent, suggest an intrinsic superconducting transition below 6.8 K for one particular sample. Additional electrical data not only confirm the existence of superconductivity, but also indicate the T(c) distribution that can arise from the diversity in the diameter and chirality of the DWCNTs. A broad superconducting anomaly is observed in the specific heat of a bulk DWCNT sample, which yields a T(c) distribution that correlates well with the range of the distribution obtained from the electrical data. As quasi one dimensionality of the DWCNTs dictates the existence of electronic density of state peaks, confirmation of superconductivity in this material system opens the exciting possibility of tuning the T(c) through the application of a gate voltage.
Superconductivity mediated by quantum critical antiferromagnetic fluctuations: The rise and fall of hot spots

Science.gov (United States)

Wang, Xiaoyu; Schattner, Yoni; Berg, Erez; Fernandes, Rafael M.

2017-05-01

In several unconventional superconductors, the highest superconducting transition temperature Tc is found in a region of the phase diagram where the antiferromagnetic transition temperature extrapolates to zero, signaling a putative quantum critical point. The elucidation of the interplay between these two phenomena—high-Tc superconductivity and magnetic quantum criticality—remains an important piece of the complex puzzle of unconventional superconductivity. In this paper, we combine sign-problem-free quantum Monte Carlo simulations and field-theoretical analytical calculations to unveil the microscopic mechanism responsible for the superconducting instability of a general low-energy model, called the spin-fermion model. In this approach, low-energy electronic states interact with each other via the exchange of quantum critical magnetic fluctuations. We find that even in the regime of moderately strong interactions, both the superconducting transition temperature and the pairing susceptibility are governed not by the properties of the entire Fermi surface, but instead by the properties of small portions of the Fermi surface called hot spots. Moreover, Tc increases with increasing interaction strength, until it starts to saturate at the crossover from hot-spots-dominated to Fermi-surface-dominated pairing. Our work provides not only invaluable insights into the system parameters that most strongly affect Tc, but also important benchmarks to assess the origin of superconductivity in both microscopic models and actual materials.

Stoichiometric transfer of material in the infrared pulsed laser deposition of yttrium doped Bi-2212 films

International Nuclear Information System (INIS)

De Vero, Jeffrey C.; Blanca, Glaiza Rose S.; Vitug, Jaziel R.; Garcia, Wilson O.; Sarmago, Roland V.

2011-01-01

Highlights: → This work describes the stoichiometric transfer of Y-doped Bi-2212 during IR-PLD. → As-deposited films show spheroidal morphology with similar composition as the target. Relatively flat and highly c-axis oriented films were obtained after heat treatment. → IR-PLD can be a viable technique in growing other high Tc superconducting materials. - Abstract: Films of Y-doped Bi-2212 were successfully grown on MgO (1 0 0) substrates by infrared pulsed laser deposition (IR-PLD). With post-heat treatments, smooth and highly c-axis oriented films were obtained. The average compositions of the films have the same stoichiometry as the target. Y content is also preserved on the grown films at all doping levels. The electrical properties of the grown Y-doped Bi-2212 films exhibit the expected electrical properties of the bulk Y-doped Bi-2212. This is attributed to the stoichiometric transfer of material by IR-PLD.
Hall effect in high- Tc Y 1Ba 2Cu 3O 7-δ superconductor

Science.gov (United States)

Vezzoli, G. C.; Burke, T.; Moon, B. M.; Lalevic, B.; Safari, A.; Sundar, H. G. K.; Bonometti, R.; Alexander, C.; Rau, C.; Waters, K.

1989-04-01

We have performed point-by-point and continuous Hall effect experiments as a function of temperature in polycrystalline Y 1Ba 2Cu 3O 7-δ. We have shown that the positive Hall constant shows an abrupt increase upon decreasing temperature at a value just above Tc. This temperature corresponds to where the resistance versus temperature data deviates from linearity. At very high fields of 6.8 and 15 T we observe a subsequent decrease in RH. We interpret these data as supportive of a contribution toward the superconductivity mechanism arising from internal excitions or change transfer excitations such that the bound exciton concentration increases near Tc at the expense of positive carries which are reflected in both bound and free holes.
Stability of Tl-Ba-Ca-Cu-O Superconducting Thin Films

Energy Technology Data Exchange (ETDEWEB)

Siegal, M.P.; Overmyer, D.L.; Venturini, E.L.; Padilla, R.R.; Provencio, P.N.

1999-08-23

We report the stability of TlBa{sub 2}CaCu{sub 2}O{sub 7} (Tl-1212) and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} (T1-2212) thin films and by inference, the stability of TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 9} (Tl-1223) and Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} (Tl-2223) thin films, under a variety of conditions. In general, we observe that the stability behavior of the single Tl-O layer materials (Tl-1212 and Tl-1223)are similar and the double Tl-O layer materials (Tl-2212 and Tl-2223) are similar. All films are stable with repeated thermal cycling to cryogenic temperatures. Films are also stable in acetone and methanol. Moisture degrades film quality rapidly, especially in the form of vapor. Tl-1212 is more sensitive to vapor than Tl-2212. These materials are stable to high temperatures in either N{sub 2}, similar to vacuum for the cuprates, and O{sub 2} ambients. While total degradation of properties (superconducting and structural) occur at the same temperatures for all phases, 600 C in N{sub 2} and 700 C in O{sub 2}, the onset of degradation occurs at somewhat lower temperatures for Tl-1212 than for Tl-2212 films. In all cases, sample degradation is associated with Tl depletion from the films.
Probing the local microwave properties of superconducting thin films by a scanning microwave near-field microscope

CERN Document Server

Wu, L Y; Wang, K L; Jiang, T; Kang, L; Yang, S Z; Wu, P H

2002-01-01

In this paper, we present our approach to probe the local microwave properties of superconducting thin films by using the microwave near-field scanning technique. We have employed a coaxial cavity together with a niobium tip as the probe and established a scanning sample stage cooled by liquid nitrogen to study thin film devices at low temperature in our scanning microwave near-field microscope. Nondestructive images have been obtained on the inhomogeneity of the YBaCuO superconducting thin films at microwave frequency. We believe that these results would be helpful in evaluating the microwave performance of the devices.
Electrical Transport Through Tunnel Barriers and Thin Dielectric Layers and Physical Properties of the High Tc Oxide Superconductors

Science.gov (United States)

1990-03-26

Josephson Tipo Emparedado con Barrera de (Nb-Si)-Amorto," PhD. Thesis, Universidad Nacional Autonoma de Mexico, May 1989. 17. E.S. Hellman, D.G...A15 Nb-Sn," Phys. Rev. B 30, p. 2590 (1984). 4. S.J. Bending, R.H. Hammond, and M.R. Beasley, "Superconductivity in the High-Tc A15 V-6a System," Bull
Specific heat measurement set-up for quench condensed thin superconducting films.

Science.gov (United States)

Poran, Shachaf; Molina-Ruiz, Manel; Gérardin, Anne; Frydman, Aviad; Bourgeois, Olivier

2014-05-01

We present a set-up designed for the measurement of specific heat of very thin or ultra-thin quench condensed superconducting films. In an ultra-high vacuum chamber, materials of interest can be thermally evaporated directly on a silicon membrane regulated in temperature from 1.4 K to 10 K. On this membrane, a heater and a thermometer are lithographically fabricated, allowing the measurement of heat capacity of the quench condensed layers. This apparatus permits the simultaneous thermal and electrical characterization of successively deposited layers in situ without exposing the deposited materials to room temperature or atmospheric conditions, both being irreversibly harmful to the samples. This system can be used to study specific heat signatures of phase transitions through the superconductor to insulator transition of quench condensed films.
Surface characterization of superconductive Nd1Ba2Cu3Oy thin films using scanning probe microscopes

International Nuclear Information System (INIS)

Ting, W.; Badaye, M.; Itti, R.; Morishita, T.; Koshizuka, N.; Tanaka, S.

1996-01-01

Recently, superconductive Nd 1 Ba 2 Cu 3 O y (Nd123) thin films with high superconducting transition temperature (T c ) have been successfully fabricated at the authors institute employing the standard laser ablation method. In this paper, they report parts of the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode at the final growing stage. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half integer numbers of the c-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive, or sometimes even metallic. The results of STS measurements together with the fact that they are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films
Specific feature of critical fields of inhomogeneous superconducting films

International Nuclear Information System (INIS)

Glazman, L.I.; Dmitrenko, I.M.; Kolin'ko, A.E.; Pokhila, A.S.; Fogel', N.Ya.; Cherkasova, V.G.

1988-01-01

Experimental studies on thin vanadium films (d=250-400 A) have revealed anomaly in the temperature dependence of the upper critical field H cparallel (T), when H is parallel to the sample plane. At certain temperature T 0 the dependence H cparallel 2 (T) has a sharp kink separating two linear portions. The anomalous behaviour of H cparallel (T) of thin V films can be accounted for assuming the film separation into two parallel layers having different parameters (critical temperature T c , coherence length ξ, thickness d). At temperatures above and lower T 0 the dependence H cparallel (T) is mainly dependent on the characteristics of only one layer. The kink in the dependence H cparallel 2 (T) is due to a jump-like transition of the superconducting nucleus from one layer to the other at T c . The anomalous behaviour of the dependence H cparallel (T) is also observed in sandwiches consisting of two identical films separated with a high (about 30 A) dielectric interlayer; however, the transition from one linear portion to the other is smooth. In the case of identical films a specific crossover occurs if at T-T c the critical field H cparallel (T) coinsides with that for the layer of doubled thickness, then at lowering temperature H cparallel (T) asymptotically approaches the critical field of one layer. The calculation within the model described provides a good description for the experimental results
Quantitative determination of high-Tc superconductivity from the lattice polarization, structure effect and approach to 300 K Tc

International Nuclear Information System (INIS)

Green, B.A.

1997-01-01

The quasiparticle state defined by the low temperature polar mobility is a large, quantized positive energy shift that is identical to the constant pairing energy (pseudogap and 2Λ) in the multi-plane high-T c superconductors, showing the lattice polarization produces the single-particle shift and pairing which then transfer to the superconducting state. The coupling-independence and state transfer follow from the nonlocality and action length of the polarization interaction, and the multiple plane requirement from the location of the polar mode. 2Δ is thereby obtained directly, without scaling, from the strong interaction on the plane. The interaction accordingly produces a dynamic, highly stable state, in contrast to BCS superconductors, and the zero-order state is the quantized energy shift. (orig.)
The effects of Fe2O3 nanoparticles on MgB2 superconducting thin films

International Nuclear Information System (INIS)

Koparan, E.T.; Sidorenko, A.; Yanmaz, E.

2013-01-01

Full text: Since the discovery of superconductivity in binary MgB 2 compounds, extensive studies have been carried out because of its excellent properties for technological applications, such as high transition temperature (T c = 39 K), high upper critical field (H c2 ), high critical current density (J c ). Thin films are important for fundamental research as well as technological applications of any functional materials. Technological applications primarily depend on critical current density. The strong field dependence of J c for MgB 2 necessitates an enhancement in flux pinning performance in order to improve values in high magnetic fields. An effective way to improve the flux pinning is to introduce flux pinning centers into MgB 2 through a dopant having size comparable to the coherence length of MgB 2 . In this study, MgB 2 film with a thickness of about 600 nm was deposited on the MgO (100) single crystal substrate using a 'two-step' synthesis technique. Firstly, deposition of boron thin film was carried out by rf magnetron sputtering on MgO substrates and followed by a post deposition annealing at 850 degrees Celsius in magnesium vapour. In order to investigate the effect of Fe 2 O 3 nanoparticles on the structural and magnetic properties of films, MgB 2 films were coated with different concentrations of Fe 2 O 3 nanoparticles by a spin coating process. The effects of different concentrations of ferromagnetic Fe 2 O 3 nanoparticles on superconducting properties of obtained films were carried out by using structural (XRD, SEM, AFM), electrical (R-T) and magnetization (M-H, M-T and AC Susceptibility) measurements. It was calculated that anisotropic coefficient was about γ = 1.2 and coherence length of 5 nm for the uncoated film. As a result of coherence length, the appropriate diameters of Fe 2 O 3 nanoparticles were found to be 10 nm, indicating that these nanoparticles served as the pinning centers. Based on the data obtained from this study, it can be
Properties of lift-off structured high Tc microbridges

NARCIS (Netherlands)

Hauser, B.; Klopman, B.; Blank, David H.A.; Rogalla, Horst

1989-01-01

Microbridges and DC SQUIDs (superconducting quantum interference devices) were fabricated, using a lift-off technique, from RF sputtered YBaCuO films on MgO single-crystal substrates. Microwave measurements at 9 GHz on microbridges and the magnetic-field dependence of their critical current reveal
Compositional analysis of YBaCuO superconducting films with ion beam analysis techniques

International Nuclear Information System (INIS)

Jones, S.; Timmers, H.; Ophel, T.R.; Elliman, R.G.

1999-01-01

High-T c YBa x Cu y O 7-δ superconducting films are being developed for applications such as superconducting quantum interference devices. The carrier concentration, critical current density J c and critical temperature T c of these films depend sensitively on the oxygen content . Stoichiometry, uniformity with depth, homogeneity across the sample and film thickness are also important quantities for their characterisation. It has been shown, for example, that the stoichiometry of the metallic elements affects the growth characteristics and surface morphology of the films. With the deposit ion techniques used, reproducibility of film properties is difficult. The characterisation of YBa x Cu y O 7-δ films with ion beam analysis techniques is complex. Whereas the three metallic elements can be detected with helium beams and Rutherford Backscattering (RBS), the oxygen signal is generally obscured by that from substrate elements. It can be better detected using resonant backscattering with 3.04MeV 4 He ions or nuclear reaction analysis. Elastic Recoil Detection (ERD) with high-energetic (1MeV/amu), heavy beams (Z > 120), enables all elements to be detected and separated in a single experiment. It is well established that ion bombardment induces vacancies in the oxygen sub-lattice, driving the material to change from crystalline to amorphous, the latter phase having a reduced oxygen content. In previous heavy ion ERD measurements of YBa x Cu yO z films with 200MeV 127 I beams, the opaque films became transparent in the beam spot area, indicative of the amorphous phase. The accuracy of the oxygen measurement is therefore questionable. Indeed, using Raman spectroscopy, distortions of the crystalline structure above a fluence of 5 x 10 11 ion/cm 2 and for higher doses some signatures of a reduction in oxygen content have been observed for such beams. It appears therefore that a correct determination of the oxygen content requires either a drastic reduction in fluence or a
Two-dimensional superconductivity in ultrathin disordered thin films

International Nuclear Information System (INIS)

Beasley, M.R.

1992-01-01

The status of the understanding of two-dimensional superconductivity in ultrathin, disordered thin films is reviewed. The different consequences of microscopic versus macroscopic disorder are stressed. It is shown that microscopic disorder leads to a rapid suppression of the mean-field transition temperature. The consequences of macroscopic disorder are not well understood, but a universal behavior of the zero-bias resistance as a function of field and temperature has been observed. (orig.)
Microwave testing of high-Tc based direct current to a single flux quantum converter

DEFF Research Database (Denmark)

Kaplunenko, V. K.; Fischer, Gerd Michael; Ivanov, Z. G.

1994-01-01

Design, simulation, and experimental investigations of a direct current to a single flux quantum converter loaded with a Josephson transmission line and driven by an external 70 GHz microwave oscillator are reported. The test circuit includes nine YBaCuO Josephson junctions aligned on the grain...... boundary of a 0°–32° asymmetric Y-ZrO2 bicrystal substrate. The performance of such converters is important for the development of the fast Josephson samplers required for testing of high-Tc rapid single flux quantum circuits in high-speed digital superconducting electronics. Journal of Applied Physics...
Project in fiscal 1989 for research and development of basic technologies in next generation industries. Research and development of superconducting materials and superconducting elements (Achievement report on forecast and research of superconducting element technology); 1990 nendo chodendo soshi gijutsu yosoku kenkyu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1991-03-01

With an objective to forecast the ways the future superconducting elements and the related technologies should proceed, investigations and researches were performed on the progress in research and development of high-temperature superconducting elements, and the superconduction in a wide range. This paper summarizes the achievements in fiscal 1990. The high-temperature superconducting thin film technology has made remarkable advancement. The correlation of film forming conditions with characteristics of thin films was studied by using the sputtering process, laser deposition process and CVD process, having made production of thin films sufficiently applicable to electronics possible. A technology has been developed to suppress deterioration of characteristics for high-temperature conductors in thin film patterning, surface treatment and lamination structure fabrication. However, the problem of characteristics deterioration on interface of tri-terminal elements still remain unsolved. The bonded structure elements using high-temperature superconductors is the central technology in electronics application, but such problems exist as the coherence length being short, deterioration of characteristics at interfaces, and the electric characteristics being sensitive to crystalline orientation. Technological development to overcome these problems is under way. (NEDO)
Correlation effects in high-Tc superconductors and heavy fermion compounds

International Nuclear Information System (INIS)

Kuzemsky, A.L.

1993-10-01

This paper describes certain aspects of Highly Correlated Systems (HCS) such as high Tc superconductors (HTSC) and some new class of Heavy Fermion (HF) systems which have been studied recently. The problem is discussed on how the charge and spin degrees of freedom participate in the specific character of superconductivity in the copper oxides and competition of the magnetism and Kondo screening in heavy fermions. The electronic structure and possible superconducting mechanisms of HTSC compounds are discussed. The similarity and dissimilarity with HF compounds is pointed out. It is shown that the spins and carriers in the copper oxides are coupled in a very nontrivial way in order to introduce the discussion and the comparison of the Emery model, the t - J-model and the Kondo-Heisenberg model. It concerns attempts to derive from fundamental multi-band Hamiltonian the reduced effective Hamiltonians to extract and separate the relevant low-energy physics. A short review of the arguments which seem to support the spin-polaron pairing mechanism in HTSC are presented. Many other topics like the idea of mixed valence states in oxides, the role of charge transfer (CT) excitations, phase separation, self-consistent nonperturbative technique, etc. are also discussed. (author). 161 refs
Control of superconductivity by means of electric-field-induced strain in superconductor/piezoelectric hybrids

Science.gov (United States)

Stamopoulos, D.; Zeibekis, M.; Zhang, S. J.

2018-01-01

The controlled modification of superconductivity by any means, specifically in hybrid systems, has attracted much interest in the recent decades. Here, we present experimental data and phenomenological modeling on the control of TC of superconducting (SC) Nb thin films, with thickness 3 nm ≤ dN b≤50 nm, under the application of in-plane strain, S(Eex) induced by an external out-of-plane electric field, Eex to piezoelectric (PE) single crystals, namely, ( 1 -x )Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT), with x = 0.27 and 0.31. We report experimental modification of TC of Nb by Eex, accurately described by a phenomenological model that incorporates the constitutive relation S(Eex) of PMN-xPT. The systematic experimental-phenomenological modeling approach introduced here is generic and paves the way for an understanding of the underlying physical mechanisms in any SC/PE hybrid.
Collective excitations and superconductivity in reduced dimensional systems - Possible mechanism for high Tc

International Nuclear Information System (INIS)

Santoyo, B.M.

1989-01-01

The author studies in full detail a possible mechanism of superconductivity in slender electronic systems of finite cross section. This mechanism is based on the pairing interaction mediated by the multiple modes of acoustic plasmons in these structures. First, he shows that multiple non-Landau-damped acoustic plasmon modes exist for electrons in a quasi-one dimensional wire at finite temperatures. These plasmons are of two basic types. The first one is made up by the collective longitudinal oscillations of the electrons essentially of a given transverse energy level oscillating against the electrons in the neighboring transverse energy level. The modes are called Slender Acoustic Plasmons or SAP's. The other mode is the quasi-one dimensional acoustic plasmon mode in which all the electrons oscillate together in phase among themselves but out of phase against the positive ion background. He shows numerically and argues physically that even for a temperature comparable to the mode separation Δω the SAP's and the quasi-one dimensional plasmon persist. Then, based on a clear physical picture, he develops in terms of the dielectric function a theory of superconductivity capable of treating the simultaneous participation of multiple bosonic modes that mediate the pairing interaction. The effect of mode damping is then incorporated in a simple manner that is free of the encumbrance of the strong-coupling, Green's function formalism usually required for the retardation effect. Explicit formulae including such damping are derived for the critical temperature T c and the energy gap Δ 0 . With those modes and armed with such a formalism, he proceeds to investigate a possible superconducting mechanism for high T c in quasi-one dimensional single-wire and multi-wire systems
Loss mechanisms in superconducting thin film microwave resonators

Energy Technology Data Exchange (ETDEWEB)

Goetz, Jan, E-mail: jan.goetz@wmi.badw.de; Haeberlein, Max; Wulschner, Friedrich; Zollitsch, Christoph W.; Meier, Sebastian; Fischer, Michael; Fedorov, Kirill G.; Menzel, Edwin P. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany); Deppe, Frank; Eder, Peter; Xie, Edwar; Gross, Rudolf, E-mail: rudolf.gross@wmi.badw.de [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany); Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 München (Germany); Marx, Achim [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany)

2016-01-07

We present a systematic analysis of the internal losses of superconducting coplanar waveguide microwave resonators based on niobium thin films on silicon substrates. In particular, we investigate losses introduced by Nb/Al interfaces in the center conductor, which is important for experiments where Al based Josephson junctions are integrated into Nb based circuits. We find that these interfaces can be a strong source for two-level state (TLS) losses, when the interfaces are not positioned at current nodes of the resonator. In addition to TLS losses, for resonators including Al, quasiparticle losses become relevant above 200 mK. Finally, we investigate how losses generated by eddy currents in conductive material on the backside of the substrate can be minimized by using thick enough substrates or metals with high conductivity on the substrate backside.
Antiferromagnetic and superconducting gaps and their interrelation in high-Tc cuprates

International Nuclear Information System (INIS)

Arrigoni, E.; Zacher, M.G.; Eckl, T.; Hanke, W.

2003-01-01

We propose a phenomenological model, comprising a microscopic SO(5) model plus the on-site Hubbard interaction U (projected SO(5) model) to understand the interrelation between the d-wave-gap modulation observed by recent angle-resolved photoemission experiments in the insulating antiferromagnet Ca 2 CuO 2 Cl 2 and the d-wave gap of high-T c superconducting materials. The on-site interaction U is important in order to produce a Mott gap of the correct order of magnitude, which would be absent in an exact SO(5) theory. The projected SO(5)-model explains the gap characteristics, namely both the symmetry and the different order of magnitude of the gap modulations between the AF and the SCc phases. Furthermore, it is shown that the projected SO(5) theory can provide an explanation for a recent observation [E. Pavarini et al., Phys. Rev. Lett. 87, 47003 (2001)], i. e. that the maximum T c observed in a large variety of high-T c cuprates scales with the next-nearest-neighbor hopping matrix element t'. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

Niobium thin film deposition studies on copper surfaces for superconducting radio frequency cavity applications

Energy Technology Data Exchange (ETDEWEB)

W. M. Roach, D. B. Beringer, J. R. Skuza, W. A. Oliver, C. Clavero, C. E. Reece, R. A. Lukaszew

2012-06-01

Thin film coatings have the potential to increase both the thermal efficiency and accelerating gradient in superconducting radio frequency accelerator cavities. However, before this potential can be realized, systematic studies on structure-property correlations in these thin films need to be carried out since the reduced geometry, combined with specific growth parameters, can modify the physical properties of the materials when compared to their bulk form. Here, we present our systematic studies of Nb thin films deposited onto Cu surfaces to clarify possible reasons for the limited success that this process exhibited in previous attempts. We compare these films with Nb grown on other surfaces. In particular, we study the crystal structure and surface morphology and their effect on superconducting properties, such as critical temperature and lower critical field. We found that higher deposition temperature leads to a sharper critical temperature transition, but also to increased roughness indicating that there are competing mechanisms that must be considered for further optimization.
Niobium thin film deposition studies on copper surfaces for superconducting radio frequency cavity applications

Directory of Open Access Journals (Sweden)

W. M. Roach

2012-06-01

Full Text Available Thin film coatings have the potential to increase both the thermal efficiency and accelerating gradient in superconducting radio frequency accelerator cavities. However, before this potential can be realized, systematic studies on structure-property correlations in these thin films need to be carried out since the reduced geometry, combined with specific growth parameters, can modify the physical properties of the materials when compared to their bulk form. Here, we present our systematic studies of Nb thin films deposited onto Cu surfaces to clarify possible reasons for the limited success that this process exhibited in previous attempts. We compare these films with Nb grown on other surfaces. In particular, we study the crystal structure and surface morphology and their effect on superconducting properties, such as critical temperature and lower critical field. We found that higher deposition temperature leads to a sharper critical temperature transition, but also to increased roughness indicating that there are competing mechanisms that must be considered for further optimization.
Niobium thin film deposition studies on copper surfaces for superconducting radio frequency cavity applications

International Nuclear Information System (INIS)

Roach, W.M.; Beringer, D.B.; Skuza, J.R.; Oliver, W.A.; Clavero, C.; Reece, C.E.; Lukaszew, R.A.

2012-01-01

Thin film coatings have the potential to increase both the thermal efficiency and accelerating gradient in superconducting radio frequency accelerator cavities. However, before this potential can be realized, systematic studies on structure-property correlations in these thin films need to be carried out since the reduced geometry, combined with specific growth parameters, can modify the physical properties of the materials when compared to their bulk form. Here, we present our systematic studies of Nb thin films deposited onto Cu surfaces to clarify possible reasons for the limited success that this process exhibited in previous attempts. We compare these films with Nb grown on other surfaces. In particular, we study the crystal structure and surface morphology and their effect on superconducting properties, such as critical temperature and lower critical field. We found that higher deposition temperature leads to a sharper critical temperature transition, but also to increased roughness indicating that there are competing mechanisms that must be considered for further optimization.
Model of vortex dynamics in superconducting films in two-coil measurements of the coherence length

Science.gov (United States)

Lemberger, Thomas; Loh, Yen Lee

In two-coil measurements on superconducting films, a magnetic field from a small coil is applied to the center of the film. When the amplitude of the ac field is increased, the film undergoes a transition from the ``Meissner'' state to a state with vortices and antivortices. Ultimately, the vortex density matches the applied magnetic field and field screening is negligible. Experimentally, the field at the transition is related to the superconducting coherence length, although a full theory of the relationship is lacking. We show that the mutual inductance between drive and pickup coils, on opposite sides of the film, as a function of ac field amplitude is well-described by a phenomenological model in which vortices and antivortices appear together in the film at the radius where the induced supercurrent is strongest, and then they move through a landscape of moderately strong vortex pinning sites. Work at OSU supported by DOE-Basic Energy Sciences through Grant No. FG02-08ER46533.
Enhanced pinning in superconducting thin films with graded pinning landscapes

Science.gov (United States)

Motta, M.; Colauto, F.; Ortiz, W. A.; Fritzsche, J.; Cuppens, J.; Gillijns, W.; Moshchalkov, V. V.; Johansen, T. H.; Sanchez, A.; Silhanek, A. V.

2013-05-01

A graded distribution of antidots in superconducting a-Mo79Ge21 thin films has been investigated by magnetization and magneto-optical imaging measurements. The pinning landscape has maximum density at the sample border, decreasing linearly towards the center. Its overall performance is noticeably superior than that for a sample with uniformly distributed antidots: For high temperatures and low fields, the critical current is enhanced, whereas the region of thermomagnetic instabilities in the field-temperature diagram is significantly suppressed. These findings confirm the relevance of graded landscapes on the enhancement of pinning efficiency, as recently predicted by Misko and Nori [Phys. Rev. B 85, 184506 (2012)].
Niobium Nitride Thin Films and Multilayers for Superconducting Radio Frequency Cavities

Science.gov (United States)

Roach, William; Beringer, Douglas; Li, Zhaozhu; Clavero, Cesar; Lukaszew, Rosa

2013-03-01

Niobium nitride in thin film form has been considered for a number of applications including multi-layered coatings onto superconducting radio frequency cavities which have been proposed to overcome the fundamental accelerating gradient limit of ~50 MV/m in niobium based accelerators. In order to fulfill the latter application, the selected superconductor's thermodynamic critical field, HC, must be larger than that of niobium and separated from the Nb surface by an insulating layer in order to shield the Nb cavity from field penetration and thus allow higher field gradients. Thus, for the successful implementation of such multilayered stack it is important to consider not just the materials inherent properties but also how these properties may be affected in thin film geometry and also by the specific deposition techniques used. Here, we show the results of our correlated study of structure and superconducting properties in niobium nitride thin films and discuss the shielding exhibited in NbN/MgO/Nb multilayer samples beyond the lower critical field of Nb for the first time. This work was funded by the Defense Threat Reduction Agency (HDTRA-10-1-0072).
Superconducting properties of In-Ge mixture films

International Nuclear Information System (INIS)

Gerber, A.; Deutscher, G.

1987-01-01

We report on measurements of the perpendicular H/sub c//sub perpendicular/ and parallel H/sub c//sub X/ upper critical fields of superconducting In-Ge mixture films in a wide range of In concentrations. The resistivities of the samples varied from about 10 μΩX, corresponding to high In concentration, up to about 1300 μΩ cm, corresponding to an In concentration close to the percolation threshold of the system. The critical temperatures of the samples in a zero external field have also been studied. For high metal concentrations the results have been analyzed and found to fit the predictions of the dirty limit for type-II superconductors. Near the threshold, however, where the normal-state resistivity goes to infinity, the critical fields saturate to a finite value. This result is in accordance with the prediction of percolation theory in the anomalous diffusion regime. As the threshold is approached the anisotropy ratio decreases to a constant value of 1.2 from its homogeneous type-II limit 1.69
Nanolayers with advanced properties for superconducting nanoelectronics

International Nuclear Information System (INIS)

Prepelita, A.; Zdravkov, V.; Morari, R.; Socrovisciuc, A.; Antropov, E.; Sidorenko, A.

2011-01-01

Full text: Elaborated advanced technology for superconducting spintronics - technological process, based on magnetron sputtering of the metallic films with non-metallic protective layers, yields significant improvement in superconducting properties of thin Nb films and Nb/CuNi nanostructures in comparison with common methods of films deposition. The developed advanced technological process is patented (Patent RM number 175 from 31.03.2010). First experimental observation of the double re-entrant superconductivity in superconductor/ ferromagnetic nanostructures (Nb/Cu 41 Ni 59 bilayers) in dependence on the thickness of the ferromagnetic layer (Published in : A.S. Sidorenko, V.I. Zdravkov, J. Kehrle, R.Morari, E.Antropov, G. Obermeier, S. Gsell, M. Schreck, C. Muller, V.V. Ryazanov, S. Horn, R. Tidecks, L.R. Tagirov. Extinction and recovery of superconductivity by interference in superconductor/ferromagnet bilayers. In: Nanoscale Phenomena . Fundamentals and Applications,Ed. by H.Hahn, A.Sidorenko, I.Tiginyanu, Springer, 2009 p.1-10. Perspectives of applications: design of a new generation of superconducting spintronic devices - high frequency operating superconducting spin-switch for telecommunication and computers. (author)
Superconducting quantum electronics

International Nuclear Information System (INIS)

Kose, V.

1989-01-01

This book reviews recent accomplishments, presents new results and discusses possible future developments of superconducting quantum electronics and high T c superconductivity. The three main parts of the book deal with fundamentals, sensitive detectors, and precision metrology. New results reported include: correct equivalent circuits modelling superconducting electronic devices; exact solution of the Mattis-Bardeen equations describing various experiments for thin films; complete theoretical description and experimental results for a new broad band spectrum analyzer; a new Josephson junction potentiometer allowing tracing of unknown voltage ratios back to well-known frequency ratios; and fast superconducting SQUID shift registers enabling the production of calculable noise power spectra in the microwave region
Magnetic force acting on a magnetic dipole over a superconducting thin film

International Nuclear Information System (INIS)

Wei, J.C.; Chen, J.L.; Horng, L.; Yang, T.J.

1996-01-01

The magnetostatic interaction energy and corresponding magnetic force acting on a magnetic point dipole placed above a type-II thin superconducting film in the mixed state with a single vortex are calculated using electromagnetics coupled with the London theory of superconductivity. If a vortex is trapped by a circular defect of radius b 1, where a is the separation between the dipole and the thin film, the only difference between two results is in the cutoff length, i.e., in the case of a circular defect the only difference in the critical position calculation is the cutoff at radius b rather than at coherence length ξ. The pinning force of a single vortex by a circular defect is also calculated. Further, we investigate the conditions of the vortex creation for various cases (including the first, second, and third vortices) for a free of pinning center in the examining region. It is found that the creation of a new single vortex in the thin film causes an abrupt change in vertical levitation force: the force changed discontinuously. copyright 1996 The American Physical Society
Modern high-temperature superconductivity

International Nuclear Information System (INIS)

Ching Wu Chu

1988-01-01

Ever since the discovery of superconductivity in 1911, its unusual scientific challenge and great technological potential have been recognized. For the past three-quarters of a century, superconductivity has done well on the science front. This is because sueprconductivity is interesting not only just in its own right but also in its ability to act as a probe to many exciting nonsuperconducting phenomena. For instance, it has continued to provide bases for vigorous activities in condensed matter science. Among the more recent examples are heavy-fermion systems and organic superconductors. During this same period of time, superconductivity has also performed admirably in the applied area. Many ideas have been conceived and tested, making use of the unique characteristics of superconductivity - zero resistivity, quantum interference phenomena, and the Meissner effect. In fact, it was not until late January 1987 that it became possible to achieve superconductivity with the mere use of liquid nitrogen - which is plentiful, cheap, efficient, and easy to handle - following the discovery of supercondictivity above 90 K in Y-Ba-Cu-O, the first genuine quaternary superconductor. Superconductivity above 90 K poses scientific and technological challenges not previously encountered: no existing theories can adequately describe superconductivity above 40 K and no known techniques can economically process the materials for full-scale applications. In this paper, therefore, the author recalls a few events leading to the discovery of the new class of quaternary compounds with a superconducting transition temperature T c in the 90 K range, describes the current experimental status of high-temperature superconductivity and, finally, discusses the prospect of very-high-temperature superconductivity, i.e., with a T c substantially higher than 100 K. 97 refs., 7 figs
Magnetic levitation and superconductivity

International Nuclear Information System (INIS)

Albrecht, C.

1989-01-01

The paper explains the impressive advances made in the development of superconducting magnets, in cryogenic engineering, and in the development of drive and vehicle concepts in Japan in the period following termination of West German development work for the electrodynamical system (MLU 001, MLU 002). The potentials engineering due to the development of high-Tc superconductors are discussed. (orig./MM) [de
Growth orientation and superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} films prepared by the low-fluorine sol-gel process

Energy Technology Data Exchange (ETDEWEB)

Lei Li; Zhao Gaoyang; Xu Hui; Zhao Juanjuan, E-mail: leili813@gmail.co [School of Materials Science and Engineering, Xi' an University of Technology, Xi' an 710048 (China)

2010-08-15

YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films were deposited on (100)-oriented LaAlO{sub 3} (LAO) single crystal substrates by the dip-coating process using low-fluorine solution. Their microstructures were characterized with the aid of X-ray diffractometry, scanning electron microscopy and high-resolution transmission electron microscopy. Their superconducting properties were measured by the standard four-probe method. The experiment results show that the film obtained under high enough humidity conditions exhibits better c-axis texture and superconducting properties than the film under a relatively low humidity conditions. Based on the classical nucleation and chemical reaction thermodynamics theory, the underlying crystalline and growth mechanisms of YBCO films under certain humidity conditions are explained in combination with our experimental results. It is suggested that the unreacted intermediate phases such as BaF{sub 2} and CuO aggregated in the YBCO grain boundary will cause lattice distortion in the YBCO matrix and further induce the formation of a-axis oriented YBCO grains as crystallization proceeds. Therefore, it is believed that the relative content of water vapor within the heat-treatment atmosphere plays quite an important role in the preparation of c-axis oriented YBCO film with good superconducting properties. (semiconductor materials)
Electron scattering rate in epitaxial YBa2Cu3O7 superconducting films

Science.gov (United States)

Flik, M. I.; Zhang, Z. M.; Goodson, K. E.; Siegal, M. P.; Phillips, Julia M.

1992-09-01

This work determines the electron scattering rate in the a-b plane of epitaxial YBa2Cu3O7 films using two techniques. Infrared spectroscopy yields the scattering rate at temperatures of 10, 78, and 300 K by fitting reflectance data using thin-film optics and a model for the free-carrier conductivity. The scattering rate is also obtained using kinetic theory and an extrapolation of normal-state electrical resistivity data to superconducting temperatures based on the Bloch theory for the phonon-limited electrical resistivity of metals. The scattering rates determined using both techniques are in agreement and show that the electron mean free path in the a-b plane of YBa2Cu3O7 superconducting films is three to four times the coherence length. Hence YBa2Cu3O7 is pure but not in the extreme pure limit. An average defect interaction range of 4 nm is obtained using the defect density resulting from flux-pinning considerations.
Superconductivity effects near metal-insulator transition in granular idnium films

International Nuclear Information System (INIS)

Belevtsev, B.I.; Komnik, Yu.F.; Fomin, A.V.

1986-01-01

The influence of granules superconductivity on the electric properties of granular indium films is investigated under the conditions of partial or full granular localization of electrons. At temperatures below 5 K a minimum of electric resistance and negative magnetoresistance are revealed which are attributed to the competition of hopping conductivity and Josephson intergranular tunneling of electrons
Ion-channeling study of anomalous atomic displacements at the superconducting transition in high-Tc materials

International Nuclear Information System (INIS)

Rehn, L.E.; Sharma, R.P.; Baldo, P.M.

1991-01-01

Ion channeling along the [001] direction in high-quality single crystals of (Y/Er)Ba 2 Cu 3 O 7-x revealed an abrupt change in displace-ments in the a-b plane of the Cu and O atoms at the superconducting transition, T c ; normal 'Debye-like' vibrations were found for the Y/Er and Ba atoms. The anomalous change in Cu-O displacements was found to shift directly with stoichiometry-induced changes in T c , implying a direct link between the observed phonon anomaly and the superconducting transition. Recent measurements of ion-channeling along the [001] axis in (Bi 1.7 Pb 0.3 )Sr 2 Ca 1 Cu 2 O x single-crystals revealed a similar change at T c , suggesting that this phonon anomaly is a general feature of high-T c superconductivity. In order to identify more specifically the crystallographic directions and displacement amplitudes associated with the anomalous phonon behavior, axial channeling scans using RBS, as well as characteristic x-ray production, were taken at several temperatures between 30 and 300K along the [301] and [331] directions of YBa 2 Cu 3 O 7-x single crystals. Twins present in the specimens, and the existing static atomic displacements present along these directions, caused the channeling to be poorer along these axes compared to the (001) direction. Also, a much stronger dependence of the minimum yield on depth was observed. However, since only one twin variant generally dominated over sufficiently wide areas of the specimens, reasonably good (approx 10 percent) minimum yields could be obtained along the appropriate [331] axis, and detwinned crystals produced good results along [301]. (author). 27 refs.; 5 figs
Observation of high Tc one dimensional superconductivity in 4 angstrom carbon nanotube arrays

KAUST Repository

Zhang, Bing; Liu, Yang; Chen, Qihong; Lai, Zhiping; Sheng, Ping

2017-01-01

The only known approach to fabricate large, uniform arrays of 4-Å single wall carbon nanotubes (SWNTs) is by using zeolite crystals as the template, in which the nanotubes are formed by chemical vapor deposition inside the linear channels of the AlPO-5 (AFI for short) zeolite. However, up to now the pore filling factor has been very low, as evidenced by the weight percentage of carbon in thermal gravimetric analysis (TGA) measurements. In this work, we show that by using a new, micro-platelet AFI crystals as the template, combined with the use of a new CVD process, we can increase the TGA result to 22.5wt%, which translates to a pore filling factor of 91%. We have observed one dimensional (1D) superconductivity in such samples. The temperature dependence of resistance shows a smooth decreasing trend below 60 K, and the differential resistance displays a gap that disappears above the 1D superconducting initiation temperature. The observed behaviour is shown to agree very well with the theoretical predictions of 1D superconductivity.
Observation of high Tc one dimensional superconductivity in 4 angstrom carbon nanotube arrays

KAUST Repository

Zhang, Bing

2017-02-14

The only known approach to fabricate large, uniform arrays of 4-Å single wall carbon nanotubes (SWNTs) is by using zeolite crystals as the template, in which the nanotubes are formed by chemical vapor deposition inside the linear channels of the AlPO-5 (AFI for short) zeolite. However, up to now the pore filling factor has been very low, as evidenced by the weight percentage of carbon in thermal gravimetric analysis (TGA) measurements. In this work, we show that by using a new, micro-platelet AFI crystals as the template, combined with the use of a new CVD process, we can increase the TGA result to 22.5wt%, which translates to a pore filling factor of 91%. We have observed one dimensional (1D) superconductivity in such samples. The temperature dependence of resistance shows a smooth decreasing trend below 60 K, and the differential resistance displays a gap that disappears above the 1D superconducting initiation temperature. The observed behaviour is shown to agree very well with the theoretical predictions of 1D superconductivity.
The growth of large-area superconducting YBa2Cu3O7-x thin films by pulsed laser ablation

International Nuclear Information System (INIS)

Lai, H.C.; Chang, C.M.; Lin, R.J.; Liu, R.S.

1996-01-01

In-situ growth of 2-in. diameter superconducting YBa 2 Cu 3 O 7-x (YBCO) thin films using an excimer KrF pulsed laser has been studied. Films with critical transition temperature (T c,0 ) of 89±1 K and critical current density (J c,77K ) in excess of 1 x 10 6 A cm -2 have been prepared routinely. Uniformity in film thickness of below ±15% and film composition of ±5% have been measured. The effects of gas nozzle geometry and target evolution during ablation on the superconducting properties and surface morphology of YBCO thin films have also been investigated. (orig.)
High-performance magnetic field sensor based on superconducting quantum interference filters

Science.gov (United States)

Caputo, P.; Oppenländer, J.; Häussler, Ch.; Tomes, J.; Friesch, A.; Träuble, T.; Schopohl, N.

2004-08-01

We have developed an absolute magnetic field sensor using a superconducting quantum interference filter (SQIF) made of high-Tc grain-boundary Josephson junctions. The device shows the typical magnetic-field-dependent voltage response V(B ), which is a sharp deltalike dip in the vicinity of zero-magnetic field. When the SQIF is cooled with magnetic shield, and then the shield is removed, the presence of the ambient magnetic field induces a shift of the dip position from B0≈0 to a value B ≈B1, which is about the average value of the Earth's magnetic field, at our latitude. When the SQIF is cooled in the ambient field without shielding, the dip is first found at B ≈B1, and the further shielding of the SQIF results in a shift of the dip towards B0≈0. The low hysteresis observed in the sequence of experiments (less than 5% of B1) makes SQIFs suitable for high precision measurements of the absolute magnetic field. The experimental results are discussed in view of potential applications of high-Tc SQIFs in magnetometry.

Measurement of the magnetic penetration depth in p-doped superconducting diamond films

Energy Technology Data Exchange (ETDEWEB)

Fuchs, Lorenz; Brunner, Markus C.P.; Schneider, Ina; Kronfeldner, Klaus [University of Regensburg (Germany); Bousquet, Jessica; Bustarret, Etienne; Strunk, Christoph [Institut Neel, Grenoble (France)

2016-07-01

Boron-doped diamond becomes superconducting once a critical doping concentration of 4.5 x 10{sup 20} cm{sup -3} is reached. Mutual inductance measurements with a two-coil setup have been performed to determine the magnetic penetration depth λ(T), which is a measure for the superfluid stiffnes θ ∝ 1/λ{sup 2}(T). Two superconducting p-doped diamond films with thicknesses of 145 nm and 345 nm were investigated. At low temperatures these values agree reasonably with the values expected within BCS-theory using T{sub c}, carrier density and mean free path determined from electric transport measurements. Magnetic penetration depths of 3.7 μm for the thinner and 2.6 μm for the thicker film have been found. λ decreases and accordingly θ increases with increasing film thickness. On the other hand, the superfluid stiffness drops by a factor of 2 or even more at T{sub c}/2, i.e., much faster than expected from BCS-theory, but remains finite between T{sub c}/2 < T < T{sub c}. At present it is unclear, whether this behavior results from the proliferation of phase fluctuations already far below T{sub c} or from a spatial inhomogeneity of the films.
Enhanced superconductivity and superconductor to insulator transition in nano-crystalline molybdenum thin films

Energy Technology Data Exchange (ETDEWEB)

Sharma, Shilpam; Amaladass, E.P. [Condensed Matter Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Sharma, Neha [Surface & Nanoscience Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Harimohan, V. [Condensed Matter Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Amirthapandian, S. [Materials Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Mani, Awadhesh, E-mail: mani@igcar.gov.in [Condensed Matter Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

2017-06-01

Disorder driven superconductor to insulator transition via intermediate metallic regime is reported in nano-crystalline thin films of molybdenum. The nano-structured thin films have been deposited at room temperature using DC magnetron sputtering at different argon pressures. The grain size has been tuned using deposition pressure as the sole control parameter. A variation of particle sizes, room temperature resistivity and superconducting transition has been studied as a function of deposition pressure. The nano-crystalline molybdenum thin films are found to have large carrier concentration but very low mobility and electronic mean free path. Hall and conductivity measurements have been used to understand the effect of disorder on the carrier density and mobilities. Ioffe-Regel parameter is shown to correlate with the continuous metal-insulator transition in our samples. - Highlights: • Thin films of molybdenum using DC sputtering have been deposited on glass. • Argon background pressure during sputtering was used to tune the crystallite sizes of films. • Correlation in deposition pressure, disorder and particle sizes has been observed. • Disorder tuned superconductor to insulator transition along with an intermediate metallic phase has been observed. • Enhancement of superconducting transition temperature and a dome shaped T{sub C} vs. deposition pressure phase diagram has been observed.
Superconducting Technology Program: Sandia 1993 annual report

International Nuclear Information System (INIS)

Roth, E.P.

1994-05-01

Sandia's STP program is a four-part high-temperature superconductor (HTS) research and development program consisting of efforts in powder synthesis and process development, thallium-based HTS film development, wire and tape fabrication, and HTS motor design. The objective of this work is to develop high-temperature superconducting conductors (wire and tape) capable of meeting requirements for high-power electrical devices of interest to industry. The four research efforts currently underway are: (1) process research on the material synthesis of high-temperature superconductors; (2) investigation of the synthesis and processing of thallium-based high-temperature superconducting thick films; (3) process development and characterization of high-temperature superconducting wire and tape, and (4) cryogenic design of a high-temperature superconducting motor. This report outlines the research that has been performed during FY93 in each of these four areas. A brief background of each project is included to provide historical context and perspective. Major areas of research are described, although no attempt has been made to exhaustively include all work performed in each of these areas
Transport in reversibly laser-modified YBa2Cu3O/sub 7-//sub x/ superconducting thin films

International Nuclear Information System (INIS)

Krchnavek, R.R.; Chan, S.; Rogers, C.T.; De Rosa, F.; Kelly, M.K.; Miceli, P.F.; Allen, S.J.

1989-01-01

A focused argon ion laser beam in a controlled ambient is used to modify the transport properties of superconducting YBa 2 Cu 3 O/sub 7-//sub x/ thin films. The laser-modified region shows a sharp transition temperature (T/sub c/≅76 K) that is reduced from the unmodified regions of the film (T/sub c/≅87 K). In situ monitoring of the room-temperature electrical resistance is used to control the laser processing and prevent formation of the semiconducting phase. The original properties of the superconducting film can be recovered by plasma oxidation indicating that the laser-induced phase is oxygen deficient
Structural and superconducting characteristics of YBa2Cu3O7 films grown by fluorine-free metal-organic deposition route

DEFF Research Database (Denmark)

Zhao, Yue; Chu, Jingyuan; Qureishy, Thomas

2018-01-01

Microstructure and superconducting performance of YBa2Cu3O7 (YBCO) films deposited on LaAlO3 single crystal (LAO) substrates by a fluorine-free metal-organic deposition (FF-MOD) technique, have been studied by means of X-ray reciprocal space mapping (RSM), cross-sectional transmission electron mi...... external magnetic field at 77 K. This work offers an in-depth insight into the correlation between the microstructure and superconductivity in the MOD YBCO films.......Microstructure and superconducting performance of YBa2Cu3O7 (YBCO) films deposited on LaAlO3 single crystal (LAO) substrates by a fluorine-free metal-organic deposition (FF-MOD) technique, have been studied by means of X-ray reciprocal space mapping (RSM), cross-sectional transmission electron....... It is suggested that associated partial dislocations formed at the boundary between the stacking faults and YBCO matrix act as strong linear (or dot) pinning centers. These structural characteristics are well in line with the better superconducting performance of the low fluorine-MOD film, in particular under...
Towards a Cryogen-Free MgB2-Based Superconducting Radio Frequency Accelerating Cavities

Science.gov (United States)

Nassiri, Alireza

Studies on the application of Magnesium diboride (MgB2) superconducting films have shown promise for use with the radio-frequency (SRF) accelerating cavities. MgB2\\ coating is a potential candidate to replace bulk niobium (Nb) SRF cavities. The ultimate goal of our research is to demonstrate MgB2 coating on copper cavities to allow operation at about 20 K or so as a result of the high transition temperature (Tc) of MgB2 and taking advantage of the excellent thermal conductivity of copper. Here, we will report on our recent experimental results of applying hybrid physical-chemical vapor deposition (HPCVD) to grow MgB2 films on 2-inch diameter copper discs as well as on a 2.8 GHz resonator cavity *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06H11357.
Spectroscopic Imaging Scanning Tunneling Microscopy Studies of Electronic Structure in the Superconducting and Pseudogap Phases of Cuprate High-Tc Superconductors

Science.gov (United States)

Fujita, Kazuhiro; Schmidt, Andrew R.; Kim, Eun-Ah; Lawler, Michael J.; Lee, Dung Hai; Davis, J. C.; Eisaki, Hiroshi; Uchida, Shin-ichi

2012-01-01

phase diagram and the mechanism of high-Tc superconductivity, represents one of a key challenges for cuprate studies.
A study on the superconducting properties of YBa2Cu9-xNbxOy thin films

International Nuclear Information System (INIS)

Srinivas, S.; Bhatnagar, A.K.; Pinto, R.

1994-01-01

Effect of niobium substitution at the copper site in YBa 2 Cu 9 O 7-x was studied in thin film form. The films were deposited by laser ablation technique using the targets of the YBa 2 Cu 3-x Nb x O y where x = 0.0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8 and 1.0 under identical deposition conditions on SrTiO 9 substrates. Films were characterized by XRD, resistivity, I-V and J c measurements. Films made from x = 0.025 and 0.05 concentrations of Nb substituted targets showed relatively improved superconducting properties compared to that of undoped films. The best 7 realized for x = 0.025 Nb concentration was 1.8 x 10 σ A/cm 2 and for 0.05 Nb concentration it was 3.2x10 σ A/cm 2 at 77K. However, degradation of the superconducting properties, with the increase of x ≥ 0.1 Nb concentration and drastic suppression and complete loss of superconductivity was noticed for x ≥ 0.4. The growth of impurity phase YBa 2 NbO 6 for x = 0.1 and above of Nb concentration was noticed from XRD patterns. However, the site occupancy of Nb could not be confirmed from these studies
Analysis of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applications

Science.gov (United States)

Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.

1996-01-01

The prospects of a YBa2Cu3O7(delta)(YBCO) hot-electron bolometer (HEB) mixer for a THz heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate.
Related electrical, superconducting and structural characteristics of low temperature indium films

International Nuclear Information System (INIS)

Belevtsev, B.I.; Pilipenko, V.V.; Yatsuk, L.Ya.

1981-01-01

Reported are results of a complex study of electrical, superconducting and structural properties of indium films vacuum evaporated onto a liquid helium-cooled substrate. Structural electron diffraction investigations gave a better insight into the general features of the annealing during the warming-up of cold-deposited films. It is found that the annealing of indium films to about 80 to 100 K entails an irreversible growth of interplanar separations due to decreasing inhomogeneous microstresses. As the films are warmed from 100 to 300 K, the principal annealing processes are determined by crystallite growth and development of dominating orientation. The changes in the residual resistance and in Tsub(c) with warming the cold-deported films are explained on the base of structural data obtained. In particular, a direct relationship is revealed between the crystallite size and Tsub(c) [ru
Imaging of current distributions in superconducting thin film structures

International Nuclear Information System (INIS)

Doenitz, D.

2006-01-01

Local analysis plays an important role in many fields of scientific research. However, imaging methods are not very common in the investigation of superconductors. For more than 20 years, Low Temperature Scanning Electron Microscopy (LTSEM) has been successfully used at the University of Tuebingen for studying of condensed matter phenomena, especially of superconductivity. In this thesis LTSEM was used for imaging current distributions in different superconducting thin film structures: - Imaging of current distributions in Josephson junctions with ferromagnetic interlayer, also known as SIFS junctions, showed inhomogeneous current transport over the junctions which directly led to an improvement in the fabrication process. An investigation of improved samples showed a very homogeneous current distribution without any trace of magnetic domains. Either such domains were not present or too small for imaging with the LTSEM. - An investigation of Nb/YBCO zigzag Josephson junctions yielded important information on signal formation in the LTSEM both for Josephson junctions in the short and in the long limit. Using a reference junction our signal formation model could be verified, thus confirming earlier results on short zigzag junctions. These results, which could be reproduced in this work, support the theory of d-wave symmetry in the superconducting order parameter of YBCO. Furthermore, investigations of the quasiparticle tunneling in the zigzag junctions showed the existence of Andreev bound states, which is another indication of the d-wave symmetry in YBCO. - The LTSEM study of Hot Electron Bolometers (HEB) allowed the first successful imaging of a stable 'Hot Spot', a self-heating region in HEB structures. Moreover, the electron beam was used to induce an - otherwise unstable - hot spot. Both investigations yielded information on the homogeneity of the samples. - An entirely new method of imaging the current distribution in superconducting interference devices
Hall effect measurements of high-quality M n3CuN thin films and the electronic structure

Science.gov (United States)

Matsumoto, Toshiki; Hatano, Takafumi; Urata, Takahiro; Iida, Kazumasa; Takenaka, Koshi; Ikuta, Hiroshi

2017-11-01

The physical properties of M n3CuN were studied using thin films. We found that an annealing process was very effective to improve the film quality, the key of which was the use of Ti that prevented the formation of oxide impurities. Using these high-quality thin films, we found strong strain dependence for the ferromagnetic transition temperature (TC) and a sign change of the Hall coefficient at TC. The analysis of Hall coefficient data revealed a sizable decrease of hole concentration and a large increase of electron mobility below TC, which is discussed in relation to the electronic structure of this material.
The war of the cold: an history of the superconductivity

International Nuclear Information System (INIS)

Matricon, J.; Waysand, G.

1994-01-01

The evolution of superconductivity is described from a scientific, and social points of view. The evolution of researches and realizations towards the absolute zero temperature leading to the discovery of superconductivity by Gilles Holst in 1991, is followed by the theoretical modelization of the superconductivity phenomena leading to the Ginzburg and Landau theory in 1950 and to the Bardeen, Cooper and Schrieffer theory in 1957. Then researches on materials that lead to high-tc superconductors are presented with some applications. (A.B.). refs., figs,. tabs
High-Tc Superconductors Based on FeAs Compounds

CERN Document Server

Izyumov, Yuri

2010-01-01

Physical properties and models of electronic structure are analyzed for a new class of high-TC superconductors which belong to iron-based layered compounds. Despite their variable chemical composition and differences in the crystal structure, these compounds possess similar physical characteristics, due to electron carriers in the FeAs layers and the interaction of these carriers with fluctuations of the magnetic order. A tremendous interest towards these materials is explained by the prospects of their practical use. In this monograph, a full picture of the formation of physical properties of these materials, in the context of existing theory models and electron structure studies, is given. The book is aimed at a broad circle of readers: physicists who study electronic properties of the FeAs compounds, chemists who synthesize them and specialists in the field of electronic structure calculations in solids. It is helpful not only to researchers active in the fields of superconductivity and magnetism, but also...
Superconductivity in volumetric and film ceramics Bi-Sr-Ca-Cu-O

International Nuclear Information System (INIS)

Sukhanov, A.A.; Ozmanyan, Kh.R.; Sandomirskij, B.B.

1988-01-01

A superconducting transition with T c0 =82-95 K and T c (R=0)=82-72 K was observed in volumetric and film Bi(Sr 1-x Ca x ) 2 Cu 3 O y samples obtained by solid-phase reaction. Temperature dependences of resistance critical current and magnetic susceptibility are measured
Midwest Superconductivity Consortium: 1994 Progress report

Energy Technology Data Exchange (ETDEWEB)

1995-01-01

The mission of the Midwest Superconductivity Consortium, MISCON, is to advance the science and understanding of high {Tc} superconductivity. During the past year, 27 projects produced over 123 talks and 139 publications. Group activities and interactions involved 2 MISCON group meetings (held in August and January); with the second MISCON Workshop held in August; 13 external speakers; 79 collaborations (with universities, industry, Federal laboratories, and foreign research centers); and 48 exchanges of samples and/or measurements. Research achievements this past year focused on understanding the effects of processing phenomena on structure-property interrelationships and the fundamental nature of transport properties in high-temperature superconductors.
Debye frequency and interplay of superconductivity and antiferromagnetism in high Tc superconductors

International Nuclear Information System (INIS)

Panigrahy, N.N.; Mahapatra, D.; Panda, B.N.; Rout, G.C.

2006-01-01

The interplay between superconductivity (SC) and antiferromagnetism (AFM) is studied in strongly correlated systems: R 2-x M x CuO 4 (R = Nd, La, Pr. Gd; M = Sr, Ce) due to electron-phonon interaction, It is assumed that SC arises due to BCS pairing mechanism in presence of AFM in Cu lattices of Cu-O planes, Debye frequency ω D dependence of high temperature SC gap as well as staggered magnetic field at different temperatures are calculated analytically and solved self-consistently with respect to half-filled band situation for different model parameters (temperature parameter θ and hybridization parameter ν, λ 1 and λ 2 being the SC and AF coupling parameters, respectively). The SC gap and AFM gap are studied in their coexistence phase for different Debye frequencies. (author)
An investigation into texturing of high-Tc superconducting ceramics by creep-sintering

International Nuclear Information System (INIS)

Regnier, P.; Le Hazif, R.; Chaffron, L.

1989-01-01

The possibility of preparing highly textured samples of YBa 2 Cu 3 O 7-x high-Tc ceramics by creep-sintering under an uniaxial stress was investigated in detail. It is shown that the quality of the texture is sharply dependant on: the applied load, the temperature of the sintering dwell, the rate at which this dwell is reached, the exact instant at which the load is applied and the nature of the material in contact with the sample. It is also shown that further annealing without applied stress enhances the texture and considerably increases the grain size. Deformation, which was systematically recorded, occurs within a few minutes after the load is applied and exhibits a stress dependance typical of a viscous flow. Systematic examination by polarized light microscopy has indicated that the texture was homogeneous throughout the whole thickness of all the prepared samples. The resistivity versus temperature curves show that the transition is very sharp and well above 77 K
Analysis of a high-Tc hot-electron superconducting mixer for terahertz applications

International Nuclear Information System (INIS)

Karasik, B.S.; McGrath, W.R.; Gaidis, M.C.

1997-01-01

The prospects of a YBa 2 Cu 3 O 7-δ hot-electron bolometer mixer for a THz heterodyne receiver are discussed. The modeled device is a submicron bridge made from a 10-nm-thick film on a high thermal conductance substrate. The mixer performance expected for this device is analyzed in the framework of a two-temperature model which includes heating both of the electrons and the lattice. Also, the contribution of phonon diffusion from the film through the substrate and from the film to the normal metal contacts is evaluated. The intrinsic conversion efficiency and the noise temperature have been calculated as functions of the device size, local oscillator (LO) power, and ambient temperature. Assuming thermal fluctuations and Johnson noise to be the main sources of noise, a minimum single sideband mixer noise temperature of congruent 2000 K is predicted. For our modeled device the intrinsic conversion loss at an intermediate frequency of 2.5 GHz is less than 10 dB and the required LO power is ∼1 endash 10 μW. copyright 1997 American Institute of Physics
Collective-pinning properties of superconducting a-NbxGe and a-MoxSi films

International Nuclear Information System (INIS)

Woerdenweber, R.

1987-01-01

This thesis describes a study of superconducting flux pinning in amorphous NbGe and MoSi films of various compositions and thickness. Amorphous NbGe and MoSi alloys belong to the weak-coupling type-II superconductors in the extreme dirty limit. This feature enables to determine several important superconducting parameters from well-known theoretical expressions. It is also responsible for the weak pinning, which is necessary to observe the two-dimensional collective pinning properties according to the Larkin-Ovchinnikov theory. (Auth.)

Influence of reversible epitactical stress on the electronic properties of thin superconducting films

International Nuclear Information System (INIS)

Trommler, Sascha

2014-01-01

In this thesis new stress techniques are applied on thin superconducting (La,Sr) 2 CuO 4 and BaFe 1.8 Co 0.2 As 2 films. At one hand piezoelectric substrates are applied, which make a biaxial stress of the thin film deposed there possible, whereby the lattice parameters of the substrate are altered by an electric field. At the other hand on the base of flexible substrates by means of a bending experiment a uniaxial lattice deformation of thin film is realized.
Quasi-One-Dimensional Intermittent Flux Behavior in Superconducting Films

Directory of Open Access Journals (Sweden)

A. J. Qviller

2012-01-01

Full Text Available Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YBa_{2}Cu_{3}O_{7-δ} deposited on tilted substrates. Deposition of this material on such substrates creates parallel channels of easy flux penetration when a magnetic field is applied perpendicular to the film. As the applied field is gradually increased, magneto-optical imaging reveals that flux penetrates via numerous quasi-one-dimensional jumps. The distribution of flux avalanche sizes follows a power law, and data collapse is obtained by finite-size scaling, with the depth of the flux front used as crossover length. The intermittent behavior shows no threshold value in the applied field, in contrast to conventional flux jumping. The results strongly suggest that the quasi-one-dimensional flux jumps are of a different nature than the thermomagnetic dendritic (branching avalanches that are commonly found in superconducting films.
Vortex pinning in superconducting Nb thin films deposited on nanoporous alumina templates

DEFF Research Database (Denmark)

Vinckx, W.; Vanacken, J.; Moshchalkov, V.V.

2006-01-01

We present a study of magnetization and transport properties of superconducting Nb thin films deposited on nanoporous aluminium oxide templates. Periodic oscillations in the critical temperature vs. field, matching effects in fields up to 700 mT and strongly enhanced critical currents were observed...
High-Tc SQUID Application for Roll to Roll Metallic Contaminant Detector

International Nuclear Information System (INIS)

Tanaka, S.; Kitamura, Y.; Uchida, Y.; Hatsukade, Y.; Ohtani, T.; Suzuki, S.

2012-01-01

A sensitive eight-channel high-Tc Superconducting Interference Device (SQUID) detection system for magnetic contaminant in a lithium ion battery anode was developed. Finding ultra-small metallic foreign matter is an important issue for a manufacturer because metallic contaminants carry the risk of an internal short. When contamination occurs, the manufacturer of the product suffers a great loss from recalling the tainted product. Metallic particles with outer dimensions smaller than 100 microns cannot be detected using a conventional X-ray imaging system. Therefore, a highly sensitive detection system for small foreign matter is required. We have already developed a detection system based on a single-channel SQUID gradiometer and horizontal magnetization. For practical use, the detection width of the system should be increased to at least 65 mm by employing multiple sensors. In this paper, we present an 8-ch high-Tc SQUID roll-to-roll system for inspecting a lithium-ion battery anode with a width of 65 mm. A special microscopic type of a cryostat was developed upon which eight SQUID gradiometers were mounted. As a result, small iron particles of 35 microns on a real lithium-ion battery anode with a width of 70 mm were successfully detected. This system is practical for the detection of contaminants in a lithium ion battery anode sheet.
Resonance of Superconducting Microstrip Antenna with Aperture in the Ground Plane

Directory of Open Access Journals (Sweden)

S. Benkouda

2013-08-01

Full Text Available This paper presents a rigorous full-wave analysis of a high Tc superconducting rectangular microstrip antenna with a rectangular aperture in the ground plane. To include the effect of the superconductivity of the microstrip patch in the full-wave analysis, a complex surface impedance is considered. The proposed approach is validated by comparing the computed results with previously published data. Results showing the effect of the aperture on the resonance of the superconducting microstrip antenna are given.
Achieving a Collapsible, Strong, and Highly Thermally Conductive Film Based on Oriented Functionalized Boron Nitride Nanosheets and Cellulose Nanofiber.

Science.gov (United States)

Wu, Kai; Fang, Jinchao; Ma, Jinrui; Huang, Rui; Chai, Songgang; Chen, Feng; Fu, Qiang

2017-09-06

Boron nitride nanosheet (BNNS) films receive wide attention in both academia and industry because of their high thermal conductivity (TC) and good electrical insulation capability. However, the brittleness and low strength of the BNNS film largely limit its application. Herein, functionalized BNNSs (f-BNNSs) with a well-maintained in-plane crystalline structure were first prepared utilizing urea in the aqueous solution via ball-milling for the purpose of improving their stability in water and enhancing the interaction with the polymer matrix. Then, a biodegradable and highly thermally conductive film with an orderly oriented structure based on cellulose nanofibers (CNFs) and f-BNNSs was prepared just by simple vacuum-assisted filtration. The modification of the BNNS and the introduction of the CNF result in a better orientation of the f-BNNS, sufficient connection between f-BNNS themselves, and strong interaction between f-BNNS and CNF, which not only make the prepared composite film strong and tough but also possess higher in-plane TC. An increase of 70% in-plane TC, 63.2% tensile strength, and 77.8% elongation could be achieved for CNF/f-BNNS films, compared with that for CNF/BNNS films at the filler content of 70%. Although at such a high f-BNNS content, this composite film can be bended and folded. It is even more interesting to find that the in-plane TC could be greatly enhanced with the decrease of the thickness of the film, and a value of 30.25 W/m K can be achieved at the thickness of ∼30 μm for the film containing 70 wt % f-BNNS. We believe that this highly thermally conductive film with good strength and toughness could have potential applications in next-generation highly powerful and collapsible electronic devices.
Anomalous electron doping independent two-dimensional superconductivity

Science.gov (United States)

Zhou, Wei; Xing, Xiangzhuo; Zhao, Haijun; Feng, Jiajia; Pan, Yongqiang; Zhou, Nan; Zhang, Yufeng; Qian, Bin; Shi, Zhixiang

2017-07-01

Transition metal (Co and Ni) co-doping effects are investigated on an underdoped Ca0.94La0.06Fe2As2 compound. It is discovered that electron doping from substituting Fe with transition metal (TM = Co, Ni) can trigger high-{T}{{c}} superconductivity around 35 K, which emerges abruptly before the total suppression of the innate spin-density-wave/anti-ferromagnetism (SDW/AFM) state. Remarkably, the critical temperature for the high-{T}{{c}} superconductivity remains constant against a wide range of TM doping levels. And the net electron doping density dependence of the superconducting {T}{{c}} based on the rigid band model can be nicely scaled into a single curve for Co and Ni substitutions, in stark contrast to the case of Ba(Fe1-x TM x )2As2. This carrier density independent superconductivity and the unusual scaling behavior are presumably resulted from the interface superconductivity based on the similarity with the interface superconductivity in a La2-x Sr x CuO4-La2CuO4 bilayer. Evidence of the two-dimensional character of the superfluid by angle-resolved magneto-resistance measurements can further strengthen the interface nature of the high-{T}{{c}} superconductivity.
A universal order underlying the pseudogap regime of the underdoped high Tc cuprates

Science.gov (United States)

Harrison, Neil

2014-03-01

A major achievement in condensed matter physics in the last quarter century has been a step towards the understanding of the unconventional d-wave superconducting state in the copper-oxide materials. Surprisingly, the normal state out of which the superconducting state emerges remains a mystery at low charge carrier densities, i.e., in the underdoped regime. This regime is of particular interest because it is characterised by an unusual momentum dependent energy pseudogap in the excitation spectrum that has defied explanation and is key to a full understanding of the unconventional d-wave superconducting state. I will present new quantum oscillation experimental results within the pseudogap regime of the high Tc superconductors YBa2Cu3O6+x and YBa2Cu4O8 which now extend up to the optimally-doped regime. These data reveal the evolution of the Fermi surface approaching the putative quantum critical point under the superconducting dome. A comprehensive angle-resolved study of the Fermi surface enables us to unambiguously identify a specific form of order that accounts for the observed quantum oscillations as well as other spectroscopic, transport and thermodynamic probes within the pseudogap regime. The author would like to thank B. Ramshaw, S. Sebastian, F. Balakirev, C. Mielke, M. Altarawneh, P. Goddard, S. Sabok, B. Babrowski, D. Bonn, W. Hardy, R. Liang and G. Lonzarich. This work was supported by the DOE BES ``Science of 100 tesla'' project and by the NSF and Florida State.
Dimensionality Driven Enhancement of Ferromagnetic Superconductivity in URhGe

Science.gov (United States)

Braithwaite, Daniel; Aoki, Dai; Brison, Jean-Pascal; Flouquet, Jacques; Knebel, Georg; Nakamura, Ai; Pourret, Alexandre

2018-01-01

In most unconventional superconductors, like the high-Tc cuprates, iron pnictides, or heavy-fermion systems, superconductivity emerges in the proximity of an electronic instability. Identifying unambiguously the pairing mechanism remains nevertheless an enormous challenge. Among these systems, the orthorhombic uranium ferromagnetic superconductors have a unique position, notably because magnetic fields couple directly to ferromagnetic order, leading to the fascinating discovery of the reemergence of superconductivity in URhGe at a high field. Here we show that uniaxial stress is a remarkable tool allowing the fine-tuning of the pairing strength. With a relatively small stress, the superconducting phase diagram is spectacularly modified, with a merging of the low- and high-field superconducting states and a significant enhancement of the superconductivity. The superconducting critical temperature increases both at zero field and under a field, reaching 1 K, more than twice higher than at ambient pressure. This enhancement of superconductivity is shown to be directly related to a change of the magnetic dimensionality detected from an increase of the transverse magnetic susceptibility: In addition to the Ising-type longitudinal ferromagnetic fluctuations, transverse magnetic fluctuations also play an important role in the superconducting pairing.
Point-contact electron tunneling into the high-Tc superconductor Y-Ba-Cu-O

Science.gov (United States)

Kirk, M. D.; Smith, D. P. E.; Mitzi, D. B.; Sun, J. Z.; Webb, D. J.

1987-06-01

Results are reported from a study of electron tunneling into bulk samples of the new high-Tc superconductor Y-Ba-Cu-O using point-contact tunneling. Based on a superconductive tunneling interpretation, the results show exceptionally large energy gaps in these materials (roughly 2Delta = 100 MeV), implying 2Delta/kBTc = about 13. Similar values were found for La-Sr-Cu-O. The structure in the I-V curves is also similar to that seen in La-Sr-Cu-O. From the asymmetries observed in the I-V characteristics, it is inferred that the natural tunneling barrier on this material is of the Schottky type.
Dependence of the residual surface resistance of superconducting radio frequency cavities on the cooling dynamics around Tc

Science.gov (United States)

Romanenko, A.; Grassellino, A.; Melnychuk, O.; Sergatskov, D. A.

2014-05-01

We report a strong effect of the cooling dynamics through Tc on the amount of trapped external magnetic flux in superconducting niobium cavities. The effect is similar for fine grain and single crystal niobium and all surface treatments including electropolishing with and without 120 °C baking and nitrogen doping. Direct magnetic field measurements on the cavity walls show that the effect stems from changes in the flux trapping efficiency: slow cooling leads to almost complete flux trapping and higher residual resistance, while fast cooling leads to the much more efficient flux expulsion and lower residual resistance.
Superconducting properties of magnetron sputtered high T/sub c/ thin films containing oxide compounds of yttrium, bismuth, or thallium

International Nuclear Information System (INIS)

Kang, J.H.; Kampwirth, R.T.; Gray, K.E.

1989-01-01

The authors have used multiple source magnetron sputtering to prepare thin films of Y-Ba-Cu-O, Bi-Ca-Sr-Cu-O, and Tl-Ca-Ba-Cu-O on (100) SrTiO/sub 3/, (100) MgO, and ZrO/sub 2/-9%Y/sub 2/O/sub 3/ substrates. Y-Ba-Cu-O films grow best on SrTiO/sub 3/ with mostly an a-axis orientation. Stoichiometry, particularly the Ba/Ca ratio must be within 2% of the correct value to obtain narrow ΔT/sub c/ transitions. Conversely the 80K phase of Bi-Ca-Sr-Cu-O films grows best on MgO substrates and has a predominant c-axis orientation. The requirements on composition are less stringent, however, the annealing temperature must be held within a narrow around 865 0 C to obtain the best films. The best films of Tl-Ca-Ba-Cu-O compounds are grown on (100) oriented and polycrystalline ZrO/sub 2/ substrates. The highest transition temperature, T/sub c0/, where the resistance goes zero is about 114K in the Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ phase and 100-105K in Tl/sub 2/Ba/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ and Tl/sub 1/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ phase samples. The upper critical field measurements show high anisotropies in the critical field slopes (≥70 for Tl-Ba-Ca-Cu-O compounds and ∼15 for Bi-Sr-Ca-Cu-O compounds), as might be expected from highly oriented materials. The authors compare the preparation conditions and superconducting properties, including T/sub c/, ΔT/sub c/, dB/sub c2//dT (parallel and perpendicular to film surface), of all three compounds
Running Performance of a Pinning-Type Superconducting Magnetic Levitation Guide

International Nuclear Information System (INIS)

Okano, M; Iwamoto, T; Furuse, M; Fuchino, S; Ishii, I

2006-01-01

A pinning-type superconducting magnetic levitation guide with bulk high-Tc superconductors was studied for use as a goods transportation system, an energy storage system, etc. A superconducting magnetic levitation running test apparatus with a circular track of ca. 38 m length, 12 m diameter, which comprises the magnetic rail constituted by Nd-B-Fe rare-earth permanent magnets and steel plates, was manufactured to examine loss and high-speed performance of the magnetic levitation guide. Running tests were conducted in air. These tests clarify that a vehicle supported by a superconducting magnetic levitation guide runs stably at speeds greater than 42 km/h above the circular track
Running Performance of a Pinning-Type Superconducting Magnetic Levitation Guide

Science.gov (United States)

Okano, M.; Iwamoto, T.; Furuse, M.; Fuchino, S.; Ishii, I.

2006-06-01

A pinning-type superconducting magnetic levitation guide with bulk high-Tc superconductors was studied for use as a goods transportation system, an energy storage system, etc. A superconducting magnetic levitation running test apparatus with a circular track of ca. 38 m length, 12 m diameter, which comprises the magnetic rail constituted by Nd-B-Fe rare-earth permanent magnets and steel plates, was manufactured to examine loss and high-speed performance of the magnetic levitation guide. Running tests were conducted in air. These tests clarify that a vehicle supported by a superconducting magnetic levitation guide runs stably at speeds greater than 42 km/h above the circular track.
Superconductivity in volumetric and film ceramics Bi-Sr-Ca-Cu-O

Energy Technology Data Exchange (ETDEWEB)

Sukhanov, A A; Ozmanyan, Kh R; Sandomirskij, B B

1988-07-10

A superconducting transition with T/sub c0/=82-95 K and T/sub c/(R=0)=82-72 K was observed in volumetric and film Bi(Sr/sub 1-x/Ca/sub x/)/sub 2/Cu/sub 3/O/sub y/ samples obtained by solid-phase reaction. Temperature dependences of resistance critical current and magnetic susceptibility are measured.
High-Tc copper oxide superconductors and related novel materials dedicated to prof K. A. Müller on the occasion of his 90th birthday

CERN Document Server

Keller, Hugo; Bianconi, Antonio

2017-01-01

Authored by many of the world's leading experts on high-Tc superconductivity, this volume presents a panorama of ongoing research in the field, as well as insights into related multifunctional materials. The contributions cover many different and complementary aspects of the physics and materials challenges, with an emphasis on superconducting materials that have emerged since the discovery of the cuprate superconductors, for example pnictides, MgB2, H2S and other hydrides. Special attention is also paid to interface superconductivity. In addition to superconductors, the volume also addresses materials related to polar and multifunctional ground states, another class of materials that owes its discovery to Prof. Müller's ground-breaking research on SrTiO3.
Appearance of ferroelectricity by suppressing superconductivity in nanoparticle dispersed glassy precursor for high Tc superconductor

International Nuclear Information System (INIS)

Mukherjee, Soma; Chaudhuri, B.K.; Sakata, H.

2003-01-01

The multicomponent Bi 1.8 Pb 0.3 Sr 2 Ca 2 Cu 2.8 K 0.2 O δ (FG) glass is found to show ferroelectric (FE) transition around T fc = 530K. Microstructural (TEM) studies of these glasses indicated the presence of nano-crystalline particles/ clusters (∼10-30 nm size). In this glass-nanoparticle composite (GNC), presence of ferroelectric nano-particles/ islands is considered to be responsible for the FE behavior. The K-free FG type glasses showing no dielectric anomaly (or ferroelectricity) are precursors of high T c superconductors which become superconductors (T c ∼80K) by annealing around 840 degC. The K-doped (FG) GNC is, however, not superconducting in the corresponding annealed phase which indicates suppression of superconductivity due to the presence of K or by the appearance of ferroelectricity. Transport and dielectric properties of both K doped and undoped GNC have been studied and they are found to be semiconducting and follow non-adiabatic small polaron hopping conduction mechanism. (author)
Modeling and Optimization of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applicaitons

Science.gov (United States)

Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.; Burns, M. J.; Kleinsasser, A. W.; Delin, K. A.; Vasquez, R. P.

1996-01-01

The development of a YBa(sub 2)Cu(sub 3)O(sub 7-(kronecker delta))(YBCO) hot-electron bolometer (HEB) quasioptical mixer for a 2.5 heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate. The mixer performance expected for this device is analyzed in the framework of a two-temperature model which includes heating both of the electrons and the lattice. Also, the contribution of heat diffusion from the film through the substrate and from the film to the normal metal contacts is evaluated....a single sideband temperature of less than 2000k is predicted.
Lateral restorable characteristics of the high-Tc superconducting maglev vehicle above the permanent magnet guideway

International Nuclear Information System (INIS)

Ma, G.T.; Wang, J.S.; Lin, Q.X.; Liu, M.X.; Deng, Z.G.; Li, X.C.; Liu, H.F.; Zheng, J.; Wang, S.Y.

2009-01-01

The lateral restorable characteristics of a translational symmetry high-T c superconducting maglev system are investigated by measuring its resonant frequency (f RF ) after a lateral displacement. The difference between whether this lateral displacement is restorable, meaning elastic or inelastic, is determined by whether or not the maglev body returns to its original position after a lateral displacement. The maximum restorable lateral displacement (δ MRLD ) is determined by the sudden change of the f RF vs. the maximum lateral displacement (δ MLD ) curve. The f RF of the high-T c superconducting maglev system with different field-cooling height (FCH) and working height (WH) was obtained from the frequency domain vibration curve which was measured by a vibration measurement system. The results showed that, the δ MRLD was reduced when the WH was decreased. The maximum restorable guidance force (F MRGF ) was found to not always increase with the lowering of the WH for the same FCH. The lateral restorable stiffness (k LRS ) was always enhanced with the decrease of the WH. The decrease of the δ MRLD with the WH is interpreted by the fact that, the tangential field component (ΔH) across the surface of the high-T c superconductor (HTSC) is easier to exceed the J c λ value (J c is the critical current density and λ is the London penetration depth) when the WH is lowered, and this makes the trapped flux lines become more susceptible in escaping its pinning sites.
Superconducting Film Flux Transformer for a Sensor of a Weak Magnetic Field

International Nuclear Information System (INIS)

Ichkitidze, L; Mironyuk, A

2012-01-01

The object of study is a superconducting film flux transformer in the form of a square shaped loop with the tapering operative strip used in a sensor of a weak magnetic field. The magnetosensitive film element based on the giant magnetoresistance effect is overlapped with the tapering operative strip of the flux transformer; it is separated from the latter by the insulator film. It is shown that the topological nanostructuring of the operative strip of the flux transformer increases its gain factor by one or more orders of magnitude, i.e. increases its efficiency, which leads to a significant improvement of important parameters of a magnetic-field sensor.

Structural and superconducting properties of sputter-deposited niobium films for applications in RF accelerating cavities

CERN Document Server

Peck, M A

2000-01-01

The present work presents the results of a systematic study of superconducting and structural properties of niobium films sputter deposited onto the inner walls of radiofrequency copper resonators. The measured superconducting quantities include the surface resistance, the critical temperature, the penetration depth and the upper and lower critical fields. In addition to films grown with different discharge gases (Xe, Kr, Ar, Ne and Ar-Ne mixtures) and to films grown on substrates prepared under different conditions, the study also includes massive niobium cavities. The surface resistance is analysed in terms of its dependence on the temperature and on the rf field amplitude and, when possible, compared to theoretical predictions. In general, good agreement with BCS theory is observed. All experimental results are presented in the form of a simple, but adequate parameterisation. The residual resistance is observed to be essentially uncorrelated with the other variables, but strongly dependent on the macroscop...
Superconducting magnets in high energy physics

International Nuclear Information System (INIS)

Prodell, A.G.

1978-01-01

The applications of superconducting magnets in high energy physics in the last ten years have made feasible developments which are vital to high energy research. These developments include high magnetic field, large volume detectors, such as bubble chambers, required for effective resolution of high energy particle trajectories, particle beam transport magnets, and superconducting focusing and bending magnets for the very high energy accelerators and storage rings needed to pursue the study of interactions between elementary particles. The acceptance of superconductivity as a proven technology in high energy physics was reinforced by the recognition that the existing large accelerators using copper-iron magnets had reached practical limits in terms of magnetic field intensity, cost, space, and energy usage, and that large-volume, high-field, copper-iron magnets were not economically feasible. Some of the superconducting magnets and associated systems being used in and being developed for high energy physics are described
Three-terminal devices of high-Tc superconductors: A status report and future challenges

International Nuclear Information System (INIS)

Kung, Pang-Jen; Carnegie-Mellon Univ., Pittsburgh, PA

1992-01-01

A study has been conducted on the recent progress of the three-terminal devices with transistor-like characteristics fabricated from the high-T c superconducting materials. This study explored the operating principles and characteristics of these devices in relation to the relevant materials and techniques. A comparison of a variety of techniques for superconducting thin film deposition will be given. This study indirates that the feasibility of fabricating hybrid devices composed of semiconductors and superconductors appear to be the key issue to push forward the applications of high-T c superconductors in microelectronics. The junction field-effect transistors with a semiconductor base controlled by the proximity effect are likely to be more manufacturable. The factors that influence the operating reliability of devices and the problems arising from integrating and packaging the devices will also be discussed
High temperature superconducting devices for SQUIDs, HF- and FIR-applications. Subproject: Thin-film heterostructures for devices and loss mechanisms in HTS. Final report

International Nuclear Information System (INIS)

Froehlich, O.

1994-06-01

The successful use of electronic devices fabricated from the High Temperature Superconductors (HTS) in SQUID systems as well as HF- and FIR-applications requires the development of a suitable thin-film and device technology. Within the present research project we successfully established the technological base for the deposition and patterning of epitaxial HTS thin-films (YBaCuO, NdCeCuO) and heterostructures of HTS and insulating materials (e.g. NdGaO 3 ). YBaCuO/NdCeCuO superlattices could be successfully fabricated such that both components of the hterostructure were in a superconducting state. This allows for the fabrication and study of superconducting p-n structures. With respect to the fabrication of single grain boundary Josephson junctions based on the bicrystal technique we could establish an international leadership. The small spread of the junction parameters (∝20%) allowed the controllable fabrication of simple devices such as SQUIDs or flux-flow transistors. By the development of a new measuring technique the homogeneity of the critical current density distribution in grain-boundary junctions could be investigated on a sub-μm-scale. Within this project we also could establish a good understanding of the physical background of the transport phenomena in the mixed state of HTS in the presence of a temperature gradient. (orig./MM) [de
The preparation of Nb3Ge thin film superconductors in a UHV evaporation and sputter device

International Nuclear Information System (INIS)

Krevet, B.; Schauer, W.; Wuechner, F.

1978-10-01

Thin film techniques like evaporation or sputtering are remarkbly suitable to vary the metallurgical and physical properties of superconductors in a wide range. In the case of the A15-compound Nb 3 Ge only these preparation techniques allow us to produce a metastable pure phase in stoichiometric composition and to study its superconducting properties. The presen report describes two UHV-plants to produce superconducting films by multisource coevaporation and cosputtering. Of special importance are the constancy, monitoring and control of the evaporation rate, and the thermalization of the sputter components on the other hand. The experimental methods used are explained in detail and discussed together with the results of Nb 3 Ge films. With the preparation parameters suitably chosen both techniques allow to prepare reproducibly Nb 3 Ge films with 21 K transition temperature (onset); under optimized conditions Tc values up to 22.3 K have been reached. (orig.) [de
Ab initio molecular-orbital study on electron correlation effects in CuO6 clusters relating to high-Tc superconductivity

International Nuclear Information System (INIS)

Yamamoto, S.; Yamaguchi, K.; Nasu, K.

1990-01-01

Ab initio molecular-orbital calculations for CuO 6 clusters have been performed to elucidate the electronic structures of undoped and doped copper oxides, which are of current interest in relation to high-T c superconductivity. The electron correlation effects for these species are thoroughly investigated by the full-valence configuration-interaction method and the complete-active-space self-consistent-field method. The electron correlation effect is relatively simple for the A g state (σ hole), whereas pair excitations and spin-flip excitations give sizable contributions to the configuration-interaction wave function for the B state (in-plane π hole). Implications of these results are discussed in relation to the mechanisms of the high-T c superconductivity
The effect of ammonia intercalation on the superconducting ...

African Journals Online (AJOL)

A theoretical investigation of the electronic properties of the relatively high-Tc alkali-metal doped superconducting fullerides when they are further exposed to ammonia molecules as dopants is presented. Our numerical method relies on a group theoretical technique for the formation of molecular orbitals (MO's) for the solid ...
Effect of superconducting transition on microcreep of high-TC ceramics

International Nuclear Information System (INIS)

Soldatov, V.P.; Natsik, V.D.; Chajkovskaya, N.M.

1991-01-01

Influence of N-S and S-N transition on microplastic deformation kinetics of YBa 2 Cu 3 O 7-δ ceramic samples by there deformation in liquid nitrogen under microscreep conditions is studied. Superconductivity disruption in the sample was achieved by critical value currents. It is shown, that N-S transition increases creep rate,whereas S-N transition slows it down. Microplastic deformation rate by sample state change may very by two-eight times. Influence of heat expansion on creep kinetics as probable associated effect is analyzed. Assumption is expressed, that stimulated transition effect on microplastic deformation of ceramic samples is related to change of their electron state in the area of Josephson contacts between grains
Magnetofingerprints of superconducting films: Vortex dynamics and mesoscopic-scale disorder

International Nuclear Information System (INIS)

Nowak, E.R.; Israeloff, N.E.; Goldman, A.M.

1994-01-01

The variations of voltage and voltage noise with magnetic field in c-axis-oriented DyBa 2 Cu 3 O 7-δ thin films exhibit reproducible, microstructure-dependent ''magnetofingerprints'' (MF's). The MF's can be scrambled with the reversal of the direction of the Lorentz force on field-induced vortices. Analysis of the noise suggests a strong dependence of the local free-energy landscape on vortex density similar to global frustration effects found in periodic superconducting networks. Above fields which roughly match vortex separation with mesoscopic-scale disorder in the films the noise and the fine structure of the MF's are suppressed, suggesting a crossover to a more weakly pinned vortex-liquid regime
Theory of novel normal and superconducting states in doped oxide high-Tc superconductors

International Nuclear Information System (INIS)

Dzhumanov, S.

2001-10-01

A consistent and complete theory of the novel normal and superconducting (SC) states of doped high-T c superconductors (HTSC) is developed by combining the continuum model of carrier self-trapping, the tight-binding model and the novel Fermi-Bose-liquid (FBL) model. The ground-state energy of carriers in lightly doped HTSC is calculated within the continuum model and adiabatic approximation using the variational method. The destruction of the long-range antiferromagnetic (AF) order at low doping x≥ x cl ≅0.015, the formation of the in-gap states or bands and novel (bi)polaronic insulating phases at x c2 ≅0.06-0.08, and the new metal- insulator transition at x≅x c2 in HTSC are studied within the continuum model of impurity (defect) centers and large (bi)polarons by using the appropriate tight-binding approximations. It is found that the three-dimensional (3d) large (bi)polarons are formed at ε ∞ /ε 0 ≤0.1 and become itinerant when the (bi)polaronic insulator-to-(bi)polaronic metal transitions occur at x x c2 . We show that the novel pseudogapped metallic and SC states in HTSC are formed at x c2 ≤x≤x p ≅0.20-0.24. We demonstrate that the large polaronic and small BCS-like pairing pseudogaps opening in the excitation spectrum of underdoped (x c2 BCS =0.125), optimally doped (x BCS o ≅0.20) and overdoped (x>x o ) HTSC above T c are unrelated to superconductivity and they are responsible for the observed anomalous optical, transport, magnetic and other properties of these HTSC. We develop the original two-stage FBL model of novel superconductivity describing the combined novel BCS-like pairing scenario of fermions and true superfluid (SF) condensation scenario of composite bosons (i.e. bipolarons and cooperons) in any Fermi-systems, where the SF condensate gap Δ B and the BCS-like pairing pseudogap Δ F have different origins. The pair and single particle condensations of attracting 3d and two- dimensional (2d) composite bosons are responsible for
Tunability of resonance frequencies in a superconducting microwave resonator by using SrTiO sub 3 ferroelectric films

CERN Document Server

Sok, J; Lee, E H

1998-01-01

An applied dc voltage varies the dielectric constant of ferroelectric SrTiO sub 3 films. A tuning mechanism for superconducting microwave resonators was realized by using the variation in the dielectric constant of SrTiO sub 3 films. In order to estimate the values of the capacitance, C, and the loss tangent, tan delta, of SrTiO sub 3 ferroelectric capacitors, we used high-temperature superconducting microwave resonators which were composed of two ports, two poles, and dc bias circuits at the zero-field points. SrTiO sub 3 ferroelectric capacitors successfully controlled the resonant frequency of the resonator. Resonant frequencies of 3.98 GHz and 4.20 GHz were measured at bias voltages of 0 V and 50 V which correspond to capacitance values of 0.94 pF and 0.7pF, respectively. The values of the loss tangent, tan delta sub e sub f sub f , obtained in this measurements, were about 0.01.
Ultrasensitive interplay between ferromagnetism and superconductivity in NbGd composite thin films

Science.gov (United States)

Bawa, Ambika; Gupta, Anurag; Singh, Sandeep; Awana, V. P. S.; Sahoo, Sangeeta

2016-01-01

A model binary hybrid system composed of a randomly distributed rare-earth ferromagnetic (Gd) part embedded in an s-wave superconducting (Nb) matrix is being manufactured to study the interplay between competing superconducting and ferromagnetic order parameters. The normal metallic to superconducting phase transition appears to be very sensitive to the magnetic counterpart and the modulation of the superconducing properties follow closely to the Abrikosov-Gor’kov (AG) theory of magnetic impurity induced pair breaking mechanism. A critical concentration of Gd is obtained for the studied NbGd based composite films (CFs) above which superconductivity disappears. Besides, a magnetic ordering resembling the paramagnetic Meissner effect (PME) appears in DC magnetization measurements at temperatures close to the superconducting transition temperature. The positive magnetization related to the PME emerges upon doping Nb with Gd. The temperature dependent resistance measurements evolve in a similar fashion with the concentration of Gd as that with an external magnetic field and in both the cases, the transition curves accompany several intermediate features indicating the traces of magnetism originated either from Gd or from the external field. Finally, the signatures of magnetism appear evidently in the magnetization and transport measurements for the CFs with very low (<1 at.%) doping of Gd.
Plasma-assisted MOCVD growth of superconducting NbN thin films using Nb dialkylamide and Nb alkylimide precursors

International Nuclear Information System (INIS)

Liu Xiang; Ott, A.W.; Chang, R.P.H.; Babcok, J.R.; Belot, J.A.; Metz, M.V.; Marks, T.J.; Lane, M.A.; Kannewurf, C.R.

2001-01-01

The first example of the use of metal-organic precursors for depositing NbN superconducting thin films is described. The study, which employed niobium(IV) and niobium(V) pulsed source precursors and hydrazine plasma as the nitrogen source, indicates that T c is highly dependent on the lattice parameters and level of oxygen impurities, which are in turn governed by growth and post-deposition annealing temperatures. (orig.)
Development of high field superconducting magnet

International Nuclear Information System (INIS)

Irie, Fujio; Takeo, Masakatsu.

1986-01-01

Recently, in connection with nuclear fusion research, the development of high field superconducting magnets showed rapid progress. The development of high field magnets of 15 T class by the techniques of winding after heat treatment has been continued in various places, as these techniques are suitable to make large magnets. In 1985, Kyushu University attained the record of 15.5 T. However in high field magnets, there are many problems peculiar to them, and the basic research related to those is demanded. In this report, these general problems, the experience of the design and manufacture in Kyushu University and the related problems are described. The superconducting magnet installed in the Superconducting Magnet Research Center of Kyushu University attained the record of 15.5 T for the first time in March, 1985. In superconducting magnets, very difficult problem must be solved since superconductivity, heat and mechanical force are inter related. The problems of the wire materials for high field, the scale of high field magnets, the condition limiting mean current density, and the development of high field magnets in Kyushu University are described. (Kako, I.)
Multi-cell superconducting structures for high energy e+ e- colliders and free electron laser linacs

CERN Document Server

Sekutowicz, J

2008-01-01

This volume, which is the first in the EuCARD Editorial Series on “Accelerator Science and Technology”, is closely combined with the most advanced particle accelerators – based on Superconducting Radio Frequency (SRF) technology. In general, SRF research includes following areas: high gradient cavities, cavity prototyping, thin film technologies, large grain and mono-crystalline niobium and niobium alloys, quenching effects in superconducting cavities, SRF injectors, photo-cathodes, beam dynamics, quality of electron beams, cryogenics, high power RF sources, low level RF controls, tuners, RF power coupling to cavities, RF test infrastructures, etc. The monograph focuses on TESLA structures used in FLASH machine and planned for XFEL and ILC experiments.
Performance prediction of high Tc superconducting small antennas using a two-fluid-moment method model

Science.gov (United States)

Cook, G. G.; Khamas, S. K.; Kingsley, S. P.; Woods, R. C.

1992-01-01

The radar cross section and Q factors of electrically small dipole and loop antennas made with a YBCO high Tc superconductor are predicted using a two-fluid-moment method model, in order to determine the effects of finite conductivity on the performances of such antennas. The results compare the useful operating bandwidths of YBCO antennas exhibiting varying degrees of impurity with their copper counterparts at 77 K, showing a linear relationship between bandwidth and impurity level.
A low energy muon spin rotation and point contact tunneling study of niobium films prepared for superconducting cavities

Science.gov (United States)

Junginger, Tobias; Calatroni, S.; Sublet, A.; Terenziani, G.; Prokscha, T.; Salman, Z.; Suter, A.; Proslier, T.; Zasadzinski, J.

2017-12-01

Point contact tunneling and low energy muon spin rotation are used to probe, on the same samples, the surface superconducting properties of micrometer thick niobium films deposited onto copper substrates using different sputtering techniques: diode, dc magnetron and HIPIMS. The combined results are compared to radio-frequency tests performances of RF cavities made with the same processes. Degraded surface superconducting properties are found to correlate to lower quality factors and stronger Q-slope. In addition, both techniques find evidence for surface paramagnetism on all samples and particularly on Nb films prepared by HIPIMS.
Tuning of superconductivity by Ni substitution into noncentrosymmetric ThC o1 -xN ixC2

Science.gov (United States)

Grant, T. W.; Cigarroa, O. V.; Rosa, P. F. S.; Machado, A. J. S.; Fisk, Z.

2017-07-01

The recently discovered noncentrosymmetric superconductor ThCoC2 was observed to show unusual superconducting behavior with a critical temperature of Tc=2.65 K . Here we investigate the effect of nickel substitution on the superconducting state in ThC o1 -xN ixC2 . Magnetization, resistivity, and heat capacity measurements demonstrate Ni substitution has a dramatic effect with critical temperature increased up to Tc=12.1 K for x =0.4 Ni concentration, which is a rather high transition temperature for a noncentrosymmetric superconductor. In addition, the unusual superconducting characteristics observed in pure ThCoC2 appear to be suppressed or tuned with Ni substitution towards a more conventional fully gapped superconductor.
Superconductivity

International Nuclear Information System (INIS)

2007-01-01

During 2007, a large amount of the work was centred on the ITER project and related tasks. The activities based on low-temperature superconducting (LTS) materials included the manufacture and qualification of ITER full-size conductors under relevant operating conditions, the design of conductors and magnets for the JT-60SA tokamak and the manufacture of the conductors for the European dipole facility. A preliminary study was also performed to develop a new test facility at ENEA in order to test long-length ITER or DEMO full-size conductors. Several studies on different superconducting materials were also started to create a more complete database of superconductor properties, and also for use in magnet design. In this context, an extensive measurement campaign on transport and magnetic properties was carried out on commercially available NbTi strands. Work was started on characterising MgB 2 wire and bulk samples to optimise their performance. In addition, an intense experimental study was started to clarify the effect of mechanical loads on the transport properties of multi-filamentary Nb 3 Sn strands with twisted or untwisted superconducting filaments. The experimental activity on high-temperature superconducting (HTS) materials was mainly focussed on the development and characterisation of YBa 2 Cu 3 O 7-X (YBCO) based coated conductors. Several characteristics regarding YBCO deposition, current transport performance and tape manufacture were investigated. In the framework of chemical approaches for YBCO film growth, a new method, developed in collaboration with the Technical University of Cluj-Napoca (TUCN), Romania, was studied to obtain YBCO film via chemical solution deposition, which modifies the well-assessed metallic organic deposition trifluoroacetate (MOD-TFA) approach. The results are promising in terms of critical current and film thickness values. YBCO properties in films with artificially added pinning sites were characterised in collaboration with
Bibliography of high-T/sub c/ superconducting films

International Nuclear Information System (INIS)

Talvacchio, J.

1989-01-01

This document represents an effort to make bibliographic information on high-T/sub c/ superconductor films available to those who cannot access the on-line database at the Westinghouse R and D Center. The database contains a growing list of references -- approaching 5000 -- each of which is identified by a set of two-letter keywords. The database is used the same way as as INSPEC's, but its fixed set of standard keywords enables the user to obtain a complete list of references on keyworded topics. Since a single keyword (or search term) such as ''sputtering'' creates a bibliography that is too long for practical use, the database is used most effectively by combining a series of keywords using Boolean algebra to identify a handful of relevant references. The structure of this document is intended to present the subset of papers concerning high-T/sub c/ films (725 papers) in a compact format as a substitute for on-line searches. Rather than listing separate bibliographies for each of the 185 keywords, a single list of all the references is contained in Section 6, and indices based on the keywords are contained in Sections 3--5. This report is a true bibliography and does not contain any informative text. 725 refs

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