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Sample records for superconductors persistent magnetic

  1. Improvement of persistent magnetic field trapping in bulk Y-Ba-Cu-O superconductors

    Science.gov (United States)

    Chen, In-Gann; Weinstein, Roy

    1993-01-01

    For type-II superconductors, magnetic field can be trapped due to persistent internal supercurrent. Quasi-persistent magnetic fields near 2 T at 60 K (and 1.4 T at 77 K) have been measured in minimagnets made of proton-irradiated melt-textured Y-Ba-Cu-O (MT-Y123) samples. Using the trapping effect, high-field permanent magnets with dipole, quadrupole, or more complicated configurations can be made of existing MT-Y123 material, thus bypassing the need for high-temperature superconductor (HTS) wires. A phenomenological current model has been developed to account for the trapped field intensity and profile in HTS samples. This model is also a guide to select directions of materials development to further improve field trapping properties. General properties such as magnetic field intensities, spatial distributions, stabilities, and temperature dependence of trapped field are discussed.

  2. High temperature superconductor accelerator magnets

    NARCIS (Netherlands)

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and dev

  3. Hybrid superconductor magnet bearings

    Science.gov (United States)

    Chu, Wei-Kan

    1995-01-01

    Hybrid superconductor magnet bearings (HSMB's) utilize high temperature superconductors (HTS's) together with permanent magnets to form a frictionless interface between relatively rotating parts. They are low mass, stable, and do not incur expenditure of energy during normal operation. There is no direct physical contact between rotor and stator, and hence there is no wear and tear. However, just as any other applications of HTS's, it requires a very cold temperature to function. Whereas this might be perceived as a disadvantage on earth, it is of no great concern in space or on the moon. To astronomers, the moon is an excellent site for an observatory, but the cold and dusty vacuum environment on the moon precludes the use of mechanical bearings on the telescope mounts. Furthermore, drive mechanisms with very fine steps, and hence bearings with extremely low friction are needed to track a star from the moon, because the moon rotates very slowly. All aspects considered, the HSMB is about the only candidate that fits in naturally. Here, we present a design for one such bearing, capable of supporting a telescope that weighs about 3 lbs on Earth.

  4. Thin film superconductor magnetic bearings

    Science.gov (United States)

    Weinberger, Bernard R.

    1995-12-26

    A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

  5. Negative magnetic relaxation in superconductors

    Directory of Open Access Journals (Sweden)

    Krasnoperov E.P.

    2013-01-01

    Full Text Available It was observed that the trapped magnetic moment of HTS tablets or annuli increases in time (negative relaxation if they are not completely magnetized by a pulsed magnetic field. It is shown, in the framework of the Bean critical-state model, that the radial temperature gradient appearing in tablets or annuli during a pulsed field magnetization can explain the negative magnetic relaxation in the superconductor.

  6. Rotating superconductor magnet for producing rotating lobed magnetic field lines

    Science.gov (United States)

    Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.

    1978-01-01

    This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.

  7. High Temperature Superconductor Accelerator Magnets

    CERN Document Server

    AUTHOR|(CDS)2079328; de Rijk, Gijs; Dhalle, Marc

    2016-11-10

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding $20T$. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet is based on ReBCO coated conductor, which is assembled into a $10kA$ class Roebel cable. A new and optimized Aligned Block layout is used, which takes advantage of the anisotropy of the conductor. This is achieved by providing local alignment of the Roebel cable in the coil windings with the magnetic field lines. A new Network Model capable of analyzing transient electro-magnetic and thermal phenomena in coated conductor cables and coils is developed. This model is necessary to solve critical issues in coated conductor ac...

  8. Oscillatory persistent currents in quantum rings: Semiconductors versus superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Devreese, J.T., E-mail: jozef.devreese@ua.ac.b [TFVS, Universiteit Antwerpen, B-2020 Antwerpen (Belgium); COBRA, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Fomin, V.M. [TFVS, Universiteit Antwerpen, B-2020 Antwerpen (Belgium); COBRA, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Dept. of Theoretical Physics, State Univ. of Moldova, MD-2009 Chisinau (Moldova, Republic of); Institute for Integrative Nanosciences, IFW Dresden, D-01069 Dresden (Germany); Gladilin, V.N. [TFVS, Universiteit Antwerpen, B-2020 Antwerpen (Belgium); Dept. of Theoretical Physics, State Univ. of Moldova, MD-2009 Chisinau (Moldova, Republic of); Tempere, J. [TFVS, Universiteit Antwerpen, B-2020 Antwerpen (Belgium); Lyman Laboratory of Physics, Harvard University, Cambridge, MA 02138 (United States)

    2010-10-01

    Persistent currents are a hallmark of superconductivity in metals. To observe those dissipationless currents in a non-superconducting ring, the circumference of the ring must be short enough so that the phase coherence of the electronic wave functions is preserved around the loop. Recent progress in the fabrication of self-assembled semiconductor quantum rings (SAQRs), which can be filled with only a few (1-2) electrons, has offered the unique possibility to study the magnetic-field-induced oscillations in the persistent current carried by a single electron. In this paper, we discuss similarities and distinctions between the behavior of persistent currents in semiconductor and superconductor samples and give an overview of the recent results for oscillatory persistent currents in SAQRs. Although the real SAQR shape differs strongly from an idealized circular-symmetric open ring structure, the Aharonov-Bohm oscillations of the magnetization survive, as observed in low temperature magnetization measurements on In{sub x}Ga{sub 1-x}As/GaAs SAQRs.

  9. Studies on Magnetization Technique of High Temperature Superconductors

    OpenAIRE

    大橋, 忠巌; 荻原, 宏康

    1999-01-01

    It is known that permanent magnets produce magnetic fields up to 1T. On the other hand, magnetized high temperature superconductors can be used as "super"-permanent magnets which produce magnetic fields higher than 1T, because superconductors can trap higher magnetic fluxes than usual permanent magnets. In order to magnetize a YBCO bulk superconductor, there are two ways; a field cooling (FC) method and a zero field cooling (ZFC) method. FC is the way of magnetizing the superconductor by appl...

  10. Possible field-tuned superconductor-insulator transition in high-Tc superconductors: implications for pairing at high magnetic fields.

    Science.gov (United States)

    Steiner, M A; Boebinger, G; Kapitulnik, A

    2005-03-18

    The behavior of some high temperature superconductors (HTSC), such as La(2-x)Sr(x)CuO(4) and Bi(2)Sr(2-x)La(x)CuO(6 + delta), at very high magnetic fields, is similar to that of thin films of amorphous InOx near the magnetic-field-tuned superconductor-insulator transition. Analyzing the InOx data at high fields in terms of persisting local pairing amplitude, we argue by analogy that the local pairing amplitude also persists well into the dissipative state of the HTSCs, the regime commonly denoted as the "normal state" in very high magnetic field experiments.

  11. Permanent magnet with MgB2 bulk superconductor

    Science.gov (United States)

    Yamamoto, Akiyasu; Ishihara, Atsushi; Tomita, Masaru; Kishio, Kohji

    2014-07-01

    Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB2) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (cryocoolers, making MgB2 bulks promising for the next generation of Tesla-class permanent-magnet applications.

  12. Workshop on accelerator magnet superconductors. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    The workshop on accelerator magnet superconductors has gathered 102 registered participants from research laboratories, universities and industry. 8 European companies, active in superconducting materials and cables were present. This workshop has been organized to deal with the status of the world research and development on superconducting materials and cables for high field magnets (B > 10 T). The workshop has also reviewed the status of high temperature superconductors and transmission line cables for potential use in low field superconducting magnets for injectors and beam transfer lines, as well as cables for pulsed magnets that might be used in future hadron colliders or injectors.

  13. Superconductor Magnetization Modeling for the Numerical Calculation of Field Errors in Accelerator Magnets

    CERN Document Server

    Völlinger, C

    2002-01-01

    Superconducting magnets are obligatory today in order to provide the high magnetic fields that are needed for the acceleration of heavy particles in particle accelerators. The coils of such magnets are made of type II superconducting material and are exposed to a changing magnetic field which induces a so-called persistent current. Persistent currents are bipolar screening currents that do not decay, but persist due to the lack of resistivity in the superconductor. This way, they are the source of a superconductor magnetization in the coil which disturbs the field quality in the magnet aperture. In the framework of this thesis, a macroscopic superconductor model for the calculation of the magnetization of a thin superconducting cylinder of type II material has been developed. The model considers the dependency of the induced current density on the applied field as well as the local distribution of the magnetic induction within the superconductor. Both, the one-dimensional case of a homogeneous change of an ex...

  14. Performance of ceramic superconductors in magnetic bearings

    Science.gov (United States)

    Kirtley, James L., Jr.; Downer, James R.

    1993-01-01

    Magnetic bearings are large-scale applications of magnet technology, quite similar in certain ways to synchronous machinery. They require substantial flux density over relatively large volumes of space. Large flux density is required to have satisfactory force density. Satisfactory dynamic response requires that magnetic circuit permeances not be too large, implying large air gaps. Superconductors, which offer large magnetomotive forces and high flux density in low permeance circuits, appear to be desirable in these situations. Flux densities substantially in excess of those possible with iron can be produced, and no ferromagnetic material is required. Thus the inductance of active coils can be made low, indicating good dynamic response of the bearing system. The principal difficulty in using superconductors is, of course, the deep cryogenic temperatures at which they must operate. Because of the difficulties in working with liquid helium, the possibility of superconductors which can be operated in liquid nitrogen is thought to extend the number and range of applications of superconductivity. Critical temperatures of about 98 degrees Kelvin were demonstrated in a class of materials which are, in fact, ceramics. Quite a bit of public attention was attracted to these new materials. There is a difficulty with the ceramic superconducting materials which were developed to date. Current densities sufficient for use in large-scale applications have not been demonstrated. In order to be useful, superconductors must be capable of carrying substantial currents in the presence of large magnetic fields. The possible use of ceramic superconductors in magnetic bearings is investigated and discussed and requirements that must be achieved by superconductors operating at liquid nitrogen temperatures to make their use comparable with niobium-titanium superconductors operating at liquid helium temperatures are identified.

  15. Numerical analysis of thermally actuated magnets for magnetization of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Li Quan; Yan Yu; Rawlings, Colin; Coombs, Tim, E-mail: ql229@cam.ac.u [EPEC Superconductivity Group, Engineering Department, University of Cambridge, Trumpington Street. Cambridge, CB2 1PZ (United Kingdom)

    2010-06-01

    Superconductors, such as YBCO bulks, have extremely high potential magnetic flux densities, comparing to rare earth magnets. Therefore, the magnetization of superconductors has attracted broad attention and contribution from both academic research and industry. In this paper, a novel technique is proposed to magnetize superconductors. Unusually, instead of using high magnetic fields and pulses, repeatedly magnetic waves with strength of as low as rare earth magnets are applied. These magnetic waves, generated by thermally controlling a Gadolinium (Gd) bulk with a rare earth magnet underneath, travel over the flat surface of a YBCO bulk and get trapped little by little. Thus, a very small magnetic field can be used to build up a very large magnetic field. In this paper, the modelling results of thermally actuated magnetic waves are presented showing how to transfer sequentially applied thermal pulses into magnetic waves. The experiment results of the magnetization of YBCO bulk are also presented to demonstrate how superconductors are progressively magnetized by small magnetic field

  16. Permanent magnet with MgB{sub 2} bulk superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Akiyasu, E-mail: yamamoto@appchem.t.u-tokyo.ac.jp [The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Ishihara, Atsushi; Tomita, Masaru [Railway Technical Research Institute, 2-8-38 Hikari, Kokubunji, Tokyo 185-8540 (Japan); Kishio, Kohji [The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

    2014-07-21

    Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB{sub 2}) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB{sub 2} permanent bulk magnet was determined. Because MgB{sub 2} is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB{sub 2} bulks promising for the next generation of Tesla-class permanent-magnet applications.

  17. Magnetic chains on a triplet superconductor.

    Science.gov (United States)

    Sacramento, P D

    2015-11-11

    The topological state of a two-dimensional triplet superconductor may be changed by an appropriate addition of magnetic impurities. A ferromagnetic magnetic chain at the surface of a superconductor with spin-orbit coupling may eliminate the edge states of a finite system giving rise to localized zero modes at the edges of the chain. The coexistence/competition between the two types of zero modes is considered. The reduction of the system to an effective 1d system gives partial information on the topological properties but the study of the two sets of zero modes requires a two-dimensional treatment. Increasing the impurity density from a magnetic chain to magnetic islands leads to a finite Chern number. At half-filling small concentrations are enough to induce chiral modes.

  18. Building blocks for correlated superconductors and magnets

    Directory of Open Access Journals (Sweden)

    J. L. Sarrao

    2015-04-01

    Full Text Available Recent efforts at Los Alamos to discover strongly correlated superconductors and hard ferromagnets are reviewed. While serendipity remains a principal engine of materials discovery, design principles and structural building blocks are beginning to emerge that hold potential for predictive discovery. Successes over the last decade with the so-called “115” strongly correlated superconductors are summarized, and more recent efforts to translate these insights and principles to novel hard magnets are discussed. While true “materials by design” remains a distant aspiration, progress is being made in coupling empirical design principles to electronic structure simulation to accelerate and guide materials design and synthesis.

  19. Building blocks for correlated superconductors and magnets

    Energy Technology Data Exchange (ETDEWEB)

    Sarrao, J. L.; Ronning, F.; Bauer, E. D.; Batista, C. D.; Zhu, J.-X.; Thompson, J. D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2015-04-01

    Recent efforts at Los Alamos to discover strongly correlated superconductors and hard ferromagnets are reviewed. While serendipity remains a principal engine of materials discovery, design principles and structural building blocks are beginning to emerge that hold potential for predictive discovery. Successes over the last decade with the so-called “115” strongly correlated superconductors are summarized, and more recent efforts to translate these insights and principles to novel hard magnets are discussed. While true “materials by design” remains a distant aspiration, progress is being made in coupling empirical design principles to electronic structure simulation to accelerate and guide materials design and synthesis.

  20. Quench in high temperature superconductor magnets

    CERN Document Server

    Schwartz, J

    2013-01-01

    High field superconducting magnets using high temperature superconductors are being developed for high energy physics, nuclear magnetic resonance and energy storage applications. Although the conductor technology has progressed to the point where such large magnets can be readily envisioned, quench protection remains a key challenge. It is well-established that quench propagation in HTS magnets is very slow and this brings new challenges that must be addressed. In this paper, these challenges are discussed and potential solutions, driven by new technologies such as optical fiber based sensors and thermally conducting electrical insulators, are reviewed.

  1. Magnetic impurities in spin-split superconductors

    Science.gov (United States)

    van Gerven Oei, W.-V.; Tanasković, D.; Žitko, R.

    2017-02-01

    Hybrid semiconductor-superconductor quantum dot devices are tunable physical realizations of quantum impurity models for a magnetic impurity in a superconducting host. The binding energy of the localized subgap Shiba states is set by the gate voltages and external magnetic field. In this work we discuss the effects of the Zeeman spin splitting, which is generically present both in the quantum dot and in the (thin-film) superconductor. The unequal g factors in semiconductor and superconductor materials result in respective Zeeman splittings of different magnitude. We consider both classical and quantum impurities. In the first case we analytically study the spectral function and the subgap states. The energy of bound states depends on the spin-splitting of the Bogoliubov quasiparticle bands as a simple rigid shift. For the case of collinear magnetization of impurity and host, the Shiba resonance of a given spin polarization remains unperturbed when it overlaps with the branch of the quasiparticle excitations of the opposite spin polarization. In the quantum case, we employ numerical renormalization group calculations to study the effect of the Zeeman field for different values of the g factors of the impurity and of the superconductor. We find that in general the critical magnetic field for the singlet-doublet transition changes nonmonotonically as a function of the superconducting gap, demonstrating the existence of two different transition mechanisms: Zeeman splitting of Shiba states or gap closure due to Zeeman splitting of Bogoliubov states. We also study how in the presence of spin-orbit coupling, modeled as an additional noncollinear component of the magnetic field at the impurity site, the Shiba resonance overlapping with the quasiparticle continuum of the opposite spin gradually broadens and then merges with the continuum.

  2. Inhomogeneous magnetic field in AdS/CFT superconductor

    OpenAIRE

    Wen, Wen-Yu

    2008-01-01

    We study the holographically dual description of superconductor in (2+1)-dimensions in the presence of inhomogeneous magnetic field and observe that there exists type I and type II superconductor. A new feature of type changing is observed for type I superconductor near critical temperature.

  3. Stop of magnetic flux movement in levitating superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Smolyak, B.M., E-mail: b-smolyak@yandex.ru; Zakharov, M.S., E-mail: maksim.s.zakharov@gmail.com

    2017-01-15

    Highlights: • A direct experimental study of magnetic flux creep in the levitating superconductor. • When a levitating object is in a fixed position, magnetic flux movement is observed. • Levitation stops flux creep process. - Abstract: A phenomenon of magnetic relaxation stopping in a levitating superconductor was studied. It was experimentally shown that magnetic flux creep (diffusion of flux lines to regions with lower vortex density) is absent in magnetic suspension of the superconductor. Magnetic relaxation arises, when a rigid constraint that fixes a position of the superconductor relative to a magnet is imposed on a levitating object. It is assumed that oscillations of magnetic structure, which is due to free oscillations of the levitating superconductor, stop magnetic relaxation.

  4. Flywheel energy storage with superconductor magnetic bearings

    Energy Technology Data Exchange (ETDEWEB)

    Weinberger, Bernard R. (Avon, CT); Lynds, Jr., Lahmer (Glastonbury, CT); Hull, John R. (Hinsdale, IL)

    1993-01-01

    A flywheel having superconductor bearings has a lower drag to lift ratio that translates to an improvement of a factor of ten in the rotational decay rate. The lower drag results from the lower dissipation of melt-processed YBCO, improved uniformity of the permanent magnet portion of the bearings, operation in a different range of vacuum pressure from that taught by the art, and greater separation distance from the rotating members of conductive materials.

  5. High temperature superconductor cable concepts for fusion magnets

    CERN Document Server

    AUTHOR|(CDS)2078397

    2013-01-01

    Three concepts of high temperature superconductor cables carrying kA currents (RACC, CORC and TSTC) are investigated, optimized and evaluated in the scope of their applicability as conductor in fusion magnets. The magnetic field and temperature dependence of the cables is measured; the thermal expansion and conductivity of structure, insulation and filling materials are investigated. High temperature superconductor winding packs for fusion magnets are calculated and compared with corresponding low temperature superconductor cases.

  6. Magnetic flux periodicities and finite momentum pairing in unconventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Loder, Florian

    2009-12-22

    This work contains a thorough study of the magnetic flux periodicity of loops of conventional and unconventional, especially d-wave, superconductors. Although already in 1961, several independent works showed that the flux period of a conventional superconducting loop is the superconducting flux quantum hc/2e, this question has never been investigated deeply for unconventional superconductors. And indeed, we show here that d-wave superconducting loops show a basic flux period of the normal flux quantum hc/e, a property originating from the nodal quasi-particle states. This doubling of the flux periodicity is best visible in the persistent current circulating in the loop, and it affects other properties of the superconductor such as the periodicity of d-wave Josephson junctions. In the second part of this work, the theory of electron pairing with finite center-of-mass momentum, necessary for the description of superconducting loops, is extended to systems in zero magnetic field. We show that even in the field free case, an unconventional pairing symmetry can lead to a superconducting ground state with finite-momentum electron pairs. Such a state has an inhomogeneous charge density and therefore is a basis for the description of coexistence of superconductivity and stripe order. (orig.)

  7. Quantum oscillations in superconductors in magnetic field

    Science.gov (United States)

    Gvozdikov, Vladimir M.; Gvozdikova, Mariya V.

    2000-07-01

    The Aharonov-Bohm oscillations (ABO) of the free energy, the critical temperature, and the magnetic susceptibility in a stack of hollow mesoscopic cylinders are calculated. It is shown that sinusoidal (in flux) ABO crosses over to the parabolic Little-Parks oscillations (LPO) when the diameter of cylinders exceeds the coherence length. The exponential temperature behaviour of the magnetic susceptibility is like that found in Ag cylinders with thin Nb coating [Czech. J. Physics 46 (1996) 2317]. The formal analogy between oscillations of the free energy in the Aharonov-Bohm system in question and the de Haas-van Alphen oscillations (dHvAO) in layered superconductors is discussed.

  8. Frequency dependent magnetization of superconductor strip

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Kailash Prasad [Landcare Research, Palmerston North (New Zealand); Raj, Ashish [Computer Science in Radiology, Weill Medical College, Cornell University, NY (United States); Brandt, Ernst Helmut [Max-Planck-Institut fuer Metallforschung, POB 800665, D-70506 Stuttgart (Germany); Sastry, Pamidi V P S S, E-mail: thakurk@landcareresearch.co.nz, E-mail: asr2004@med.cornell.edu, E-mail: ehb@mf.mpg.de, E-mail: pamidi@caps.fsu.edu [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States)

    2011-04-15

    The frequency dependence of magnetic ac loss of thin superconductor strip subjected to an ac magnetic field perpendicular to the surface of the strip is investigated by incorporating a flux creep model into the critical state model of Brandt and Indenbom. It is found that the reduced ac loss exhibits a maximum value at a frequency f{sub m}, which is a rapidly varying function of the applied ac magnetic field. At low magnetic field, f{sub m} becomes zero, and ac loss decreases with frequency as a power law ({approx}f{sup -2/n}). Whereas at high magnetic field f{sub m} becomes infinite and ac loss increases with frequency, still following the power law ({approx}f{sup 1/n}). The analytical results are substantiated with experimental data and the results of a 2D finite element simulation.

  9. Magnetic excitations in iron chalcogenide superconductors.

    Science.gov (United States)

    Kotegawa, Hisashi; Fujita, Masaki

    2012-10-01

    Nuclear magnetic resonance and neutron scattering experiments in iron chalcogenide superconductors are reviewed to make a survey of the magnetic excitations in FeSe, FeSe1-x Te x and alkali-metal-doped Ax Fe2-y Se2 (A = K, Rb, Cs, etc). In FeSe, the intimate relationship between the spin fluctuations and superconductivity can be seen universally for the variations in the off-stoichiometry, the Co-substitution and applied pressure. The isovalent compound FeTe has a magnetic ordering with different wave vector from that of other Fe-based magnetic materials. The transition temperature Tc of FeSe increases with Te substitution in FeSe1-x Te x with small x, and decreases in the vicinity of the end member FeTe. The spin fluctuations are drastically modified by the Te substitution. In the vicinity of the end member FeTe, the low-energy part of the spin fluctuation is dominated by the wave vector of the ordered phase of FeTe; however, the reduction of Tc shows that it does not support superconductivity. The presence of same wave vector as that of other Fe-based superconductors in FeSe1-x Te x and the observation of the resonance mode demonstrate that FeSe1-x Te x belongs to the same group as most of other Fe-based superconductors in the entire range of x, where superconductivity is mediated by the spin fluctuations whose wave vector is the same as the nesting vector between the hole pockets and the electron pockets. On the other hand, the spin fluctuations differ for alkali-metal-doped Ax Fe2-y Se2 and FeSe or other Fe-based superconductors in their wave vector and strength in the low-energy part, most likely because of the different Fermi surfaces. The resonance mode with different wave vector suggests that Ax Fe2-y Se2 has an exceptional superconducting symmetry among Fe-based superconductors.

  10. A novel heat engine for magnetizing superconductors

    Science.gov (United States)

    Coombs, T. A.; Hong, Z.; Zhu, X.; Krabbes, G.

    2008-03-01

    The potential of bulk melt-processed YBCO single domains to trap significant magnetic fields (Tomita and Murakami 2003 Nature 421 517-20 Fuchs et al 2000 Appl. Phys. Lett. 76 2107-9) at cryogenic temperatures makes them particularly attractive for a variety of engineering applications including superconducting magnets, magnetic bearings and motors (Coombs et al 1999 IEEE Trans. Appl. Supercond. 9 968-71 Coombs et al 2005 IEEE Trans. Appl. Supercond. 15 2312-5). It has already been shown that large fields can be obtained in single domain samples at 77 K. A range of possible applications exist in the design of high power density electric motors (Jiang et al 2006 Supercond. Sci. Technol. 19 1164-8). Before such devices can be created a major problem needs to be overcome. Even though all of these devices use a superconductor in the role of a permanent magnet and even though the superconductor can trap potentially huge magnetic fields (greater than 10 T) the problem is how to induce the magnetic fields. There are four possible known methods: (1) cooling in field; (2) zero field cooling, followed by slowly applied field; (3) pulse magnetization; (4) flux pumping. Any of these methods could be used to magnetize the superconductor and this may be done either in situ or ex situ. Ideally the superconductors are magnetized in situ. There are several reasons for this: first, if the superconductors should become demagnetized through (i) flux creep, (ii) repeatedly applied perpendicular fields (Vanderbemden et al 2007 Phys. Rev. B 75 (17)) or (iii) by loss of cooling then they may be re-magnetized without the need to disassemble the machine; secondly, there are difficulties with handling very strongly magnetized material at cryogenic temperatures when assembling the machine; thirdly, ex situ methods would require the machine to be assembled both cold and pre-magnetized and would offer significant design difficulties. Until room temperature superconductors can be prepared, the

  11. A novel heat engine for magnetizing superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Coombs, T A; Hong, Z; Zhu, X [Cambridge University Engineering Department, Trumpington Street, CB2 1PZ (United Kingdom); Krabbes, G [IFW Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany)

    2008-03-01

    The potential of bulk melt-processed YBCO single domains to trap significant magnetic fields (Tomita and Murakami 2003 Nature 421 517-20; Fuchs et al 2000 Appl. Phys. Lett. 76 2107-9) at cryogenic temperatures makes them particularly attractive for a variety of engineering applications including superconducting magnets, magnetic bearings and motors (Coombs et al 1999 IEEE Trans. Appl. Supercond. 9 968-71; Coombs et al 2005 IEEE Trans. Appl. Supercond. 15 2312-5). It has already been shown that large fields can be obtained in single domain samples at 77 K. A range of possible applications exist in the design of high power density electric motors (Jiang et al 2006 Supercond. Sci. Technol. 19 1164-8). Before such devices can be created a major problem needs to be overcome. Even though all of these devices use a superconductor in the role of a permanent magnet and even though the superconductor can trap potentially huge magnetic fields (greater than 10 T) the problem is how to induce the magnetic fields. There are four possible known methods: (1) cooling in field; (2) zero field cooling, followed by slowly applied field; (3) pulse magnetization; (4) flux pumping. Any of these methods could be used to magnetize the superconductor and this may be done either in situ or ex situ. Ideally the superconductors are magnetized in situ. There are several reasons for this: first, if the superconductors should become demagnetized through (i) flux creep, (ii) repeatedly applied perpendicular fields (Vanderbemden et al 2007 Phys. Rev. B 75 (17)) or (iii) by loss of cooling then they may be re-magnetized without the need to disassemble the machine; secondly, there are difficulties with handling very strongly magnetized material at cryogenic temperatures when assembling the machine; thirdly, ex situ methods would require the machine to be assembled both cold and pre-magnetized and would offer significant design difficulties. Until room temperature superconductors can be prepared, the

  12. Vibrations in Magnet/Superconductor Levitation Systems

    Institute of Scientific and Technical Information of China (English)

    F. Y. Alzoubi; H. M. Al-khateeb; M. K. Alqadi; N. Y. Ayoub

    2006-01-01

    The problem of a small magnet levitating above a very thin superconducting disc in the Meissner state is analysed. The dipole-dipole interaction model is employed to derive analytical expressions for the interaction energy, levitation force, magnetic stiffness and frequency of small vibrations about the equilibrium position in two different configurations, i.e. with the magnetic moment parallel and perpendicular to the superconductor. The results show that the frequency of small vibrations decreases with the increasing levitation height for a particular radius of the superconducting disc, which is in good agreement with the experimental results. However, the frequency increases monotomcally up to saturation by increasing the radius of the disc for a particular height of the magnet. In addition, the frequency of vibrations is higher when the system is in the vertical configuration than that when the system is in the horizontal configuration.

  13. Magnetic Excitations from Stripes in Cuprate Superconductors

    Science.gov (United States)

    Tranquada, J. M.; Woo, H.; Perring, T. G.; Goka, H.; Gu, G. D.; Xu, G.; Fujita, M.; Yamada, K.

    2004-03-01

    While it is generally believed that antiferromagnetic spin excitations play a significant role in the pairing mechanism of copper-oxide superconductors [1], the nature of the magnetic excitations themselves remains a matter of controversy. Recent measurements of the dispersion of spin excitations in superconducting YBa_2Cu_3O_6+x (YBCO) have attracted much attention. Here we present the results of comprehensive inelastic neutron scattering measurements of the momentum- and energy-dependent spectra of the magnetic fluctuations in La_0.875Ba_0.125CuO_4, which exhibits inhomogeneous, charge-stripe order. We will also point out universalities and differences in the magnetic excitation spectra compared to related charge-stripe ordered compounds and high-temperature superconductors, including La_2-xSr_xNiO4 and YBCO. JMT, HW, GDG and GX are supported by U.S. Department of Energy contract # DE-AC02-98CH1088 [1] J. Orenstein and A. J. Millis, Science 288, 468 (2000).

  14. High temperature superconductors for magnetic suspension applications

    Science.gov (United States)

    Mcmichael, C. K.; Cooley, R. S.; Chen, Q. Y.; Ma, K. B.; Lamb, M. A.; Meng, R. L.; Chu, C. W.; Chu, W. K.

    1994-01-01

    High temperature superconductors (HTS) hold the promise for applications in magnetic levitation bearings, vibration damping, and torque coupling. Traditional magnetic suspension systems require active feedback and vibration controls in which power consumption and low frequency vibration are among the major engineering concerns. HTS materials have been demonstrated to be an enabling approach towards such problems due to their flux trapping properties. In our laboratory at TCSUH, we have been conducting a series of experiments to explore various mechanical applications using HTS. We have constructed a 30 lb. model flywheel levitated by a hybrid superconducting magnetic bearing (HSMB). We are also developing a levitated and vibration-dampled platform for high precision instrumentation. These applications would be ideal for space usages where ambient temperature is adequate for HTS to operate properly under greatly reduced cryogenic requirements. We will give a general overview of these potential applications and discuss the operating principles of the HTS devices we have developed.

  15. Magnetization of two-dimensional superconductors with defects

    CERN Document Server

    Kashurnikov, V A; Zyubin, M V

    2002-01-01

    The new method for modeling the layered high-temperature superconductors magnetization with defects, based on the Monte-Carlo algorithm, is developed. Minimization of the free energy functional of the vortex two-dimensional system made it possible to obtain the equilibrium vortex density configurations and calculate the magnetization of the superconductor with the arbitrary defects distribution in the wide range of temperatures. The magnetic induction profiles and magnetic flux distribution inside the superconductor, proving the applicability of the Bean model, are calculated

  16. Transport and Magnetism in Mesoscopic Superconductors

    CERN Document Server

    Fauchère, A L

    1999-01-01

    Superconductivity, discovered by Kamerlingh Onnes in 1911, continues to be a fascinating subject of condensed matter physics today. Much interest has been devoted to the study of the superconductivity induced in a metal which by itself is not superconducting but is in electrical contact with a superconductor. As the carriers of superconductivity, the Cooper pairs, diffuse across the contact into the metal they remain correlated, although the pairing mechanism is lifted; we call this the proximity effect. The observation of these superconducting correlations has come within the reach of experiments in the last decade. With state-of-the-art fabrication techniques mesoscopic samples have been produced which are small and clean enough for the quantum mechanical coherence of the electrons to be preserved over the sample size. This theoretical thesis focuses on the variety of signatures of single-particle physics that appear in the electrical transport and the magnetic screening properties of these systems. We stud...

  17. Magnetic irreversibility in granular superconductors: ac susceptibility study

    Energy Technology Data Exchange (ETDEWEB)

    Perez, F.; Obradors, X.; Fontcuberta, J. (ICMAB, CSIC, Bellaterra, Barcelona (Spain)); Vallet, M.; Gonzalez-Calbet, J. (Lab. Magnetismo Aplicado, RENFE-U.C. Madrid, Las Matas (Spain))

    1991-12-01

    Ac susceptibility measurements of a ceramic weak-coupled superconductor in very low ac fields (2mG, 111Hz) are reported. We present evidence for the observation of the magnetic irreversibility following a ZFC-FC thermal cycling by means of ac susceptibilty measurements. It is shown that this technique also reflect local magnetic field effects in granular superconductors, as previously suggested in microwave surface resistance and I-V characteristics. (orig.).

  18. Stability of magnetic tip/superconductor levitation systems

    Institute of Scientific and Technical Information of China (English)

    M. K. Alqadi

    2015-01-01

    The vertical stability of a magnetic tip over a superconducting material is investigated by using the critical state and the frozen image models. The analytical expressions of the stiffness and the vibration frequency about the equilibrium position are derived in term of the geometrical parameters of the magnet/superconductor system. It is found that the stability of the system depends on the shape of the superconductor as well as its thickness.

  19. Exotic magnetic states in Pauli-limited superconductors.

    Science.gov (United States)

    Kenzelmann, M

    2017-03-01

    Magnetism and superconductivity compete or interact in complex and intricate ways. Here we review the special case where novel magnetic phenomena appear due to superconductivity, but do not exist without it. Such states have recently been identified in unconventional superconductors. They are different from the mere coexistence of magnetic order and superconductivity in conventional superconductors, or from competing magnetic and superconducting phases in many materials. We describe the recent progress in the study of such exotic magnetic phases, and articulate the many open questions in this field.

  20. Exotic magnetic states in Pauli-limited superconductors

    Science.gov (United States)

    Kenzelmann, M.

    2017-03-01

    Magnetism and superconductivity compete or interact in complex and intricate ways. Here we review the special case where novel magnetic phenomena appear due to superconductivity, but do not exist without it. Such states have recently been identified in unconventional superconductors. They are different from the mere coexistence of magnetic order and superconductivity in conventional superconductors, or from competing magnetic and superconducting phases in many materials. We describe the recent progress in the study of such exotic magnetic phases, and articulate the many open questions in this field.

  1. Probing High Temperature Superconductors with Magnetometry in Ultrahigh Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lu [Univ. of Michigan, Ann Arbor, MI (United States)

    2017-07-26

    The objective of this research is to investigate the high-field magnetic properties of high temperature superconductors, materials that conduct electricity without loss. A technique known as high-resolution torque magnetometry that was developed to directly measure the magnetization of high temperature superconductors. This technique was implemented using the 65 Tesla pulsed magnetic field facility that is part of the National High Magnetic Field Laboratory at Los Alamos National Laboratory. This research addressed unanswered questions about the interplay between magnetism and superconductivity, determine the electronic structure of high temperature superconductors, and shed light on the mechanism of high temperature superconductivity and on potential applications of these materials in areas such as energy generation and power transmission. Further applications of the technology resolve the novel physical phenomena such as correlated topological insulators, and spin liquid state in quantum magnets.

  2. Persistence of slow fluctuations in the overdoped regime of Ba (Fe1 -xRhx) 2As2 superconductors

    Science.gov (United States)

    Bossoni, L.; Moroni, M.; Julien, M. H.; Mayaffre, H.; Canfield, P. C.; Reyes, A.; Halperin, W. P.; Carretta, P.

    2016-06-01

    We present nuclear magnetic resonance evidence that very slow (≤1 MHz) spin fluctuations persist into the overdoped regime of Ba (Fe1 -xRhx) 2As2 superconductors. Measurements of the 75As spin echo decay rate, obtained both with Hahn Echo and Carr Purcell Meiboom Gill pulse sequences, show that the slowing down of spin fluctuations can be described by short-range diffusive dynamics, likely involving domain walls motions separating (π /a ,0 ) from (0 ,π /a ) correlated regions. This slowing down of the fluctuations is weakly sensitive to the external magnetic field and, although fading away with doping, it extends deeply into the overdoped regime.

  3. Lateral restoring force on a magnet levitated above a superconductor

    Science.gov (United States)

    Davis, L. C.

    1990-01-01

    The lateral restoring force on a magnet levitated above a superconductor is calculated as a function of displacement from its original position at rest using Bean's critical-state model to describe flux pinning. The force is linear for small displacements and saturates at large displacements. In the absence of edge effects the force always attracts the magnet to its original position. Thus it is a restoring force that contributes to the stability of the levitated magnet. In the case of a thick superconductor slab, the origin of the force is a magnetic dipole layer consisting of positive and negative supercurrents induced on the trailing side of the magnet. The qualitative behavior is consistent with experiments reported to date. Effects due to the finite thickness of the superconductor slab and the granular nature of high-Tc materials are also considered.

  4. Workshop on Accelerator Magnet Superconductors, Design and Optimization

    CERN Document Server

    WAMSDO Workshop

    2009-01-01

    This report contains the proceedings of the CARE-HHH-AMT Workshop on Accelerator Magnet Superconductors, Design and Optimization (WAMSDO) held at CERN from 19 to 23 May 2008. The needs in terms of superconducting magnets for the accelerator projects were discussed, mainly for the LHC interaction regions and injector upgrades, and for the GSI FAIR complex. The first part of the workshop focused on the development of superconductor and cables, i.e., low-loss Nb-Ti cables, Nb3Sn and high-temperature superconductors. An industry session summarized the actual plans and status of the activities in the main European industries. Then, a worldwide status of the high field magnets programme was presented. A special session was devoted to fast cycled magnets, including FAIR facilities and LHC injector upgrades. A final session focused on the optimization methods and numerical tools for magnet design.

  5. Permanent magnets composed of high temperature superconductors

    Science.gov (United States)

    Weinstein, Roy; Chen, In-Gann; Liu, Jay; Lau, Kwong

    1991-01-01

    A study of persistent, trapped magnetic field has been pursued with high-temperature superconducting (HTS) materials. The main effort is to study the feasibility of utilization of HTS to fabricate magnets for various devices. The trapped field, when not in saturation, is proportional to the applied field. Thus, it should be possible to replicate complicated field configurations with melt-textured YBa2Cu3O7 (MT-Y123) material, bypassing the need for HTS wires. Presently, materials have been developed from which magnets of 1.5 T, at 77 K, can be fabricated. Much higher field is available at lower operating temperature. Stability of a few percent per year is readily attainable. Results of studies on prototype motors and minimagnets are reported.

  6. Design features of internal tin superconductors for ITER magnetic system

    Energy Technology Data Exchange (ETDEWEB)

    Pantsyrnyi, V.I.; Shikov, A.K.; Nikulin, A.D.; Silaev, A.G.; Bel`akov, N.A.; Vdovin, V.F.; Semin, M.J. [Bochvar All-Russia Inst. of Inorganic Materials, Moscow (Russian Federation)

    1996-07-01

    The influence of parameters of internal tin superconductor design on the main working characteristics such as critical current density and hysteresis losses were analyzed. It was shown that having the value of hysteresis losses at the acceptable level of 400--600 mJ/cm{sup 3} the critical current density 20--30% higher than the value typical for bronze route processed superconductors was attainable in principle. The results of experimental work on the design of new types of internal tin superconductors for ITER magnetic system are given.

  7. Low field magnetic measurements on high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, G.; Murphy, S.D.; Li, Z.Y.; Stewart, A.M.; Bhagat, S.M. (Maryland Univ., College Park, MD (USA). Dept. of Physics and Astronomy)

    1989-09-01

    The authors report dc magnetization and ac susceptibility measurements on both micron size powders and sintered samples of several high temperature superconductors. The powder data confirm previous findings that the materials can be treated as conventional superconductors with s-wave pairing. The ac results on sintered slabs ar interpreted using Bean's model and yield the temperature dependence of the shielding current.

  8. Cryocooler applications for high-temperature superconductor magnetic bearings.

    Energy Technology Data Exchange (ETDEWEB)

    Niemann, R. C.

    1998-05-22

    The efficiency and stability of rotational magnetic suspension systems are enhanced by the use of high-temperature superconductor (HTS) magnetic bearings. Fundamental aspects of the HTS magnetic bearings and rotational magnetic suspension are presented. HTS cooling can be by liquid cryogen bath immersion or by direct conduction, and thus there are various applications and integration issues for cryocoolers. Among the numerous cryocooler aspects to be considered are installation; operating temperature; losses; and vacuum pumping.

  9. Magnetic Response in the Holographic Insulator/Superconductor Transition

    CERN Document Server

    Montull, Marc; Salvio, Alberto; Silva, Pedro J

    2012-01-01

    We study the magnetic response of holographic superconductors exhibiting an insulating "normal" phase. These materials can be realized as a CFT compactified on a circle, which is dual to the AdS Soliton geometry. We study the response under i) magnetic fields and ii) a Wilson line on the circle. Magnetic fields lead to formation of vortices and allows one to infer that the superconductor is of type II. The response to a Wilson line is in the form of Aharonov-Bohm-like effects. These are suppressed in the holographic conductor/superconductor transition but, instead, they are unsuppressed for the insulator case. Holography, thus, predicts that generically insulators display stronger Aharonov-Bohm effects than conductors. In the fluid-mechanical limit the AdS Soliton is interpreted as a supersolid. Our results imply that supersolids display unsuppressed Aharonov-Bohm (or "Sagnac") effects - stronger than in superfluids.

  10. Persistent ferromagnetism and topological phase transition at the interface of a superconductor and a topological insulator.

    Science.gov (United States)

    Qin, Wei; Zhang, Zhenyu

    2014-12-31

    At the interface of an s-wave superconductor and a three-dimensional topological insulator, Majorana zero modes and Majorana helical states have been proposed to exist respectively around magnetic vortices and geometrical edges. Here we first show that randomly distributed magnetic impurities at such an interface will induce bound states that broaden into impurity bands inside (but near the edges of) the superconducting gap, which remains open unless the impurity concentration is too high. Next we find that an increase in the superconducting gap suppresses both the oscillation magnitude and the period of the Ruderman-Kittel-Kasuya-Yosida interaction between two magnetic impurities. Within a mean-field approximation, the ferromagnetic Curie temperature is found to be essentially independent of the superconducting gap, an intriguing phenomenon due to a compensation effect between the short-range ferromagnetic and long-range antiferromagnetic interactions. The existence of robust superconductivity and persistent ferromagnetism at the interface allows realization of a novel topological phase transition from a nonchiral to a chiral superconducting state at sufficiently low temperatures, providing a new platform for topological quantum computation.

  11. Magnetic response of holographic Lifshitz superconductors: Vortex and Droplet solutions

    Energy Technology Data Exchange (ETDEWEB)

    Lala, Arindam, E-mail: arindam.lala@bose.res.in

    2014-07-30

    In this paper a holographic model of s-wave superconductor with anisotropic Lifshitz scaling has been considered. In the presence of an external magnetic field our holographic model exhibits both vortex and droplet solutions. Based on analytic methods we have shown that the anisotropy has no effect on the vortex and droplet solutions whereas it may affect the condensation. Our vortex solution closely resembles the Ginzburg–Landau theory and a relation between the upper critical magnetic field and superconducting coherence length has been speculated from this comparison. Using Sturm–Liouville method, the effect of anisotropy on the critical parameters in insulator/superconductor phase transitions has been analyzed.

  12. Development of the superconductors for ITER magnet system

    Science.gov (United States)

    Shikov, A.; Nikulin, A.; Silaev, A.; Vorobieva, A.; Pantsyrnyi, V.; Vedernikov, G.; Salunin, N.; Sudiev, S.

    1998-10-01

    A review is given of the present status of the development and production of Nb 3Sn and Nb-Ti superconductors for the Model Coils and the real Magnet System of the International Thermonuclear Experimental Reactor (ITER) in the Russian Federation Home Team. It is shown that Nb 3Sn bronze processed superconductors produced for the Model Central Solenoid Coil insert meet the ITER joint Central Team requirements. In particular, the critical current density, measued in non-Cu area is not less than 550 A/mm 2 for 12 T at 4.2 K, the level of hysteresis losses is not in excess of 200 mJ/cm 3, and the Cu-stabilizing shell resistivity ratio of Cr-plated wire is 150. Internal tin Nb 3Sn superconductor development and test results are presented, confirming the possibility of their application for the ITER Magnet System winding. Nb-Ti superconductors for PF coils properties have also been considered. The possibility of Nb 3Sn and Nb-Ti superconductor manufacture with the use of large composite billets up to 300 mm in dia is shown, creating the possibility for large scale industrial production (several tens of tons/year) of these materials for the ITER Magnet System.

  13. Holographic superconductors with Lifshitz scaling in external magnetic field

    CERN Document Server

    Zhao, Zixu; Jing, Jiliang

    2014-01-01

    We analytically study the holographic superconductors with Lifshitz scaling in presence of an external magnetic field. We observe that Lifshitz scaling can hinder the condensation to be formed, which can be used to back up the existing numerical results. Moreover, we find that the dynamical exponent $z$ does have effects on the upper critical magnetic field. However, we note that Lifshitz scaling does not modify the well-known relation obtained from the Ginzburg-Landau theory for the upper critical magnetic field.

  14. Local model for magnet-superconductor mechanical interaction: Experimental verification

    Science.gov (United States)

    Diez-Jimenez, Efren; Perez-Diaz, Jose-Luis; Garcia-Prada, Juan Carlos

    2011-03-01

    Several models exist for calculating superconducting repulsion forces in the Meissner state that are based on the method of images. The method of images, however, is limited to a small number of geometrical configurations that can be solved exactly, and the physical interpretation of the method is under discussion. A general local model based on the London equations and Maxwell's equations has been developed to describe the mechanics of the superconductor-permanent magnet system. Due to its differential form, this expression can be easily implemented in a finite elements analysis and, consequently, is easily applicable to any shape of superconductor in the Meissner state. It can solve both forces and torques. This paper reports different experiments undertaken in order to test the model's validity. The vertical forces and the angle of equilibrium between a magnet and a superconductor were measured, and a positive agreement between the experiments and theoretical calculations was found.

  15. Magnetic flux annihilation waves in inhomogeneous high-temperature superconductors

    NARCIS (Netherlands)

    Rudnev, IA; Khodot, AE; Eremin, AV; Mikhailov, BP

    2004-01-01

    The process of magnetic field penetration into polycrystalline high-T-c superconductors of the YBa2Cu3O7 - x and Bi2Sr2Ca2Cu3O10 - x systems has been studied using traditional magnetooptical methods and scanning Hall probe microscopy. It is established that remagnetization of a sample is accompanied

  16. Superconductor Requirements and Characterization for High Field Accelerator Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Barzi, E.; Zlobin, A. V.

    2015-05-01

    The 2014 Particle Physics Project Prioritization Panel (P5) strategic plan for U.S. High Energy Physics (HEP) endorses a continued world leadership role in superconducting magnet technology for future Energy Frontier Programs. This includes 10 to 15 T Nb3Sn accelerator magnets for LHC upgrades and a future 100 TeV scale pp collider, and as ultimate goal that of developing magnet technologies above 20 T based on both High Temperature Superconductors (HTS) and Low Temperature Superconductors (LTS) for accelerator magnets. To achieve these objectives, a sound conductor development and characterization program is needed and is herein described. This program is intended to be conducted in close collaboration with U.S. and International labs, Universities and Industry.

  17. Quaternary borocarbides: Relatively high T{sub c} intermetallic superconductors and magnetic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mazumdar, Chandan, E-mail: chandan.mazumdar@saha.ac.in [Saha Institute of Nuclear Physics, Kolkata 700064 (India); Nagarajan, R., E-mail: nagarajan@cbs.ac.in [University of Mumbai-Department of Atomic Energy Centre for Excellence in Basic Sciences, Santacruz (East), Mumbai 400 098 (India)

    2015-07-15

    Discovery of superconductivity in Y–Ni–B–C (T{sub c} ∼ 13 K) gave rise to the class of quaternary rare earth transition metal borocarbide superconductors. Before the discovery of Fe-based arsenide superconductors, this was the only class of materials containing a magnetic element, viz., Ni, yet exhibiting T{sub c}s > 5 K. Many members of this class have high T{sub c} (>10 K). T{sub c} of ∼23 K in Y–Pd–B–C system equaled the record T{sub c} known then, for intermetallics. Another feature that sets this class apart, is the occurrence of the exotic phenomenon of coexistence of superconductivity and magnetism at temperatures >5 K. Availability of large and electronically ‘clean’ single crystals and large Ginzburg-Landau (G–L) parameter, κ, have enabled detailed investigation of nonlocal effects of superconductivity. Intermediate value of upper critical field H{sub c2}, has enabled detailed investigation of superconductivity in this class, over the complete H–T plane. This has revealed details of anisotropy of superconductivity (e.g., a fourfold symmetry in the square a–b plane is found) and raised questions on the symmetry of order parameter. After a brief outline of the discovery, this article gives a summary of the materials and highlights of superconducting properties of this class of materials. Interesting results from studies, using various techniques, on YNi{sub 2}B{sub 2}C (T{sub c} ∼ 15 K) and LuNi{sub 2}B{sub 2}C (T{sub c} ∼ 16 K) are presented, including observation of unusual square vortex lattice and its structural transformation with H and T. With conduction electrons involved in the magnetic order of this class of superconductors, the interplay of superconductivity and magnetism is intimate in these magnetic superconductors. With T{sub c} (∼11 K) > T{sub N} (∼6 K) in ErNi{sub 2}B{sub 2}C, T{sub c} (∼8 K) = T{sub N} (∼8 K) in HoNi{sub 2}B{sub 2}C and T{sub c} (∼6 K) < T{sub N} (∼11 K) in DyNi{sub 2}B{sub 2}C, and

  18. Instability in the magnetic field penetration in type II superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Isaías G. de, E-mail: isaias@ufrrj.br

    2015-07-17

    Under the view of the time-dependent Ginzburg–Landau theory we have investigated the penetration of the magnetic field in the type II superconductors. We show that the single vortices, situated along the borderline, between the normal region channel and the superconducting region, can escape to regions still empty of vortices. We show that the origin of this process is the repulsive nature of vortex–vortex interaction, in addition to the non-homogeneous distribution of the vortices along the normal region channel. Using London theory we explain the extra gain of kinetic energy by the vortices situated along this borderline. - Highlights: • TDGL is used to study the magnetic field penetration in type II superconductors. • Instability process is found during the magnetic field penetration. • Vortices along the front of the normal region escape to superconducting region. • We explain the extra-gain of kinetic energy by vortices along the borderline.

  19. Distinct magnetic signatures of fractional vortex configurations in multiband superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R. M. da [Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil); Milošević, M. V.; Peeters, F. M. [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Domínguez, D. [Centro Atómico Bariloche, 8400 San Carlos de Bariloche, Río Negro (Argentina); Aguiar, J. Albino, E-mail: albino@df.ufpe.br [Departamento de Física, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil); Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil)

    2014-12-08

    Vortices carrying fractions of a flux quantum are predicted to exist in multiband superconductors, where vortex core can split between multiple band-specific components of the superconducting condensate. Using the two-component Ginzburg-Landau model, we examine such vortex configurations in a two-band superconducting slab in parallel magnetic field. The fractional vortices appear due to the band-selective vortex penetration caused by different thresholds for vortex entry within each band-condensate, and stabilize near the edges of the sample. We show that the resulting fractional vortex configurations leave distinct fingerprints in the static measurements of the magnetization, as well as in ac dynamic measurements of the magnetic susceptibility, both of which can be readily used for the detection of these fascinating vortex states in several existing multiband superconductors.

  20. About the Influence of the Magnetic Field Configuration on the Levitation Characteristics of the System Superconductor - Array of Magnets

    Science.gov (United States)

    Ermolaev, Yu. S.; Rudnev, I. A.

    2014-07-01

    Interaction of a superconductor with an array of magnets having different orientations of the magnetization vector is theoretically investigated. Based on a critical state model, the interaction force arising in the system superconductor - array of magnets is calculated by the method of finite elements. Optimal configurations of the magnetic system are established in which maximum values of both attractive and repulsive forces are created.

  1. Optical magnetic flux generation in superconductor

    Indian Academy of Sciences (India)

    Masayoshi Tonouchi

    2002-05-01

    The generation of the magnetic flux quanta inside the superconductors is studied as a new effect to destroy superconductivity using femtosecond (fs) laser. The vortices are successfully generated in the YBa2Cu3O7- thin film striplines by the fs laser. It is revealed that the vortex distribution in the strip reflects the fs laser beam profile.

  2. The Bean model of the critical state in a magnetically shielded superconductor filament

    Energy Technology Data Exchange (ETDEWEB)

    Yampolskii, S V [Institut fuer Materialwissenschaft, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany); Genenko, Y A [Institut fuer Materialwissenschaft, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany); Rauh, H [Institut fuer Materialwissenschaft, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany); Snezhko, A V [Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2006-06-01

    We study the magnetization of a cylindrical type-II superconductor filament covered by a coaxial soft-magnet sheath and exposed to an applied transverse magnetic field. Examining penetration of magnetic flux into the superconductor core of the filament on the basis of the Bean model of the critical state, we find that the presence of a non-hysteretic magnetic sheath can strongly enhance the field of full penetration of magnetic flux. The average magnetization of the superconductor/magnet heterostructure under consideration and hysteresis AC losses in the core of the filament are calculated as well.

  3. Antimagnets: controlling magnetic fields with superconductor-metamaterial hybrids

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Alvaro; Navau, Carles; Prat-Camps, Jordi; Chen Duxing, E-mail: alvar.sanchez@uab.cat [Grup d' Electromagnetisme, Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia (Spain)

    2011-09-15

    Magnetism is very important in various areas of science and technology, ranging from magnetic recording through energy generation to trapping cold atoms. Physicists have managed to master magnetism-to create and manipulate magnetic fields-almost at will. Surprisingly, there is at least one property that has been elusive until now: how to 'switch off' the magnetic interaction of a magnetic material with existing magnetic fields without modifying them. Here we introduce the antimagnet, a design that conceals the magnetic response of a given volume from its exterior, without altering the external magnetic fields, in some respects analogous to recent theoretical proposals for cloaking electromagnetic waves with metamaterials. However, unlike these devices, which require extreme material properties, our device is feasible and needs only two kinds of available materials: superconductors and isotropic magnetic materials. Antimagnets may have applications in magnetic-based medical techniques such as magnetic resonance imaging or in reducing the magnetic signature of vessels or planes.

  4. Properties of the superconductor in accelerator dipole magnets

    Science.gov (United States)

    Teravest, Derk

    Several aspects of the application of superconductors to high field dipole magnets for particle accelerators are discussed. The attention is focused on the 10 tesla (1 m model) magnet that is envisaged for the future Large Hadron Collider (LHC) accelerator. The basic motivation behind the study is the intention of employing superconductors to their utmost performance. An overview of practical supercomputers, their applications and their impact on high field dipole magnets used for particle accelerators, is presented. The LHC reference design for the dipole magnets is outlined. Several models were used to study the influence of a number of factors in the shape and in particular, the deviation from the shape that is due to the flux flow state. For the investigated extrinsic and intrinsic factors, a classification can be made with respect to the effect on the shape of the characteristic of a multifilamentary wire. The optimization of the coil structure for high field dipole magnets, with respect to the field quality is described. An analytical model for solid and hollow filaments, to calculate the effect of filament magnetization in the quality of the dipole field, is presented.

  5. Magnetic field in holographic superconductor with dark matter sector

    CERN Document Server

    Nakonieczny, L; Wysokinski, K I

    2015-01-01

    Based on the analytical technique the effect of the static magnetic field on the s-wave holographic superconductor with dark matter sector of U(1)-gauge field type coupled to the Maxwell field has been examined. In the probe limit, we obtained the mean value of the condensation operator. The nature of the condensate in an external magnetic field as well as the behaviour of the critical field close to the transition temperature has been revealed. The obtained upturn of the critical field curves as a function of temperature, both in four and five spacetime dimensions, is a fingerprint of the strong coupling approach.

  6. Magnetization Measurements of Hard Superconductors under Dissipative Transport

    Energy Technology Data Exchange (ETDEWEB)

    Giordano, J L [Departamento de Ciencias de la IngenierIa, Universidad de Talca (Chile); Luzuriaga, J [Centro Atomico Bariloche, CNEA, Instituto Balseiro, UNC (Argentina); RuIz-Tagle, I A [Instituto de QuImica de Recursos Naturales, Universidad de Talca (Chile); Nieva, G [Centro Atomico Bariloche, CNEA, Instituto Balseiro, UNC (Argentina); BadIa-Majos, A [Departamento de Fisica de la Materia Condensada-I.C.M.A., Universidad de Zaragoza (Spain)

    2006-06-01

    The hysteretic magnetic flux dynamics of ceramic type-II superconductors under superimposed transport current cycles has been investigated. Field cooled and zero field cooled experiments were carried-out on polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7-x} cylinders by using both temperature and applied field control, to drive the sample into the semi-reversible granular regime. The transport current magnitude was near and above the dissipative threshold. The interplay between shielding and transport due to vortex-pinning interactions, equilibrium magnetization effects, and diamagnetic/paramagnetic relaxation phenomena are shown to play an important role in the range of practical applications.

  7. Magnetic stripes in the UCoGe superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Mora, Pablo de la [Departemento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-542, 04510 Mexico DF, Mexico and Institute de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, Campus Morelia (Mexico); Navarro, O, E-mail: delamora@unam.m [Instituto de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, 04510 Mexico DF (Mexico)

    2009-05-01

    The magnetic superconductor UCoGe is analyzed with an electronic structure package, spin-orbit coupling and intra-atomic repulsion (via Hubbard U{sub H}) were included. The possibility of an antiferromagnetic configuration is studied, but it is found to be unstable, also the non-collinear magnetization seems to be ruled out. The magnetization is given mainly by the Co-atoms with M = 0.6 mu{sub B}/f.u. The U-atoms have two magnetic moments; M = 0.07 and 0.32 mu{sub B}/f.u. arranged in an alternated planes along the b-direction forming magnetic stripes.

  8. Fluctuation conductivity of disordered superconductors in magnetic fields

    Science.gov (United States)

    Tarasinski, Brian; Schwiete, Georg

    2013-07-01

    We calculate fluctuation corrections to the longitudinal conductivity of disordered superconductors subject to an external magnetic field. We derive analytic expressions that are valid in the entire metallic part of the temperature-magnetic field phase diagram as long as the effect of the magnetic field on the spin degrees of freedom of the electrons may be neglected. Our calculations are based on a kinetic equation approach. For the special case of superconducting films and wires in parallel magnetic fields, we perform a detailed comparison with results that were previously obtained with diagrammatic perturbation theory in the imaginary-time formalism. As an application, we study the fluctuation conductivity of films in tilted magnetic fields with a special focus on the low-temperature regime. We present a detailed discussion of the phenomenon of the nonmonotonic magnetoresistance and find that it displays a pronounced dependence on the tilting angle.

  9. Effect of superconductor filament magnetization on the field errors

    CERN Document Server

    Wolf, R

    1999-01-01

    One of the main source of field errors in a superconducting magnet is the magnetization M of the superconducting filaments. Screening currents, of persistent nature, are induced by any. field change during operation of the magnet. This chapter describes the models for the calculation of these effects and the parameters to be defined in ROXIE. (3 refs).

  10. Unconventional superconductors under a rotating magnetic field. II. Thermal transport

    Science.gov (United States)

    Vorontsov, A. B.; Vekhter, I.

    2007-06-01

    We present a microscopic approach to the calculations of thermal conductivity in unconventional superconductors for a wide range of temperatures and magnetic fields. Our work employs the nonequilibrium Keldysh formulation of the quasiclassical theory. We solve the transport equations using a variation of the Brandt-Pesch-Tewordt method that accounts for the quasiparticle scattering on vortices. We focus on the dependence of the thermal conductivity on the direction of the field with the respect to the nodes of the order parameter, and discuss it in the context of experiments aiming to determine the shape of the gap from such anisotropy measurements. We consider quasi-two-dimensional Fermi surfaces with vertical line nodes and use our analysis to establish the location of gap nodes in heavy-fermion CeCoIn5 and the organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 .

  11. Revisiting holographic superconductor with Magnetic Fields

    CERN Document Server

    Momeni, Davood

    2014-01-01

    We study the effect of the bulk magnetic field (charge) on scalar condensation using an analytical approach of matching. An AdS-magnetized black hole solution has been used as a probe solution of normal phase of a strongly coupled condensed matter system on boundary. In the zero temperature limit of the black hole and infinite temperature, we show that there exists a critical magnetic field and so, the Meissner's effect presented. We compare this analytical result with our previous variational approach. By studying the different between heat capacities of the normal and superconducting phases near the critical point, we show that this thermodynamic quantity becomes divergent as the Rutgers formula predicted. Mathematical pole of Rutgers formula gives us a maximum for magnetic field which at this value, the system backs to the normal phase. In zero temperature we investigate exact series solutions of the field equations using an appropriate boundary conditions set. We show that conformal dimension is fixed by ...

  12. Magnetic-flux dynamics of high-Tc superconductors in weak magnetic fields

    DEFF Research Database (Denmark)

    Il’ichev, E. V.; Jacobsen, Claus Schelde

    1994-01-01

    Aspects of magnetic-flux dynamics in different types of samples of the high-temperature superconductor YBa2Cu3Ox have been investigated in magnetic fields below 1 Oe and at 77 K. The experiments were carried out in an arrangement including a field coil, a flat sample perpendicular to the field...

  13. Evaluation of magnetic loss in a YBa sub 2 Cu sub 3 O sub x superconductor

    CERN Document Server

    Konishi, H; Futamura, M

    2003-01-01

    We measured the magnetic force between a YBa sub 2 Cu sub 3 O sub x (YBCO) superconductor and a Nd-Fe-B magnet while reciprocating the superconductor under the magnet. The magnetic force showed a hysteretic characteristic against the displacement of the superconductor. Magnetic loss calculated from the hysteresis curve decreased as the drive frequency increased. A mechanical model was used to analyze the characteristics of the magnetic loss. By adding the contribution of viscous force and repined flux lines to the mechanical model, we obtained good agreement between the analytical and experimental results. (author)

  14. Calculating levitation forces in the magnet-high-temperature superconductor systems

    NARCIS (Netherlands)

    Ermolaev, YS; Rudnev, IA

    2005-01-01

    A new method of calculation of the magnetic levitation force in the permanent magnet-high-temperature superconductor systems is proposed based on the Maxwell equations and the Bean model. The dependences of the levitation force on the gap width calculated for various regimes of superconductor coolin

  15. Calculating levitation forces in the magnet-high-temperature superconductor systems

    NARCIS (Netherlands)

    Ermolaev, YS; Rudnev, IA

    2005-01-01

    A new method of calculation of the magnetic levitation force in the permanent magnet-high-temperature superconductor systems is proposed based on the Maxwell equations and the Bean model. The dependences of the levitation force on the gap width calculated for various regimes of superconductor coolin

  16. Magnetic flux noise in copper oxide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, M.J.

    1991-11-01

    Magnetic flux noise and flux creep in thin films and single crystals of YBa{sub 2}Cu{sub 3}O{sub 7-x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x}, Tl{sub 2}Ca{sub 2}Ba{sub 2}Cu{sub 3}O{sub x}, and TlCa{sub 2}Ba{sub 2}Cu{sub 3}O{sub x} are measured with a superconducting quantum interference device (SQUID). The noise power spectrum generally scales as 1/f (f is frequency) from 1 Hz to 1 kHz, increases with temperature, and decreases in higher-quality films. It is proportional to the magnetic field B in which the sample is cooled, at least in the range 0.1 mT < B < 3 mT. A model of thermally activated vortex motion is developed which explains the dependence of the noise on frequency, temperature, current, and applied magnetic field. The pinning potential is idealized as an ensemble of double wells, each with a different activation energy separating the two states. From the noise measurements, this model yields the distribution of pinning energies in the samples, the vortex hopping distance, the number density of mobile vortices, and the restoring force on a vortex at a typical pinning site. The distribution of pinning energies in YBa{sub 2}Cu{sub 3}O{sub 7-x} shows a broad peak below 0.1 eV. The small ambient magnetic field, and the detection of noise even in the absence of a driving force, insure that the measured pinning energies are characteristic of isolated vortices near thermal equilibrium. The observed vortex density in fields much less than 0.1 mT is too large to be explained by the ambient field, suggesting a mechanism intrinsic to the sample which produces trapped vortices.

  17. Superconductors

    CERN Document Server

    Narlikar, A V

    2014-01-01

    Superconductors is neither about basic aspects of superconductivity nor about its applications, but its mainstay is superconducting materials. Unusual and unconventional features of a large variety of novel superconductors are presented and their technological potential as practical superconductors assessed. The book begins with an introduction to basic aspects of superconductivity. The presentation is readily accessible to readers from a diverse range of scientific and technical disciplines, such as metallurgy, materials science, materials engineering, electronic and device engineering, and chemistry. The derivation of mathematical formulas and equations has been kept to a minimum and, wherever necessary, short appendices with essential mathematics have been added at the end of the text. The book is not meant to serve as an encyclopaedia, describing each and every superconductor that exists, but focuses on important milestones in their exciting development.

  18. Superconducting flux pump for high-temperature superconductor insert coils of NMR magnets

    Science.gov (United States)

    Jeong, S.; Lee, H.; Iwasa, Y.

    2002-05-01

    This paper describes a prototype flux pump recently operated at the MIT Francis Bitter Magnet Laboratory. The results of the prototype flux pump will be used in the development of a full-scale flux pump that will be coupled to a high-temperature superconductor (HTS) insert coil of a high-field NMR magnet. Such an HTS insert is unlikely to operate in persistent mode because of the conductor's low index (n). The flux pump can compensate for field decay in the HTS insert coil and make the insert operate effectively in persistent mode. The flux pump, comprised essentially of a transformer and two switches, all made of superconductor, transfers into the insert coil a fraction of a magnetic energy that is first introduced in the secondary circuit of the transformer by a current supplied to the primary circuit. A prototype flux pump has been designed, fabricated, and operated to demonstrate that a flux pump can indeed supply a small metered current into a load superconducting magnet. A current increment in the range of microamperes has been measured in the magnet after each pumping action. The superconducting prototype flux pump is made of Nb3Sn tape. The pump is placed in a gaseous environment above the liquid helium level to keep its heat dissipation from directly discharged in the liquid; the effluent helium vapor maintains the thermal stability of the flux pump. [This paper is also published in Advances in Cryogenic Engineering Volume 47A, AIP Conference Proceedings Volume 613, pp. 441-448.

  19. Scaling critical behavior of superconductors at zero magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Calan, C. de; Nogueira, F.S. [Ecole Polytechnique (France). Centre de Physique Theorique

    2000-07-01

    Full text follows: We consider the scaling behavior in the critical domain of superconductors at zero external magnetic field. The Josephson's relation for a charged superfluid is proved without assuming the hyperscaling relation. On the other hand we discuss the dual Ginzburg-Landau model. In this dual model, due to the presence of two mass scales, a continuous family of non equivalent scalings can be defined. The relevant critical regimes are identified, and the corresponding critical exponents are predicted. (author)

  20. Vibration effect on magnetization and critical current density of superconductors

    Science.gov (United States)

    Golovchanskiy, Igor A.; Pan, Alexey V.; George, Jonathan; Wells, Frederick S.; Fedoseev, Sergey A.; Rozenfeld, Anatoly

    2016-07-01

    In this work the effect of vibrations on critical current density (J c ) of superconductors has been studied. The vibrations are shown to affect J c of all types of superconductors during their measurements, employing a vibrating sample magnetometer (VSM). Increasing vibration frequency (f) and/or amplitude (A) leads to progressive reduction of J c as a function of magnetic field (B a ). The effect of vibrations is substantially stronger in thin films. It leads to development of unexpected kinks on {J}c({B}a) curves. Analysis of magnetization loops and relaxation of magnetization in YBCO films revealed that the vibration effect can be treated as the effective reduction of pinning potential. The asymmetry of the vibration effect in ascending and descending B a is observed, indicating differences in free energy of the corresponding vortex structures. Thermal effects induced by vibrations with large f and A are shown to have rather insignificant influence, while the vibrational vortex dynamics exhibit a strong impact. The irreversibility field ({B}{{irr}}) is shown to be instrumentally defined, and its value depends on VSM settings. In addition, the practical importance of {B}{{irr}} for J c modeling is demonstrated.

  1. Magnetic flux noise in copper oxide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, Mark Joseph [Univ. of California, Berkeley, CA (United States)

    1991-11-01

    Magnetic flux noise and flux creep in thin films and single crystals of YBa2Cu3O7-x, Bi2Sr2CaCu2O8+x, Tl2Ca2Ba2Cu3Ox, and TlCa2Ba2Cu3Ox are measured with a superconducting quantum interference device (SQUID). The noise power spectrum generally scales as 1/f (f is frequency) from 1 Hz to 1 kHz, increases with temperature, and decreases in higher-quality films. It is proportional to the magnetic field B in which the sample is cooled, at least in the range 0.1 mT < B < 3 mT. A model of thermally activated vortex motion is developed which explains the dependence of the noise on frequency, temperature, current, and applied magnetic field. The pinning potential is idealized as an ensemble of double wells, each with a different activation energy separating the two states. From the noise measurements, this model yields the distribution of pinning energies in the samples, the vortex hopping distance, the number density of mobile vortices, and the restoring force on a vortex at a typical pinning site. The distribution of pinning energies in YBa2Cu3O7-x shows a broad peak below 0.1 eV. The small ambient magnetic field, and the detection of noise even in the absence of a driving force, insure that the measured pinning energies are characteristic of isolated vortices near thermal equilibrium. The observed vortex density in fields much less than 0.1 mT is too large to be explained by the ambient field, suggesting a mechanism intrinsic to the sample which produces trapped vortices.

  2. Flux line depinning in a magnet-superconductor levitation system

    Science.gov (United States)

    Terentiev, A. N.; Hull, J. R.; De Long, L. E.

    The AC loss characteristics of a magnet-superconductor system were studied with the magnet fixed to the free end of an oscillating cantilever located near a stationary melt-textured YBCO pellet. Below a threshold AC field amplitude ≈2 Oe, the dissipation of the oscillator is amplitude-independent, characteristic of a linear, non-hysteretic regime. Above threshold, dissipation increases with amplitude, reflecting the depinning and hysteretic motion of flux lines. The threshold AC field is an order of magnitude higher than that measured for the same YBCO material via AC susceptometry in a uniform DC magnetic field. A partial lock-in of flux lines between YBCO ab planes is proposed as the mechanism for the substantial increase of the depinning threshold.

  3. Superconductors with low critical temperature for electro-magnets

    CERN Document Server

    Devred, Arnaud

    2002-01-01

    Among the superconductors with low critical temperature that are used to build magnets, NbTi has reached a development state that allows a massive production for big equipment of physics and an industrial production in the domain of medicine imaging. The material that might challenge the supremacy of NbTi is Nb sub 3 Sn but some technical difficulties have yet to be overcome. This report begins with a review of the different industrial processes used to produce superconducting wires based on the NbTi and Nb sub 3 Sn materials. The transition from the superconducting state to the resistive normal state is described for both materials, the magnetizing of multi-wire superconducting cables is also presented. The details the different patterns of wires in cables and proposes a formulary that allows the determination, in some simple cases,of energy losses that are generated in a superconducting cable by a variable magnetic field. (A.C.)

  4. The magnetostriction in a superconductor-magnet system under non-uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xueyi; Jiang, Lang; Wu, Hao [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, Lanzhou University, Lanzhou, Gansu 730000 (China); Gao, Zhiwen, E-mail: gaozhw@lzu.edu.cn [Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

    2017-03-15

    Highlights: • We studied firstly magnetostriction in HTS under non-uniform magnetic field. • The superconductors may be homogeneous and nonhomogeneous. • The magnetostrictions response of the HTS is sensitive to the critical current density and amplitude of the applied magnetic field. • The magnetostriction of nonhomogeneous HTS is larger than that of homogeneous HTS. - Abstract: This paper describes a numerical model to examine the magnetostriction of bulk high-temperature superconductor (HTS) under non-uniform magnetic field in conjunction with finite element analysis. Through this model, the magnetostriction of homogeneous and nonhomogeneous HTS can be implemented under non-uniform magnetic field. Further, the effects of critical current density, applied field frequency and amplitude are also considered. The computational study can provide a fundamental mechanistic understanding the effects of non-uniform magnetic field on magnetostriction of HTS.

  5. The AC magnetic susceptibility of high temperature superconductors

    CERN Document Server

    Salim, M

    2001-01-01

    This research concerns the development of AC magnetic susceptometers and use of susceptometers in analysing high temperature superconductors. Two of the designs were a differential magnetic susceptometer (DMS) and a double coil screening susceptometer (DCSS) whose descriptions are given in detail including coil design, field measurements, susceptometer operation, experimental instrumentation, phase adjustment, susceptometer calibration and sensitivity for each design. Theoretical details are given regarding each design in order to calculate the complex external and internal susceptibility. Investigation concerning the demagnetisation factor of different geometries, and the significant features and limitation for each design are also provided. The susceptometers were applied to a wide range of YBCO samples, which includes bulk samples with different geometry (i.e. Slabs, disk, powder and thick film) and thin films with different oxygen contents. Several silver sheathed Bi-2223 tapes were also involved. This al...

  6. Novel behavior of magnetic flux lines in type II superconductors

    Science.gov (United States)

    Mohler, Gregory Allan

    In this thesis we present several studies in the properties of magnetic flux lines in type II superconductors. We have carried out a model calculation of the flux noise produced by vortex avalanches in a Type-II superconductor, using a simple kinetic model proposed by Bassler and Paczuski. Over a broad range of frequencies, we find that the flux noise SFw has a power-law dependence on frequency, SFw ˜ w-s , with s ˜ 1.4 in reasonable agreement with experiment. In addition, for small lattices, the calculated SFw has a high-frequency knee, which is seen in some experiments, and which is due to the finite lattice size. We have analyzed the Lawrence-Doniach free energy in a tilted magnetic field within the lowest Landau level (LLL) approximation for the case of a highly anisotropic high temperature superconductor. The free energy maps onto that of a strictly c-axis field, but with a reduced interlayer coupling. We use this result to calculate the tilt modulus C44 of a vortex lattice and vortex liquid. The vortex contribution to C44 can be expressed in terms of the squared c-axis Josephson plasmon frequency w2pl . We find that the transverse component of the field has very little effect on the position of the melting curve. We present a simple numerical model for the IV characteristics of a highly anisotropic high temperature superconductor in different geometries. An array of grains coupled together by Josephson junctions is used, with a triangular structure in the planes normal to an applied magnetic field and a square structure otherwise. Overdamped junctions are used to describe the CuO2 planes, while underdamped junctions are used to describe the interplanar coupling. Each grain has a capacitive shunt to ground. We measure the depinning current strength, decoupling current strength, and the critical coupling value in the "flux-transformer geometry." We also examine voltage branches in the I--V hysteresis curve for c-axis transport. Finally, we have used a simple

  7. Development of high temperature superconductors for magnetic field applications

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, D.C.

    1991-12-31

    The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbation to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of the HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development.

  8. Development of high temperature superconductors for magnetic field applications

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, D.C.

    1991-01-01

    The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbation to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of the HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development.

  9. Vortex-antivortex nucleation in magnetically nanotextured superconductors: Magnetic-field-driven and thermal scenarios

    OpenAIRE

    Milosevic, M. V; Peeters, F. M.

    2005-01-01

    Within the Ginzburg-Landau formalism, we predict two novel mechanisms of vortex-antivortex nucleation in a magnetically nanostructured superconductor. Although counterintuitive, nucleation of vortex-antivortex pairs can be activated in a superconducting (SC) film covered by arrays of submicron ferromagnets (FMs) when exposed to an external homogeneous magnetic field. In another scenario, we predict the thermal induction of vortex-antivortex configurations in SC/FM samples. This phenomenon lea...

  10. A Cryogenic Magnetostrictive Actuator Using a Persistent High Temperature Superconducting Magnet. Part 1; Concept and Design

    Science.gov (United States)

    Horner, Garnett; Bromberg, Leslie; Teter, J. P.

    2000-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSCCO 2212 with a magnetostrictive element will be discussed.

  11. Magnetic Signals of High-Temperature Superconductor Bulk During the Levitation Force Measurement Process

    Science.gov (United States)

    Huang, Huan; Zheng, Jun; Qian, Nan; Che, Tong; Zheng, Botian; Jin, Liwei; Deng, Zigang

    2017-05-01

    In order to study the commonly neglected magnetic field information in the course of levitation force measurement process in a superconducting maglev system, a multipoint magnetic field measurement platform was employed to acquire magnetic signals of a bulk high-Tc superconductor on both the top and the bottom surface. Working conditions including field cooling (FC) and zero field cooling were investigated for these vertical down and up motions above a permanent magnet guideway performed on a HTS maglev measurement system. We have discussed the magnetic flux variation process based on the Bean model. A magnetic hysteresis effect similar to the levitation force hysteresis loop of the bulk superconductor was displayed and analyzed in this paper. What is more valuable, there exists some available magnetic flux on the top surface of the bulk superconductor, and the proportion is as high as 62.42% in the FC condition, which provides an experimental hint to design the superconductor bulk and the applied field for practical use in a more efficient way. In particular, this work reveals real-time magnetic flux variation of the bulk superconductor in the levitation application, which is the other important information in contrast to the macroscopic levitation and guidance force investigations in previous studies, and it enriches the existing research methods. The results are significant for understanding the magnetic characteristic of superconductors, and they can contribute to optimize the present HTS maglev system design.

  12. Magnetic Signals of High-Temperature Superconductor Bulk During the Levitation Force Measurement Process

    Science.gov (United States)

    Huang, Huan; Zheng, Jun; Qian, Nan; Che, Tong; Zheng, Botian; Jin, Liwei; Deng, Zigang

    2017-02-01

    In order to study the commonly neglected magnetic field information in the course of levitation force measurement process in a superconducting maglev system, a multipoint magnetic field measurement platform was employed to acquire magnetic signals of a bulk high-Tc superconductor on both the top and the bottom surface. Working conditions including field cooling (FC) and zero field cooling were investigated for these vertical down and up motions above a permanent magnet guideway performed on a HTS maglev measurement system. We have discussed the magnetic flux variation process based on the Bean model. A magnetic hysteresis effect similar to the levitation force hysteresis loop of the bulk superconductor was displayed and analyzed in this paper. What is more valuable, there exists some available magnetic flux on the top surface of the bulk superconductor, and the proportion is as high as 62.42% in the FC condition, which provides an experimental hint to design the superconductor bulk and the applied field for practical use in a more efficient way. In particular, this work reveals real-time magnetic flux variation of the bulk superconductor in the levitation application, which is the other important information in contrast to the macroscopic levitation and guidance force investigations in previous studies, and it enriches the existing research methods. The results are significant for understanding the magnetic characteristic of superconductors, and they can contribute to optimize the present HTS maglev system design.

  13. Magnetic field-induced quantum superconductor-insulator transition in $Nb_{0.15}Si_{0.85}$

    OpenAIRE

    Aubin, H.; Marrache-Kikuchi, C. A.; Pourret, A.; Behnia, K.; Berge, L.; Dumoulin, L.; Lesueur, J.

    2006-01-01

    A study of magnetic-field tuned superconductor-insulator transitions in amorphous $Nb_{0.15}Si_{0.85}$ thin films shows that quantum superconductor-insulator transitions are characterized by an unambiguous signature -- a kink in the temperature profile of the critical magnetic field. Using this criterion, we show that the nature of the magnetic-field tuned superconductor-insulator transition depends on the orientation of the field with respect to the film. For perpendicular magnetic field, th...

  14. Magnetic proximity effect at the interface between a cuprate superconductor and an oxide spin valve

    Science.gov (United States)

    Ovsyannikov, G. A.; Demidov, V. V.; Khaydukov, Yu. N.; Mustafa, L.; Constantinian, K. Y.; Kalabukhov, A. V.; Winkler, D.

    2016-04-01

    A heterostructure that consists of the YBa2Cu3O7-δ cuprate superconductor and the SrRuO3/La0.7Sr0.3MnO3 ruthenate/manganite spin valve is investigated using SQUID magnetometry, ferromagnetic resonance, and neutron reflectometry. It is shown that a magnetic moment is induced due to the magnetic proximity effect in the superconducting part of the heterostructure, while the magnetic moment in the composite ferromagnetic interlayer is suppressed. The magnetization emerging in the superconductor coincides in order of magnitude with the results of calculations taking into account the induced magnetic moment of Cu atoms because of orbital reconstruction at the interface between the superconductor and the ferromagnet, as well as with the results of the model taking into account the variations in the density of states at a distance on the order of the coherence length in the superconductor. The experimentally obtained characteristic penetration depth of the magnetic moment in the superconductor considerably exceeds the coherence length of the cuprate superconductor, which indicates the predominance of the mechanism of induced magnetic moment of Cu atoms.

  15. Magnetic irreversibility and zero resistance in granular Y358 superconductor

    Science.gov (United States)

    Dias, F. T.; Oliveira, C. P.; Vieira, V. N.; Silva, D. L.; Mesquita, F.; Almeida, M. L.; Schaf, J.; Pureur, P.

    2014-12-01

    We report on magnetization and magnetoresistance measurements of polycrystalline Y3Ba5Cu8O18 superconductor (Y358), prepared by solid state reaction in order to study the correlation between the magnetic irreversibility line and the zero electric resistance as a function of applied field. The magnetization measurements were performed using a MPMS-XL SQUID magnetometer and the magnetoresistance measurements were made using a PPMS, both from Quantum Design, up to 1 T. The granular microstructure was confirmed by scanning electron microscopy. In this case the grain junctions are weaker than in the Y123 system and the effect of the applied field on the grain couplings is much stronger. Consequently, in our sample the zero resistance line shifts away from the irreversibility line and is lower by more than 15 K at 1 T. We explain our results in terms of the superconducting glass model and in comparison with results obtained in other materials from the YBaCuO family.

  16. Magnetic Fields above the Surface of aSuperconductor with Internal Magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Bluhm, Hendrik; /Stanford U., Phys. Dept. /SLAC, SSRl

    2007-06-26

    The author presents a method for calculating the magnetic fields near a planar surface of a superconductor with a given intrinsic magnetization in the London limit. He computes solutions for various magnetic domain boundary configurations and derives relations between the spectral densities of the magnetization and the resulting field in the vacuum half space, which are useful if the magnetization can be considered as a statistical quantity and its features are too small to be resolved individually. The results are useful for analyzing and designing magnetic scanning experiments. Application to existing data from such experiments on Sr{sub 2}RuO{sub 4} show that a domain wall would have been detectable, but the magnetic field of randomly oriented small domains and small defects may have been smaller than the experimental noise level.

  17. The magnetostriction in a superconductor-magnet system under non-uniform magnetic field

    Science.gov (United States)

    Li, Xueyi; Jiang, Lang; Wu, Hao; Gao, Zhiwen

    2017-03-01

    This paper describes a numerical model to examine the magnetostriction of bulk high-temperature superconductor (HTS) under non-uniform magnetic field in conjunction with finite element analysis. Through this model, the magnetostriction of homogeneous and nonhomogeneous HTS can be implemented under non-uniform magnetic field. Further, the effects of critical current density, applied field frequency and amplitude are also considered. The computational study can provide a fundamental mechanistic understanding the effects of non-uniform magnetic field on magnetostriction of HTS.

  18. Magnetic behavior of dirty multiband superconductors near the upper critical field

    Science.gov (United States)

    Silaev, Mikhail

    2016-06-01

    Magnetic properties of dirty multiband superconductors near the upper critical field are studied. The parameter κ2 characterizing magnetization slope is shown to have a significant temperature variation which is quite sensitive to the pairing interactions and relative strengths of intraband impurity scattering. In contrast to single-band superconductors the increase of κ2 at low temperatures can be arbitrarily large determined by the ratio of maximal and minimal diffusion coefficients in different bands. Temperature dependencies of κ2(T ) in two-band MgB2 and iron-based superconductors are shown to be much more sensitive to the multiband effects than the upper critical field Hc 2(T ) .

  19. Quantum magnetic excitations from stripes in copper oxide superconductors.

    Science.gov (United States)

    Tranquada, J M; Woo, H; Perring, T G; Goka, H; Gu, G D; Xu, G; Fujita, M; Yamada, K

    2004-06-03

    In the copper oxide parent compounds of the high-transition-temperature superconductors the valence electrons are localized--one per copper site--by strong intra-atomic Coulomb repulsion. A symptom of this localization is antiferromagnetism, where the spins of localized electrons alternate between up and down. Superconductivity appears when mobile 'holes' are doped into this insulating state, and it coexists with antiferromagnetic fluctuations. In one approach to describing the coexistence, the holes are believed to self-organize into 'stripes' that alternate with antiferromagnetic (insulating) regions within copper oxide planes, which would necessitate an unconventional mechanism of superconductivity. There is an apparent problem with this picture, however: measurements of magnetic excitations in superconducting YBa2Cu3O6+x near optimum doping are incompatible with the naive expectations for a material with stripes. Here we report neutron scattering measurements on stripe-ordered La1.875Ba0.125CuO4. We show that the measured excitations are, surprisingly, quite similar to those in YBa2Cu3O6+x (refs 9, 10) (that is, the predicted spectrum of magnetic excitations is wrong). We find instead that the observed spectrum can be understood within a stripe model by taking account of quantum excitations. Our results support the concept that stripe correlations are essential to high-transition-temperature superconductivity.

  20. Quantum magnetic excitations from stripes in copper oxide superconductors

    Science.gov (United States)

    Tranquada, J. M.; Woo, H.; Perring, T. G.; Goka, H.; Gu, G. D.; Xu, G.; Fujita, M.; Yamada, K.

    2004-06-01

    In the copper oxide parent compounds of the high-transition-temperature superconductors the valence electrons are localized-one per copper site-by strong intra-atomic Coulomb repulsion. A symptom of this localization is antiferromagnetism, where the spins of localized electrons alternate between up and down. Superconductivity appears when mobile `holes' are doped into this insulating state, and it coexists with antiferromagnetic fluctuations. In one approach to describing the coexistence, the holes are believed to self-organize into `stripes' that alternate with antiferromagnetic (insulating) regions within copper oxide planes, which would necessitate an unconventional mechanism of superconductivity. There is an apparent problem with this picture, however: measurements of magnetic excitations in superconducting YBa2Cu3O6+x near optimum doping are incompatible with the naive expectations for a material with stripes. Here we report neutron scattering measurements on stripe-ordered La1.875Ba0.125CuO4. We show that the measured excitations are, surprisingly, quite similar to those in YBa2Cu3O6+x (refs 9, 10) (that is, the predicted spectrum of magnetic excitations is wrong). We find instead that the observed spectrum can be understood within a stripe model by taking account of quantum excitations. Our results support the concept that stripe correlations are essential to high-transition-temperature superconductivity.

  1. Quantum magnetic excitations from stripes in copper-oxide superconductors

    Science.gov (United States)

    Tranquada, John

    2005-03-01

    Recent inelastic neutron scattering studies show that the magnetic excitation spectra of two well-studied families of cuprate superconductors are much more similar than previously believed. In particular, I will present results we have obtained on La2-xBaxCuO4 (LBCO) with x = 0.125 [1,2]. Using very large single crystals grown at Brookhaven, we were able to measure the magnetic excitations up to 200 meV using the MAPS time-of-flight spectrometer at the ISIS spallation source. While the lowest energy excitations are split incommensurately, these disperse inwards towards the antiferromagnetic wave vector with increasing energy, merging at ˜50 meV. At higher energies the excitations disperse outwards again. There is a significant enhancement of the Q-integrated magnetic scattering near ˜50 meV compared to lower energies, suggestive of quantum correlations and distinct from spin-wave predictions. Many features of the spectrum are quite similar to those found in YBa2Cu3O6.6 [3]. One can qualitatively characterize the results with a universal excitation spectrum, together with a material-dependent spin gap in the superconducting state. It is important to note that the LBCO sample exhibits static stripe order [2], as this has significant implications for the origin of the magnetic excitations in superconducting cuprates. *J. M. Tranquada, H. Woo, T. G. Perring, H. Goka, G. D. Gu, G. Xu, M. Fujita, and K. Yamada, Nature 429, 534 (2004). *M. Fujita, H. Goka, K. Yamada, J. M. Tranquada, and L.-P. Regnault, Phys. Rev. B 70, 104517 (2004). *S. M. Hayden, H. A. Mook, P. C. Dai, T. G. Perring, and F. Dogan, Nature 429, 531 (2004).

  2. Phenomenological approach to spin fluctuations in itinerant magnets and superconductors from ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Ortenzi, Luciano

    2013-10-17

    In this thesis I study the interplay between magnetism and superconductivity in itinerant magnets and superconductors. I do this by applying a semiphenomenological method to four representative compounds. In particular I use the discrepancies (whenever present) between density functional theory (DFT) calculations and the experiments in order to construct phenomenological models which explain the magnetic, superconducting and optical properties of four representative systems. I focus my attention on the superconducting and normal state properties of the recently discovered APt3P superconductors, on superconducting hole-doped CuBiSO, on the optical properties of LaFePO and finally on the ferromagnetic-paramagnetic transition of Ni3Al under pressure. At the end I present a new method which aims to describe the effect of spin fluctuations in itinerant magnets and superconductors that can be used to monitor the evolution of the electronic structure from non magnetic to magnetic in systems close to a quantum critical point.

  3. Levitation forces of a bulk YBCO superconductor in gradient varying magnetic fields

    Science.gov (United States)

    Jiang, J.; Gong, Y. M.; Wang, G.; Zhou, D. J.; Zhao, L. F.; Zhang, Y.; Zhao, Y.

    2015-09-01

    The levitation forces of a bulk YBCO superconductor in gradient varying high and low magnetic fields generated from a superconducting magnet were investigated. The magnetic field intensity of the superconducting magnet was measured when the exciting current was 90 A. The magnetic field gradient and magnetic force field were both calculated. The YBCO bulk was cooled by liquid nitrogen in field-cooling (FC) and zero-field-cooling (ZFC) condition. The results showed that the levitation forces increased with increasing the magnetic field intensity. Moreover, the levitation forces were more dependent on magnetic field gradient and magnetic force field than magnetic field intensity.

  4. Measuring the interaction force between a high temperature superconductor and a permanent magnet

    OpenAIRE

    Valenzuela, S. O.; Jorge, G. A.; Rodriguez, E.

    1999-01-01

    Repulsive and attractive forces are both possible between a superconducting sample and a permanent magnet, and they can give place to magnetic levitation or free-suspension phenomena, respectively. We show experiments to quantify this magnetic interaction which represents a promising field regarding to short-term technological applications of high temperature superconductors. The measuring technique employs an electronic balance and a rare-earth magnet that induces a magnetic moment in a melt...

  5. Surface barrier effect on magnetization of a current-carrying type-II superconductor

    Science.gov (United States)

    Genenko, Yu. A.; Freyhardt, H. C.

    2000-10-01

    Vortex penetration in and exit from ideal flux-filled current-carrying superconductors are studied in the frame of the modified Meissner state model accounting for the vortex interactions with the sample surface, transport current, external field and the other vortices inside the sample. The generalized Silsbee's rule is first formulated and the M- H diagram of ideal current-carrying superconductors in a parallel field is estimated which is irreversible due to the surface effect alone. In general, magnetic behaviour of superconductors is shown to be more reversible in the presence of a transport current.

  6. Photoemission and magnetic response in the bipolaronic superconductor

    CERN Document Server

    Dent, C

    2001-01-01

    in the cuprates is extended to explain the crossing point in the curves of induced magnetization divided by the square root of field against temperature in the less anisotropic cuprates. This model has already been shown to provide a parameter-free expression for T sub c in a wide range of cuprates. We compare our results with experiment in YBa sub 2 Cu sub 3 O sub 7 sub - subdelta. A theory of angle-resolved photoemission (ARPES) in doped charge-transfer Mott insulators is developed taking into account the realistic band structure, (bi)polaron formation due to the strong electron-phonon interaction, and a random field potential. We derive the coherent part of the ARPES spectra with the oxygen hole spectral function calculated in the non-crossing (ladder) approximation and with the exact spectral function of a one-dimensional hole in a random potential. On the basis of this theory, explanations are proposed for several features of the ARPES spectra taken from the cuprate superconductors. These include the pol...

  7. Interplay between superconductivity and magnetism in iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chubukov, Andrey V [University of Wisconsin

    2015-06-10

    This proposal is for theoretical work on strongly correlated electron systems, which are at the center of experimental and theoretical activities in condensed-matter physics. The interest to this field is driven fascinating variety of observed effects, universality of underlying theoretical ideas, and practical applications. I propose to do research on Iron-based superconductors (FeSCs), which currently attract high attention in the physics community. My goal is to understand superconductivity and magnetism in these materials at various dopings, the interplay between the two, and the physics in the phase in which magnetism and superconductivity co-exist. A related goal is to understand the origin of the observed pseudogap-like behavior in the normal state. My research explores the idea that superconductivity is of electronic origin and is caused by the exchange of spin-fluctuations, enhanced due to close proximity to antiferromagnetism. The multi-orbital/multi-band nature of FeSCs opens routes for qualitatively new superconducting states, particularly the ones which break time-reversal symmetry. By all accounts, the coupling in pnictdes is below the threshold for Mott physics and I intend to analyze these systems within the itinerant approach. My plan is to do research in two stages. I first plan to address several problems within weak-coupling approach. Among them: (i) what sets stripe magnetic order at small doping, (ii) is there a preemptive instability into a spin-nematic state, and how stripe order affects fermions; (iii) is there a co-existence between magnetism and superconductivity and what are the system properties in the co-existence state; (iv) how superconductivity emerges despite strong Coulomb repulsion and can the gap be s-wave but with nodes along electron FSs, (v) are there complex superconducting states, like s+id, which break time reversal symmetry. My second goal is to go beyond weak coupling and derive spin-mediated, dynamic interaction between

  8. Endorectal magnetic resonance imaging in persistent hemospermia

    Directory of Open Access Journals (Sweden)

    Adilson Prando

    2008-03-01

    Full Text Available OBJECTIVE: To present the spectrum of abnormalities found at endorectal magnetic resonance imaging (E-MRI, in patients with persistent hemospermia. MATERIALS AND METHODS: A review of E-MRI findings observed in 86 patients with persistent hemospermia was performed and results compared with those reported in the literature. Follow-up was possible in 37 of 86 (43% patients with hemospermia. RESULTS: E-MRI showed abnormal findings in 52 of 86 (60% patients with hemospermia. These findings were: a hemorrhagic seminal vesicle and ejaculatory duct, isolated (n = 11 or 21% or associated with complicated midline prostatic cyst (n = 10 or 19.0%; b hemorrhagic chronic seminal vesiculitis, isolated (n = 14 or 27% or associated with calculi within dilated ejaculatory ducts (n = 2 or 4 %; c hemorrhagic seminal vesicle associated with calculi within dilated ejaculatory duct (n = 4 or 7.7% or within seminal vesicle (n = 4 or 7.7%; d non-complicated midline prostatic cyst (n = 6 or 11.5%; and e prostate cancer (n = 1 or 2%. Successful treatment was more frequent in patients with chronic inflammatory and/or obstructive abnormalities. CONCLUSION: E-MRI should be considered the modality of choice, for the evaluation of patients with persistent hemospermia.

  9. Endorectal magnetic resonance imaging in persistent hemospermia

    Energy Technology Data Exchange (ETDEWEB)

    Prando, Adilson [Vera Cruz Hospital, Campinas, SP (Brazil). Dept. of Radiology and Diagnostic Imaging

    2008-03-15

    Objective: To present the spectrum of abnormalities found at endorectal magnetic resonance imaging (E-MRI), in patients with persistent hemospermia. Materials and methods: A review of E-MRI findings observed in 86 patients with persistent hemospermia was performed and results compared with those reported in the literature. Follow-up was possible in 37 of 86 (43%) patients with hemospermia. Results: E-MRI showed abnormal findings in 52 of 86 (60%) patients with hemospermia. These findings were: a) hemorrhagic seminal vesicle and ejaculatory duct, isolated (n = 11 or 21%) or associated with complicated midline prostatic cyst (n = 10 or 19.0%); b) hemorrhagic chronic seminal vesiculitis, isolated (n = 14 or 27%) or associated with calculi within dilated ejaculatory ducts (n = 2 or 4 %); c) hemorrhagic seminal vesicle associated with calculi within dilated ejaculatory duct (n = 4 or 7.7%) or within seminal vesicle (n = 4 or 7.7%); d) non-complicated midline prostatic cyst (n = 6 or 11.5%); and e) prostate cancer (n = 1 or 2%). Successful treatment was more frequent in patients with chronic inflammatory and/or obstructive abnormalities. Conclusion: E-MRI should be considered the modality of choice, for the evaluation of patients with persistent hemospermia. (author)

  10. Magneto-optical studies of magnetization processes in high-Tc superconductors structure.

    Energy Technology Data Exchange (ETDEWEB)

    Vlasko-Vlasox, V. K.

    1998-12-02

    Magneto-optical imaging is a powerful tool for nondestructive quality control and scientific research through visualization of magnetic fields around any magnetic flux or current carrying sample. It allows real time observations of domain structures and their transformations in magnetics, static and dynamic field patterns due to inhomogeneous currents in electric circuits and superconductors, and reveals distortions of the fields due to defects. In addition to qualitative pictures showing different details in the intensities of the magneto-optical images, one can obtain quantitative maps of field distributions and retrieve values of the underlying currents or magnetization variations. In this review we discuss the advantages of magneto-optics for studies of superconductors, show its place among other techniques, and report recent results in magneto-optical investigations of high temperature superconductors (HTS).

  11. Anisotropic critical magnetic fluctuations in the ferromagnetic superconductor UCoGe

    Science.gov (United States)

    Stock, C.; Sokolov, D. A.; Bourges, P.; Tobash, P. H.; Gofryk, K.; Ronning, F.; Bauer, E. D.; Rule, K. C.; Huxley, A. D.

    2011-09-01

    We report neutron scattering measurements of critical magnetic excitations in the weakly ferromagnetic superconductor UCoGe. The strong non-Landau damping of the excitations we observe, although unusual has been found in another related ferromagnet, UGe2 at zero pressure. However, we also find there is a significant anisotropy of the magnetic correlation length in UCoGe that contrasts with an almost isotropic length for UGe2. The values of the magnetic correlation length and damping are found to be compatible with superconductivity on small Fermi surface pockets. The anisotropy may be important to explain why UCoGe is a superconductor at zero pressure while UGe2 is not.

  12. Thermo-electromagnetic properties of a magnetically shielded superconductor strip: theoretical foundations and numerical simulations

    Science.gov (United States)

    Ma, G. T.; Rauh, H.

    2013-10-01

    Numerical simulations of thermo-electromagnetic properties of a thin type-II superconductor strip surrounded by open cavity soft-magnetic shields and exposed to an oscillating transverse magnetic field are performed by resorting to the quasistatic approximation of a vector potential approach in conjunction with the classical description of conduction of heat. The underlying definition of the superconducting constituent makes use of an extended ‘smoothed’ Bean model of the critical state, which includes the field and temperature dependence of the induced supercurrent as well. The delineation of the magnetic shields exploits the reversible-paramagnet approximation in the Langevin form, as appropriate for magnetizations with narrow Z-type loops, and considers induced eddy currents too. The coolant is envisaged as acting like a bath that instantly takes away surplus heat. Based on the Jacobian-free Newton-Krylov approach and the backward Euler scheme, the numerical analysis at hand is tailored to the problem of a high width/thickness aspect ratio of the superconductor strip. Assigning representative materials characteristics and conditions of the applied magnetic field, the main findings for a practically relevant magnet configuration include: (i) an overall rise of the maximum temperature of the superconductor strip tending to saturation in a superconducting thermo-electromagnetic steady state above the operating temperature, magnetic shielding lending increased stability and smoothing the temperature profile along the width of the superconductor strip; (ii) a washing out of the profile of the magnetic induction and a lowering of its strength, a relaxation of the profile of the supercurrent density and an increase of its strength, a tightening of the power loss density and a reduction of its strength, all inside the superconductor strip. The hysteretic ac loss suffered by the superconductor strip is seen to be cut back or, at most, to converge on that of an

  13. Stable levitation of steel rotors using permanent magnets and high-temperature superconductors

    Science.gov (United States)

    Hull, J. R.; Passmore, J. L.; Mulcahy, T. M.; Rossing, T. D.

    1994-07-01

    Individual freely spinning magnetic steel rotors were levitated by combining the attractive force between permanent magnets and the rotor with the repulsive force between high-temperature superconductors and the steel. The levitation force and stiffness of several configurations are presented, and the application of this levitation method to high-speed bearings is discussed.

  14. Bogomolnyi-type bounds in unconventional superconductors without external magnetic fields

    NARCIS (Netherlands)

    Achucarro, A; Manes, JL

    1996-01-01

    Following Bogomolnyi's classical. treatment of vortices, we develop a method for finding rigorous lower bounds to the Landau-Ginzburg free energy, describing unconventional superconductors in the absence of external magnetic fields. This allows a more precise description of the magnetic instabilitie

  15. Peculiar long-range supercurrent in superconductor-ferromagnet-superconductor junction containing a noncollinear magnetic domain in the ferromagnetic region

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Hao, E-mail: menghao1982@shu.edu.cn [School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001 (China); National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Wu, Xiuqiang [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Ren, Yajie [School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001 (China)

    2015-01-14

    We study the supercurrent in clean superconductor-ferromagnet-superconductor heterostructure containing a noncollinear magnetic domain in the ferromagnetic region. It is demonstrated that the magnetic domain can lead to a spin-flip scattering process, which reverses the spin orientations of the singlet Cooper pair and simultaneously changes the sign of the corresponding electronic momentum. If the ferromagnetic layers on both sides of magnetic domain have the same features, the long-range proximity effect will take place. That is because the singlet Cooper pair will create an exact phase-cancellation effect and gets an additional π phase shift as it passes through the entire ferromagnetic region. Then, the equal spin triplet pair only exists in the magnetic domain region and can not diffuse into the other two ferromagnetic layers. So, the supercurrent mostly arises from the singlet Cooper pairs, and the equal spin triplet pairs are not involved. This result can provide a approach for generating the long-range supercurrent.

  16. Effects of magnetic field on the cuprate high-Tc superconductor La2-xSrxCuO4

    DEFF Research Database (Denmark)

    Lake, B.; Aeppli, G.; Christensen, N.B.

    2004-01-01

    This article discusses neutron scattering measurements on the cuprate, high transition temperature superconductor La2-xSrxCuO4 (LSCO) in an applied magnetic field. LSCO is a type-II superconductor and magnetic flux can penetrate the material via the formation of vorticies. Phase coherent...

  17. Critical Current Test of Liquid Hydrogen Cooled HTC Superconductors under External Magnetic Field

    Science.gov (United States)

    Shirai, Yasuyuki; Shiotsu, Masahiro; Tatsumoto, Hideki; Kobayashi, Hiroaki; Naruo, Yoshihiro; Nonaka, Satoshi; Inatani, Yoshifumi

    High-Tc (HTC) superconductors including MgB2 will show excellent properties under temperature of Liquid Hydrogen (LH2:20K), which has large latent heat and low viscosity coefficient. In order to design and fabricate the LH2 cooled superconducting energy devices, we must clear the cooling property of LH2 for superconductors, the cooling system and safety design of LH2 cooled superconducting devices and electro-magnetic property evaluation of superconductors (BSCCO, REBCO and MgB2) and their magnets cooled by LH2. As the first step of the study, an experimental setup which can be used for investigating heat transfer characteristics of LH2 in a pool and also in forced flow (circulation loop with a pump), and also for evaluation of electro-magnetic properties of LH2 cooled superconductors under external magnetic field (up to 7 T). In this paper, we will show a short sketch of the experimental set-up, practical experiences in safety operation of liquid hydrogen cooling system and example test results of critical current evaluation of HTC superconductors cooled by LH2.

  18. Vortex and characteristics of prestrained type-II deformable superconductors under magnetic fields

    Science.gov (United States)

    Ma, Zeling; Wang, Xingzhe; Zhou, Youhe

    2016-04-01

    Based on the time-dependent Ginzburg-Landau (TDGL) theory and the linear deformation theory, we present a numerical investigation of magnetic vortex characteristics of a type-II deformable superconductor with prestrain. The effect of prestrain on the wave function, vortex dynamics and energy density of a superconducting film is analyzed by solving the nonlinear TDGL equations in the presence of magnetic field. The results show that the prestrain has a remarkable influence on the magnetic vortex distribution and the vortex dynamics, as well as value of wave function of the superconductor. The different prestrains, i.e., pre-given compression and tension strains, result in dissimilar characteristics on a half-plane of deformable superconductor in an applied magnetic field, and the vortex distribution and entrance in a two dimensional superconducting film. The studies demonstrated that the compression prestrain may speed up the vortexes entering into the region of the superconducting film and increases the vortex number in comparison with those of free-prestrain case, while the tension prestrain shows the reversal features. The energy density and spectrum in the superconductor are further demonstrated numerically and discussed. The present investigation is an attempt to give insight into the superconductivity and electromagnetic characteristics taking into account the elastic deformation in superconductors.

  19. Collective magnetic excitations of C4-symmetric magnetic states in iron-based superconductors

    Science.gov (United States)

    Scherer, Daniel D.; Eremin, Ilya; Andersen, Brian M.

    2016-11-01

    We study the collective magnetic excitations of the recently discovered C4-symmetric spin-density-wave states of iron-based superconductors with particular emphasis on their orbital character based on an itinerant multiorbital approach. This is important since the C4-symmetric spin-density-wave states exist only at moderate interaction strengths where damping effects from a coupling to the continuum of particle-hole excitations strongly modify the shape of the excitation spectra compared to predictions based on a local moment picture. We uncover a distinct orbital polarization inherent to magnetic excitations in C4-symmetric states, which provide a route to identify the different commensurate magnetic states appearing in the continuously updated phase diagram of the iron-pnictide family.

  20. A superconducting conveyer system using multiple bulk Y-Ba-Cu-O superconductors and permanent magnets

    Science.gov (United States)

    Kinoshita, T.; Koshizuka, N.; Nagashima, K.; Murakami, M.

    Developments of non-contact superconducting devices like superconducting magnetic levitation transfer and superconducting flywheel energy storage system have been performed based on the interactions between bulk Y-Ba-Cu-O superconductors and permanent magnets, in that the superconductors can stably be levitated without any active control. The performances of noncontact superconducting devices are dependent on the interaction forces like attractive forces and stiffness. In the present study, we constructed a non-contact conveyer for which the guide rails were prepared by attaching many Fe-Nd-B magnets onto an iron base plate. Along the translational direction, all the magnets were arranged as to face the same pole, and furthermore their inter-distance was made as small as possible. The guide rail has three magnet rows, for which the magnets were glued on the iron plate such that adjacent magnet rows have opposite poles like NSN. At the center row, the magnetic field at zero gap reached 0.61T, while the field strengths of two rows on the side edges were only 0.48T due to magnetic interactions among permanent magnets. We then prepared a cryogenic box made with FRP that can store several bulk Y-Ba-Cu-O superconductors 25 mm in diameter cooled by liquid nitrogen. It was found that the levitation forces and stiffness increased with increasing the number of bulk superconductors installed in the box, although the levitation force per unit bulk were almost the same. We also confirmed that these forces are dependent on the configuration of bulk superconductors.

  1. Development of superconducting magnetic bearing with superconducting coil and bulk superconductor for flywheel energy storage system

    Science.gov (United States)

    Arai, Y.; Seino, H.; Yoshizawa, K.; Nagashima, K.

    2013-11-01

    We have been developing superconducting magnetic bearing for flywheel energy storage system to be applied to the railway system. The bearing consists of a superconducting coil as a stator and bulk superconductors as a rotor. A flywheel disk connected to the bulk superconductors is suspended contactless by superconducting magnetic bearings (SMBs). We have manufactured a small scale device equipped with the SMB. The flywheel was rotated contactless over 2000 rpm which was a frequency between its rigid body mode and elastic mode. The feasibility of this SMB structure was demonstrated.

  2. Magnetic response of holographic Lifshitz superconductors:Vortex and Droplet solutions

    CERN Document Server

    Lala, Arindam

    2014-01-01

    In this paper a holographic model of $s$-wave superconductor with anisotropic Lifshitz scaling has been considered. In the presence of an external magnetic field our holographic model exhibits both vortex and droplet solutions. Based on analytic methods we have shown that the anisotropy has no effects on the vortex and droplet solutions whereas it may affect the condensation. Our vortex solution closely resembles with the Ginzburg-Landau theory and a relation between the upper critical magnetic field and superconducting coherence length has been speculated from this comparison. Using Sturm-Liouville method the effects of anisotropy on the critical parameters in insulator/superconductor phase transitions has been analyzed.

  3. Effect of metal impregnation in the field cool magnetization of bulk superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kita, M. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)]. E-mail: kita@istec.or.jp; Nariki, S. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Sakai, N. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Hirabayashi, I. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)

    2006-10-01

    Gd-Ba-Cu-O bulk superconductors have significant potential for various applications due to the high critical current density and the highly trapped magnetic fields. Recently we have developed a large sized bulk superconductor using Gd210, which is discovered in the microgravity experiment. We investigated the mechanical properties and the cryostability of the Gd-Ba-Cu-O bulk superconductor to determine how to improve toughness and heat conduction of the large sized bulk superconductor. We introduced a stainless ring around the circumference of the bulk to increase the fracture strength of the bulk. Also, we introduced Al wires inserted in the hole along the c-axis of the bulk, and then the sample was subjected to the impregnation by using Bi-Sn-Cd alloy. We measured the trapped magnetic fields and the repulsive forces of the samples. The trapped magnetic field distributions were 1.13-1.36 T. The repulsive forces at 1 mm gap between the sample bulk and the permanent magnet with the surface magnetic induction of 0.37 T were about 70 N at 77 K. We have also measured the temperature dependence of the trapped magnetic field, and confirmed the effect of metal impregnation.

  4. Measuring the interaction force between a high temperature superconductor and a permanent magnet

    Science.gov (United States)

    Valenzuela, S. O.; Jorge, G. A.; Rodríguez, E.

    1999-11-01

    Repulsive and attractive forces are both possible between a superconducting sample and a permanent magnet, and they can give rise to magnetic levitation or free-suspension phenomena, respectively. We show experiments to quantify this magnetic interaction, which represents a promising field with regard to short-term technological applications of high temperature superconductors. The measuring technique employs an electronic balance and a rare-earth magnet that induces a magnetic moment in a melt-textured YBa2Cu3O7 superconductor immersed in liquid nitrogen. The simple design of the experiments allows a fast and easy implementation in the advanced physics laboratory with a minimum cost. Actual levitation and suspension demonstrations can be done simultaneously as a help to interpret magnetic force measurements.

  5. Magnetism and Superconductivity in Iron-based Superconductors as Probed by Nuclear Magnetic Resonance

    CERN Document Server

    Hammerath, Franziska

    2012-01-01

    Nuclear Magnetic Resonance (NMR) has been a fundamental player in the studies of superconducting materials for many decades. This local probe technique allows for the study of the static electronic properties as well as of the low energy excitations of the electrons in the normal and the superconducting state. On that account it has also been widely applied to Fe-based superconductors from the very beginning of their discovery in February 2008. This dissertation comprises some of these very first NMR results, reflecting the unconventional nature of superconductivity and its strong link to magnetism in the investigated compounds LaO1–xFxFeAs and LiFeAs.

  6. A star role for stripes[Charge order in high-temperature superconductors in magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada, John [Physics Department, Brookhaven National Laboratory (United States)

    2002-06-01

    New images of magnetic and charge order in copper-oxide compounds are providing important clues about the nature of high-temperature superconductors. Visual images can have a powerful impact on the viewer, and this is certainly the case when the images are atomic-scale pictures of the surface of a high-temperature copper-oxide superconductor. The unusual properties of these materials have vexed condensed-matter theorists for the last 15 years. Now a new flurry of theoretical papers has been stimulated by the latest images of a cuprate superconductor, which reveal that an applied magnetic field can induce 'stripes' of charge. The experimental results provide intriguing and important clues to the nature of these ever-surprising materials - although the theorists have still to agree on their meaning. (U.K.)

  7. Manipulation of magnetic carriers for drug delivery using pulsed-current high T {sub c} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Yung [Energy Technology Division and Material Science Division, Building 335, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)]. E-mail: yscha@anl.gov; Chen, Lihua [Energy Technology Division and Material Science Division, Building 335, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824 (United States); Askew, Thomas [Energy Technology Division and Material Science Division, Building 335, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Physics Department, Kalamazoo College, Kalamazoo, MI 49006 (United States); Veal, Boyd [Energy Technology Division and Material Science Division, Building 335, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Hull, John [Energy Technology Division and Material Science Division, Building 335, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2007-04-15

    An innovative method of manipulating magnetic carriers is proposed, and its feasibility for drug delivery and therapy is demonstrated experimentally. The proposed method employs pulsed-field solenoid coils with high-critical- temperature (T {sub c}) superconductor inserts. Pulsed current is used to magnetize and de-magnetize the superconductor insert. The proposed method was demonstrated to be able to (1) move magnetic particles, ranging in size from a few millimeters to 10 {mu}m, with strong enough forces over a substantial distance, (2) hold the particles at a designated position as long as needed, and (3) reverse the processes and retrieve the particles. We further demonstrated that magnetic particles can be manipulated in a stationary environment, in water flow, and in simulated blood (water/glycerol mixture) flow.

  8. Manipulation of magnetic carriers for drug delivery using pulsed-current high Tc superconductors

    Science.gov (United States)

    Cha, Yung; Chen, Lihua; Askew, Thomas; Veal, Boyd; Hull, John

    2007-04-01

    An innovative method of manipulating magnetic carriers is proposed, and its feasibility for drug delivery and therapy is demonstrated experimentally. The proposed method employs pulsed-field solenoid coils with high-critical- temperature ( Tc) superconductor inserts. Pulsed current is used to magnetize and de-magnetize the superconductor insert. The proposed method was demonstrated to be able to (1) move magnetic particles, ranging in size from a few millimeters to 10 μm, with strong enough forces over a substantial distance, (2) hold the particles at a designated position as long as needed, and (3) reverse the processes and retrieve the particles. We further demonstrated that magnetic particles can be manipulated in a stationary environment, in water flow, and in simulated blood (water/glycerol mixture) flow.

  9. Amplitude and frequency dependence of hysteresis loss in a magnet-superconductor levitation system

    Science.gov (United States)

    Yang, Z. J.; Hull, J. R.; Mulcahy, T. M.; Rossing, T. D.

    1995-08-01

    Using an electromagnetically controlled mechanical pendulum, we measured the energy loss for different amplitudes in a magnetic levitation system that contained high temperature superconductors (HTSs). Two procedures were followed to measure losses at 77 K for frequencies of 93.8 mHz to 80 Hz. In the first procedure, the distance between the permanent magnet and the HTS levitator was the same as that during (field) cooling. In the second procedure, the magnet was lowered (after cooling) closer to the HTS levitator before the measurements were performed. The experimental data show that these two procedures give essentially the same results at the same distance despite different cooling (and magnetization) histories for melt-textured YBaCuO levitators, and the frequency-independent energy loss is a power-law function of amplitude. We attribute the energy loss to magnetic hysteresis in the superconductor.

  10. Superconductor-Magnet Bearings With Inherent Stability and Velocity-Independent Drag Torque

    Science.gov (United States)

    Lee, Eun-Jeong; Ma, Ki Bui; Wilson, Thomas L.; Chu, Wei-Kan

    1999-01-01

    A hybrid superconductor magnet bearing system has been developed based on passive magnetic levitation and the flux pinning effect of high-temperature superconductivity. The rationale lies in the unique capability of a high-temperature superconductor (HTS) to enhance system stability passively without power consumption. Characterization experiments have been conducted to understand its dynamic behavior and to estimate the required motor torque for its driving system design. These experiments show that the hybrid HTS-magnet bearing system has a periodic oscillation of drag torque due mainly to the nonuniform magnetic field density of permanent magnets. Furthermore, such a system also suffers from a small superimposed periodic oscillation introduced by the use of multiple HTS disks rather than a uniform annulus of HTS material. The magnitude of drag torque is velocity independent and very small. These results make this bearing system appealing for high-speed application. Finally, design guidelines for superconducting bearing systems are suggested based on these experimental results.

  11. Maximum trapped field of a ring bulk superconductor by low pulsed field magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchimoto, M. [Hokkaido Institute of Technology, 7-15 Maeda, Teine-ku, Sapporo 006-8585 (Japan)], E-mail: tsuchi@hit.ac.jp; Kamijo, H. [Railway Technical Research Institute, 2-8-38, Hikari-cho, Kokubunji, Tokyo 185-8540 (Japan)

    2007-10-01

    Pulsed field magnetization is an important technique for a bulk superconducting magnet, which is one practical application of a bulk high T{sub c} superconductor (HTS). Full magnetization of a ring HTS is effective to obtain large trapped field for low pulsed field magnetization. In this study, trapped field in a ring bulk superconductor by the low pulsed field magnetization is numerically analyzed under assumption of variable shielding current by the temperature control. Differences between one-dimensional Bean model and axisymmetric three-dimensional numerical solution are discussed through the analysis. There is maximum trapped field in the axisymmetric three-dimensional model because of finite thickness of the ring HTS. The shielding current density and inner radius of the ring HTS are discussed to obtain the maximum trapped field.

  12. Majorana edge states in superconductor-noncollinear magnet interfaces

    Science.gov (United States)

    Chen, Wei; Schnyder, Andreas P.

    2015-12-01

    Through s -d coupling, a superconducting thin film interfaced to a noncollinear magnetic insulator inherits its magnetic order, which may induce unconventional superconductivity that hosts Majorana edge states. We present a unified formalism that covers the cycloidal, helical, and tilted conical order discovered in multiferroics, as well as Bloch and Neel domain walls of ferromagnetic insulators, and show that they induce (px+py )-wave pairing that supports Majorana edge modes. The advantages over one-dimensional proposals are that the Majorana states can exist without fine tuning of the chemical potential, can be stabilized in a much larger parameter space, and can be separated over the distance of long-range noncollinear order that is known to reach a macroscopic scale. A skyrmion spin texture, on the other hand, induces a nonuniform (pr+i pφ )-wave-like pairing under the influence of an emergent electromagnetic field, yielding a vortex state that displays both a bulk persistent current and a topological edge current.

  13. Investigation on stresses of superconductors under pulsed magnetic fields based on multiphysics model

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaobin, E-mail: yangxb@lzu.edu.cn; Li, Xiuhong; He, Yafeng; Wang, Xiaojun; Xu, Bo

    2017-04-15

    Highlights: • The differential equation including temperature and magnetic field was derived for a long cylindrical superconductor. • Thermal stress and electromagnetic stress were studied at the same time under pulse field magnetizing. • The distributions of the magnetic field, the temperature and stresses are studied and compared for two pulse fields of the different duration. • The Role thermal stress and electromagnetic stress play in the process of pulse field magnetizing is discussed. - Abstract: A multiphysics model for the numerical computation of stresses, trapped field and temperature distribution of a infinite long superconducting cylinder is proposed, based on which the stresses, including the thermal stresses and mechanical stresses due to Lorentz force, and trapped fields in the superconductor subjected to pulsed magnetic fields are analyzed. By comparing the results under pulsed magnetic fields with different pulse durations, it is found that the both the mechanical stress due to the electromagnetic force and the thermal stress due to temperature gradient contribute to the total stress level in the superconductor. For pulsed magnetic field with short durations, the thermal stress is the dominant contribution to the total stress, because the heat generated by AC-loss builds up significant temperature gradient in such short durations. However, for a pulsed field with a long duration the gradient of temperature and flux, as well as the maximal tensile stress, are much smaller. And the results of this paper is meaningful for the design and manufacture of superconducting permanent magnets.

  14. Nuclear magnetic resonance in atomic-scale superconductor/magnet multilayered systems

    CERN Document Server

    Kanegae, Y

    2003-01-01

    We investigate the nuclear spin-lattice relaxation rate (T sub 1 T) sup - sup 1 in atomic-scale superconductor/magnet multilayered systems and discuss the discrepancy between two recent (T sub 1 T) sup - sup 1 experiments on Ru in RuSr sub 2 YCu sub 2 O sub 8. When the magnetic layers is are in the antiferromagnetic state, (T sub 1 T) sup - sup 1 in the magnetic layers is shown to decrease with decreasing due to the excitation gap associated with the magnetic ordering. The proximity effect of superconductivity on (T sub 1 T) sup - sup 1 in the magnetic layer is negligibly small. Our result indicates that the temperature dependence of (T sub 1 T) sup - sup 1 on Ru in RuSr sub 2 YCu sub 2 O sub 8 likely originates from the antiferromagnetism in the RuO sub 2 layers, but not from the superconductivity in the CuO sub 2 layers. (author)

  15. Study of the itinerant electron magnetism of Fe-based superconductors by the proximity effect

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Yu.N., E-mail: chiang@ilt.kharkov.ua [B. I. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin ave., Kharkov 61103 (Ukraine); Chareev, D.A. [Lomonosov Moscow State University, GSP-1, Leninskie Gorky, Moscow 119991 (Russian Federation); Dzuba, M.O.; Shevchenko, O.G. [B. I. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin ave., Kharkov 61103 (Ukraine); Vasiliev, A.N. [Lomonosov Moscow State University, GSP-1, Leninskie Gorky, Moscow 119991 (Russian Federation)

    2013-12-15

    Highlights: •We study electron transport through NS boundary in the interior of FeSe and LaO(F)FeAs. •Spin polarization of electron transport is observed. •It is proved that in this case Andreev conductance is sensitive to spin rotation symmetry. •Hysteresis of magnetoresistance also confirms the spin polarization of charge carriers. •We suggest that superconductivity in the systems is connected with itinerant magnetism. -- Abstract: We offer a unconventional method for the study of superconductors using own magnetic field of the transport current as a tool to achieve an ideal (”barrier-free”) NS boundary inside the superconductor due to the proximity effect. Since the probability of Andreev reflection at such a boundary is of order of 1, it is possible with the same probability to judge the nature of phenomena accompanying the conversion of the dissipative current in the supercurrent at it. Thus, in systems with NS boundaries inside unconventional superconductors, monocrystalline chalcogenide FeSe and granulated pnictides LaO(F)FeAs, we have direct evidence of spin-polarized nature of transport and the absence of residual magnetization in their ground normal state: In heterocontacts with these superconductors we detected the spin-dependent contribution to the efficiency of the Andreev reflection associated with the spin accumulation at the NS boundary, and a hysteresis of FeSe conductivity in the ground normal state in low external magnetic fields. Based on our findings, we conclude that in iron-based superconductors, the itinerant electron magnetism is predominant, magnetism of iron atoms being localized.

  16. High-resolution dichroic imaging of magnetic flux distributions in superconductors with scanning x-ray microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ruoss, Stephen; Stahl, Claudia; Weigand, Markus; Schuetz, Gisela [Max-Planck-Institut fuer Intelligente Systeme, Stuttgart (Germany); Albrecht, Joachim [Research Institute for Innovative Surfaces, FINO, Aalen University (Germany)

    2015-07-01

    The penetration of magnetic flux into the high-temperature superconductor YBCO has been observed using a new high-resolution technique based on X-ray magnetic circular dichroism (XMCD). Superconductors coated with thin soft magnetic layers of CoFeB are observed in a scanning x-ray microscope providing cooling of the sample down to 83 K under the influence of external magnetic fields. Resulting electrical currents create an inhomogeneous magnetic field distribution above the superconductor which leads to a local reorientation of the ferromagnetic layer. X-ray absorption measurements with circular polarized radiation allows the analysis of the magnetic flux distribution in the superconductor via the ferromagnetic layer. In this work we present first images taken at 83K with high spatial resolution in the nanoscale.

  17. Magnetic excitations in the heavy-Fermion superconductor URu2Si2

    DEFF Research Database (Denmark)

    Broholm, C.; Lin, H.; Matthews, P.T.

    1991-01-01

    Antiferromagnetic order and fluctuations in the heavy-fermion superconductor URu2Si2 have been studied by magnetic neutron scattering. Below T(N) = 17.5 K, URu2Si2 is a type-I antiferromagnet with an anomalously small ordered moment of (0.04 +/- 0.01)mu-B polarized along the tetragonal c axis...

  18. High performance magnetic bearing systems using high temperature superconductors

    Science.gov (United States)

    Abboud, Robert G.

    1998-01-01

    A magnetic bearing apparatus and a method for providing at least one stabilizing force in a magnetic bearing structure with a superconducting magnetic assembly and a magnetic assembly, by providing a superconducting magnetic member in the superconducting magnetic assembly with a plurality of domains and arranging said superconducting magnetic member such that at least one domain has a domain C-axis vector alignment angularly disposed relative to a reference axis of the magnetic member in the magnetic assembly.

  19. Preparation of Bulky Bi(Pb)-Sr-Ca-Cu-O Superconductor by Magnetized Twin-Roll

    Science.gov (United States)

    Kawahara, Nobuaki; Kawabata, Sanemasa; Enami, Hiroyoshi; Shinohara, Toshiyuki; Hoshizaki, Hiroki; Hasegawa, Masashi; Asai, Shigeo; Imura, Toru

    1990-02-01

    A highly oriented (Bi, Pb)2Sr2Ca2Cu3Ox bulk superconductor has been prepared by magnetized twin-roll processing. In these bulks, plate-like crystal grains were highly oriented by a magnetic and mechanical force. The grain c-axes were parallel to the magnetic field and pressing directions. In fact, both critical current density (Jc) and orientation degree of the sample rolled under 2 T were higher than those of the sample rolled with no magnetic field. The magnetized twin-roll processing is effective not only in enhancing grain-orientation but also in packing to improve Jc.

  20. Sample Size Dependence of Second Magnetization Peak in Type-II Superconductors

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    We show that the second magnetization peak (SMP), i. e., an increase in the magnetization hysteresis loop width in type-II superconductors,vanishes for samples smaller than a critical size. We argue that the SMP is not related to the critical current enhancement but can be well explained within a framework of the thermomagnetic flux-jump instability theory, where flux jumps reduce the absolute irreversible magnetization relative to the isothermal critical state value at low enough magnetic fields. The recovering of the isothermal critical state with increasing field leads to the SMP. The low-field SMP takes place in both low-Tc conventional and high-Tc unconventional superconductors. Our results show that the restoration of the isothermal critical state is responsible for the SMP occurrence in both cases.

  1. Holographic Superconductors with Logarithmic Nonlinear Electrodynamics in an External Magnetic Field

    Science.gov (United States)

    Sheykhi, A.; Shamsi, F.

    2017-03-01

    Based on the matching method, we explore the effects of adding an external magnetic field on the s-wave holographic superconductors when the gauge field is in the form of the logarithmic nonlinear source. First, we obtain the critical temperature as well as the condensation operator in the presence of logarithmic nonlinear electrodynamics and understand that they depend on the nonlinear parameter b. We show that the critical temperature decreases with increasing b, which implies that the nonlinear gauge field makes the condensation harder. Then, we turn on the magnetic field in the bulk and find the critical magnetic field, B c , in terms of the temperature, which also depends on the nonlinear parameter b. We observe that for temperature smaller than the critical temperature, T superconductor with magnetic field in Maxwell theory.

  2. Transmittance properties in a magnetized cold plasma-superconductor periodic multilayer.

    Science.gov (United States)

    Aghajamali, Alireza

    2016-08-10

    This study theoretically investigates the transmittance properties of a one-dimensional photonic crystal containing magnetized cold plasma and high-temperature superconductor materials. The cutoff frequency, as a function of the magnetic field, electron density of the plasma layer, and temperature, will be investigated. The results illustrate that the temperature, electron density, and variations of the magnetic field affect the cutoff frequency. In addition, the shift trend in the cutoff frequency proves to be dependent on the polarization due to the presence of polarization-dependent magnetized cold plasma. Moreover, in temperature-dependent transmittance, weak oscillation and intensity can be seen at higher temperatures, which is in sharp contrast to low-temperature superconductor-dielectric structures. The proposed structure could certainly provide helpful information for the design of new types of antennas, reflectors, and high-pass filters at microwave frequency.

  3. Irreversible magnetization switching at the onset of superconductivity in a superconductor ferromagnet hybrid

    Energy Technology Data Exchange (ETDEWEB)

    Curran, P. J.; Bending, S. J. [Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Kim, J.; Satchell, N.; Witt, J. D. S.; Burnell, G. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Flokstra, M. G.; Lee, S. L. [School of Physics and Astronomy, SUPA, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Cooper, J. F. K.; Kinane, C. J.; Langridge, S. [ISIS, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Isidori, A.; Eschrig, M. [Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX (United Kingdom); Pugach, N. [Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX (United Kingdom); Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University (SYNP MSU), Leninskie Gory, Moscow 119991 (Russian Federation)

    2015-12-28

    We demonstrate that the magnetic state of a superconducting spin valve, that is normally controlled with an external magnetic field, can also be manipulated by varying the temperature which increases the functionality and flexibility of such structures as switching elements. In this case, switching is driven by changes in the magnetostatic energy due to spontaneous Meissner screening currents forming in the superconductor below the critical temperature. Our scanning Hall probe measurements also reveal vortex-mediated pinning of the ferromagnetic domain structure due to the pinning of quantized stray fields in the adjacent superconductor. The ability to use temperature as well as magnetic field to control the local magnetisation structure raises the prospect of potential applications in magnetic memory devices.

  4. Effect of Single Particle Hopping and Out of Plane Magnetic Impurity on Coupled Planar Superconductors

    Science.gov (United States)

    Sardar, Manas; Sa, Debanand

    It is shown that the single particle band motion along the c axis is harmful for superconductivity in anisotropic systems. Variation of Tc with c axis hopping parameter is shown for both the conventional Josephson coupled, planar superconductors and for interlayer pair tunneling mechanism of Wheatley, Hsu, and Anderson (WHA). Effect of out-of-plane magnetic impurity substitution is shown to suppress Tc more for conventional superconductors whereas there is a very sharp decrease of Tc in the WHA mechanism at larger concentrations.

  5. Effect of single particle hopping and out of plane magnetic impurity on coupled planar superconductors

    CERN Document Server

    Sardar, M; Manas Sardar; Debanand Sa

    1994-01-01

    It is shown that the single particle band motion along the c axis is harmful for superconductivity. Variation of T_c with c axis hopping parameter is shown for both the conventional planar superconductors and for interlayer pair tunneling mechanism of Wheatley Hsu and Anderson(WHA).Effect of out of plane magnetic impurity substitution is shown to suppres T_c more for conventional superconductors whereas there is very sharp decrease of T_c in the WHA mechanism at larger concentrations.

  6. Irreversible Magnetization Deep in the Vortex-Liquid State of a 2D Superconductor at High Magnetic Fields

    OpenAIRE

    Maniv, T.; Zhuravlev, V.; Wosnitza, J.; Hagel, J.

    2004-01-01

    The remarkable phenomenon of weak magnetization hysteresis loops, observed recently deep in the vortex-liquid state of a nearly two-dimensional (2D) superconductor at low temperatures, is shown to reflect the existence of an unusual vortex-liquid state, consisting of collectively pinned crystallites of easily sliding vortex chains.

  7. Origin of nonlinear transport across the magnetically induced superconductor-metal-insulator transition in two dimensions.

    Science.gov (United States)

    Seo, Y; Qin, Y; Vicente, C L; Choi, K S; Yoon, Jongsoo

    2006-08-04

    We have studied the effect of perpendicular magnetic fields and temperatures on nonlinear electronic transport in amorphous Ta superconducting thin films. The films exhibit a magnetic field-induced metallic behavior intervening the superconductor-insulator transition in the zero temperature limit. We show that the phase-identifying nonlinear transport in the superconducting and metallic phases arises from an intrinsic origin, not from an electron heating effect. The nonlinear transport is found to accompany an extraordinarily long voltage response time.

  8. Scanning instrumentation for measuring magnetic field trapping in high Tc superconductors

    Science.gov (United States)

    Sisk, R. C.; Helton, A. J.

    1993-01-01

    Computerized scanning instrumentation measures and displays trapped magnetic fields across the surface of high Tc superconductors at 77 K. Data are acquired in the form of a raster scan image utilizing stepping motor stages for positioning and a cryogenic Hall probe for magnetic field readout. Flat areas up to 45 mm in diameter are scanned with 0.5-mm resolution and displayed as false color images.

  9. Quantum Magnetic Excitations from Stripes in Copper-Oxide Superconductors

    OpenAIRE

    Tranquada, J. M.; Woo, H.; Perring, T. G.; Goka, H; Gu, G. D.; Xu, G; Fujita, M.; Yamada, K.

    2004-01-01

    In the copper-oxide parent compounds of the high-transition-temperature superconductors, the valence electrons are localized, one per copper site, due to strong intraatomic Coulomb repulsion. A symptom of the localization is antiferromagnetism, where the spins of localized electrons alternate between up and down. The superconductivity appears when mobile 'holes' are doped into this insulating state, and it coexists with antiferromagnetic fluctuations. In one approach to the coexistence, the h...

  10. Temperature dependence of the upper critical field of type-II superconductors from isothermal magnetization data: Application to high-temperature superconductors

    Science.gov (United States)

    Landau, I. L.; Ott, H. R.

    2002-10-01

    Using the Ginzburg-Landau theory in very general terms, we develop a simple scaling procedure which allows to establish the temperature dependence of the upper critical field Hc2 and the value of the superconducting critical temperature Tc of type-II superconductors from measurements of the reversible isothermal magnetization. An analysis of existing experimental data shows that the normalized dependencies of Hc2 on T/Tc are practically identical for all families of high-Tc superconductors at all temperatures for which the magnetization data are available.

  11. Interaction between ring permanent magnets and bulk Dy-Ba-Cu-O superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kurabayashi, H., E-mail: m208501@sic.shibaura-it.ac.j [Superconducting Materials Laboratory, Shibaura Institute of Technology, 3-7-5, Toyosu, Koto-Ku, Tokyo 135-8548 (Japan); Horikoshi, S.; Suzuki, A.; Ikeda, M.; Wongsatanawarid, A.; Seki, H. [Superconducting Materials Laboratory, Shibaura Institute of Technology, 3-7-5, Toyosu, Koto-Ku, Tokyo 135-8548 (Japan); Akiyama, S. [Magneo-Giken, 1-4-23, Suwa, Iwatsuki-Ku, Saitama-Shi, Saitama-Ken (Japan); Hiragushi, M. [SEIKOW Chemical Engineering, 4-1-31, Suidou-Cho, Amagasaki-Shi, Hyougo-Ken (Japan); Murakami, M. [Superconducting Materials Laboratory, Shibaura Institute of Technology, 3-7-5, Toyosu, Koto-Ku, Tokyo 135-8548 (Japan)

    2010-11-01

    A combination of bulk Dy-Ba-Cu-O superconductors and permanent magnets can be used for various rotational applications such as flywheel energy storage and magnetic bearings. For practical applications, there are two important parameters: the levitation force and the stiffness. Since the superconductor and magnets are installed in a closed space, the attractive force is another important parameter that we should take care. In this study, we measured the levitation force and the stiffness by changing the thickness of a ring permanent magnet. We used ring Fe-Nd-B magnets 120 mm in outer diameter and 70 mm in inner diameter with the thicknesses of 5-40 mm. For superconductors, we used single-domain bulk Dy-Ba-Cu-O 47 mm in diameter and 10 mm in thickness. Six pellets of Dy-Ba-Cu-O were placed concentrically such that the inner diameter becomes 70 mm. The levitation forces increased with increasing the thickness of the permanent magnet but tended to saturate.

  12. Levitation force of small clearance superconductor-magnet system under non-coaxial condition

    Science.gov (United States)

    Xu, Jimin; Jin, Yingze; Yuan, Xiaoyang; Miao, Xusheng

    2017-03-01

    A novel superconducting tilting-pad bearing was proposed for the advanced research of reusable liquid hydrogen turbopump in liquid rocket. The bearing is a combination of superconducting magnetic bearing and hydrodynamic fluid-film bearing. Since the viscosity of cryogenic fuel to activate superconducting state and form hydrodynamic fluid-film is very low, bearing clearance will be very small. This study focuses on the investigation of superconducting levitation force in this kind of small clearance superconductor-magnet system. Based on Bean critical state model and three-dimensional finite element method, an analysis method is presented to obtain the levitation force under such situation. Since the complicated operational conditions and structural arrangement for application in liquid rocket, center lines of bulk superconductor and magnet rotor will usually be in non-coaxial state. Superconducting levitation forces in axial direction and radial direction under non-coaxial situation are also analyzed by the presented method.

  13. Magnetic Lifshitz transition and its consequences in multi-band iron-based superconductors

    Science.gov (United States)

    Ptok, Andrzej; Kapcia, Konrad J.; Cichy, Agnieszka; Oleś, Andrzej M.; Piekarz, Przemysław

    2017-01-01

    In this paper we address Lifshitz transition induced by applied external magnetic field in a case of iron-based superconductors, in which a difference between the Fermi level and the edges of the bands is relatively small. We introduce and investigate a two-band model with intra-band pairing in the relevant parameters regime to address a generic behaviour of a system with hole-like and electron-like bands in external magnetic field. Our results show that two Lifshitz transitions can develop in analysed systems and the first one occurs in the superconducting phase and takes place at approximately constant magnetic field. The chosen sets of the model parameters can describe characteristic band structure of iron-based superconductors and thus the obtained results can explain the experimental observations in FeSe and Co-doped BaFe2As2 compounds. PMID:28165043

  14. Two kinds of magnetic gauge potentials due to coherent effect in two-gap superconductor

    Science.gov (United States)

    Shi, Xuguang

    2016-10-01

    Two-component Ginzburg-Landau model with one magnetic gauge potential can be used to describe the physical properties of two-gap superconductor. When the order parameters in two-gap superconductor have different phases, the gauge invariance will be destroyed. In order to preserve gauge invariance, two kinds of gauge potentials must be introduced. For seeking the origins of two kinds of gauge potentials, one suggests two kinds of order parameters are in the coherent state. Therefore, two different gauge potentials and masses of the order parameters arise through deducing the super-current of the coherent state. As a result, two different gauge potentials lead to different magnetic fields at the zero points of the order parameters. In other places, the gauge potentials have no contributions to the magnetic field. Moreover, the topological properties of two different gauge potentials are discussed in detail.

  15. Anisotropy Effect on Levitation Performance of Bulk High-Tc Superconductors Above a Permanent Magnet Guideway

    Science.gov (United States)

    Zheng, Jun; Liao, Xinglin; Jing, Hailian; Lin, Qunxu; Ma, Guangtong; Yen, Fei; Wang, Suyu; Wang, Jiasu

    The anisotropy properties of bulk high-temperature superconductors (HTSCs) are taken into consideration for the application of high-temperature superconducting (HTS) Maglev systems, which are especially based on the different flux-trapping capabilities as well as critical current density, Jc, values between the growth section boundary (GSB) and the growth sections (GS) in bulk superconductors. By adjusting the angle between the GSB of bulk HTSCs and the strongest magnetic field position of a permanent magnet guideway (PMG), the levitation force and its relaxation processes are compared at different field-cooling conditions. Experimental results show that the levitation capability and the suppression of levitation force decay can be enhanced by optimizing the GS/GSB alignment of every bulk HTSC above the PMG. Meanwhile, our conclusions may provide references to other HTS maglev systems with small levitation gaps, i.e., superconducting magnetic bearings.

  16. Magnetic Excitations in the Ferromagentic Superconductor UGe2

    Science.gov (United States)

    Huxley, A. D.; Raymond, S.; Ressouche, E.

    2003-11-01

    We report that the uniform magnetization is not conserved in the magnetic excitation spectrum of UGe2. The measured spectrum is therefore different from that in d-electron ferromagnetic metals in a way that would facilitate magnetically mediated superconductivity.

  17. Magneto-thermal phenomena in bulk high temperature superconductors subjected to applied AC magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Vanderbemden, P; Laurent, P [SUPRATECS and Department of Electrical Engineering and Computer Science B28, Sart-Tilman, B-4000 Liege (Belgium); Fagnard, J-F [SUPRATECS, Royal Military Academy of Belgium, Avenue de la Renaissance, B-1000 Brussels (Belgium); Ausloos, M [SUPRATECS and Department of Physics B5, Sart-Tilman, B-4000 Liege (Belgium); Hari Babu, N [Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University, West London UB8 3PH (United Kingdom); Cardwell, D A, E-mail: Philippe.Vanderbemden@ulg.ac.b [Bulk Superconductivity Group, Engineering Department, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)

    2010-07-15

    In the present work we study, both theoretically and experimentally, the temperature increase in a bulk high temperature superconductor subjected to applied AC magnetic fields of large amplitude. We calculate analytically the equilibrium temperatures of the bulk sample as a function of the experimental parameters using a simple critical state model for an infinitely long type-II superconducting slab or cylinder. The results show the existence of a limit heat transfer coefficient (AU{sub lim}) separating two thermal regimes with different characteristics. The theoretical analysis predicts a 'forbidden' temperature window within which the temperature of the superconductor can never stabilize when the heat transfer coefficient is small. In addition, we determine analytical expressions for two threshold fields H{sub tr1} and H{sub tr2} characterizing the importance of magneto-thermal effects and show that a thermal runaway always occurs when the field amplitude is larger than H{sub tr2}. The theoretical predictions of the temperature evolution of the bulk sample during a self-heating process agree well with the experimental data. The simple analytical study presented in this paper enables order of magnitude thermal effects to be estimated for simple superconductor geometries under applied AC magnetic fields and can be used to predict the influence of experimental parameters on the self-heating characteristics of bulk type-II superconductors.

  18. The upper critical magnetic field of holographic superconductor with conformally invariant power-Maxwell electrodynamics

    CERN Document Server

    Sheykhi, A; Davatolhagh, S

    2016-01-01

    The properties of $(d-1)$-dimensional $s$-wave holographic superconductor in the presence of power-Maxwell field is explored. We study the probe limit in which the scalar and gauge fields do not backreact on the background geometry. Our study is based on the matching of solutions on the boundary and on the horizon at some intermediate point. At first, the case without external magnetic field is considered, and the critical temperature is obtained in terms of the charge density, the dimensionality, and the power-Maxwell exponent. Then, a magnetic field is turned on in the $d$-dimensional bulk which can influence the $(d-1)$-dimensional holographic superconductor at the boundary. The phase behavior of the corresponding holographic superconductor is obtained by computing the upper critical magnetic field in the presence of power-Maxwell electrodynamics, characterized by the power exponent $q$. Interestingly, it is observed that in the presence of magnetic field, the physically acceptable phase behavior of the ho...

  19. Interplay between magnetism and superconductivity in iron-chalcogenide superconductors: crystal growth and characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Wen Jinsheng; Birgeneau, R J [Physics Department, University of California, Berkeley, CA 94720 (United States); Xu Guangyong; Gu Genda; Tranquada, J M, E-mail: jinshengwen@berkeley.edu, E-mail: jtran@bnl.gov [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2011-12-15

    In this review, we present a summary of results on single crystal growth of two types of iron-chalcogenide superconductors, Fe{sub 1+y}Te{sub 1-x}Se{sub x} (11), and A{sub x}Fe{sub 2-y}Se{sub 2} (A = K, Rb, Cs, Tl, Tl/K, Tl/Rb), using Bridgman, zone-melting, vapor self-transport and flux techniques. The superconducting and magnetic properties (the latter gained mainly from neutron scattering measurements) of these materials are reviewed to demonstrate the connection between magnetism and superconductivity. It will be shown that for the 11 system, while static magnetic order around the reciprocal lattice position (0.5, 0) competes with superconductivity, spin excitations centered around (0.5, 0.5) are closely coupled to the materials' superconductivity; this is made evident by the strong correlation between the spectral weight around (0.5, 0.5) and the superconducting volume fraction. The observation of a spin resonance below the superconducting temperature, T{sub c}, and the magnetic-field dependence of the resonance emphasize the close interplay between spin excitations and superconductivity, similar to cuprate superconductors. In A{sub x}Fe{sub 2-y}Se{sub 2}, superconductivity with T{sub c} {approx} 30 K borders an antiferromagnetic insulating phase; this is closer to the behavior observed in the cuprates but differs from that in other iron-based superconductors.

  20. Interplay between magnetism and superconductivity in iron-chalcogenide superconductors: crystal growth and characterizations

    Science.gov (United States)

    Wen, Jinsheng; Xu, Guangyong; Gu, Genda; Tranquada, J. M.; Birgeneau, R. J.

    2011-12-01

    In this review, we present a summary of results on single crystal growth of two types of iron-chalcogenide superconductors, Fe1+yTe1-xSex (11), and AxFe2-ySe2 (A = K, Rb, Cs, Tl, Tl/K, Tl/Rb), using Bridgman, zone-melting, vapor self-transport and flux techniques. The superconducting and magnetic properties (the latter gained mainly from neutron scattering measurements) of these materials are reviewed to demonstrate the connection between magnetism and superconductivity. It will be shown that for the 11 system, while static magnetic order around the reciprocal lattice position (0.5, 0) competes with superconductivity, spin excitations centered around (0.5, 0.5) are closely coupled to the materials' superconductivity; this is made evident by the strong correlation between the spectral weight around (0.5, 0.5) and the superconducting volume fraction. The observation of a spin resonance below the superconducting temperature, Tc, and the magnetic-field dependence of the resonance emphasize the close interplay between spin excitations and superconductivity, similar to cuprate superconductors. In AxFe2-ySe2, superconductivity with Tc ~ 30 K borders an antiferromagnetic insulating phase; this is closer to the behavior observed in the cuprates but differs from that in other iron-based superconductors.

  1. Magnetic x-ray microscopy at low temperatures – Visualization of flux distributions in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Stahl, Claudia, E-mail: stahl@is.mpg.de; Ruoß, Stephen; Weigand, Markus; Bechtel, Michael; Schütz, Gisela [Max Planck Institute for Intelligent Systems, Heisenbergstraße 3, 70569 Stuttgart (Germany); Albrecht, Joachim [Research Institute for Innovative Surfaces, FINO, Aalen University, Beethovenstraße 1, 73430 Aalen (Germany)

    2016-01-28

    X-ray Magnetic Circular Dichroism (XMCD) microscopy at liquid nitrogen temperature has been performed on bilayers of high-T{sub c} superconducting YBCO (YBa{sub 2}Cu{sub 3}O{sub 7-δ}) and soft-magnetic Co{sub 40}Fe{sub 40}B{sub 20}. This should allow us to map the magnetic flux density distribution in the current-carrying state of the superconductor with high spatial resolution. For that purpose the UHV scanning X-ray microscope MAXYMUS has been upgraded by a MMR Micro Miniature Joule-Thompson cryostat capable of temperatures between 75 K and 580 K. Resulting XMCD images of the magnetic flux density in the superconductor with a field of view ranging from millimeters to micrometers are presented. The microscope’s unique combination of total electron yield (TEY) measurements together with low temperatures offers novel possibilities concerning the current transport in superconductors on small length scales.

  2. Effects of Size, deGennes and Ginzburg-Landau Parameters on the Magnetic Susceptibility of an Isotropic Superconductor

    Science.gov (United States)

    Aguirre, C. A.; González, J. D.; Barba-Ortega, J.

    2016-01-01

    The magnetic signature of a nanoscopic superconductor immersed in a magnetic applied field H_e is calculated numerically. The calculated magnetic susceptibility partial M / partial H_e of a superconducting nanoprism shows discontinuities and a quasiperiodic modulation at the vortex transition fields H_T (fields for which one or several vortices enter/leave the sample). In this contribution, we studied the influence of the sample size, the Ginzburg-Landau parameter κ and the deGennes parameter b on the magnetic susceptibility in a type-II isotropic superconductor. We found distinct signatures of the magnetic susceptibility when superconducting samples of two and three dimensions are considered.

  3. Development of Y-Ba-Cu-O Superconductors for Magnetic Bearings

    Science.gov (United States)

    Selvamanickam, V.; Pfaffenbach, K.; Sokolowski, R. S.; Zhang, Y.; Salama, K.

    1996-01-01

    The material requirements, material manufacturing and magnetic properties that are relevant to fabrication of High Temperature Superconductor (HTS) magnetic bearings have been discussed. It is found that the seeded-melt-texturing method can be used to fabricate the single domain material that is required to achieve the best magnetic properties. Trapped-field mapping has been used as a non-destructive tool to determine the single-domain nature of the HTS material and quantity of the HTS disks. Both the trapped field and the levitation force of the Y-Ba-Cu-O disks are found to be strongly sensitive to the oxygen content.

  4. Bipolaron theory of the low magnetic field properties of high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrov, A.S.; Traven, S.V. (Moscow Engineering Physics Inst. (USSR))

    1991-02-01

    The low magnetic field properties of the layered high-temperature superconductors are studied in the frame of the two-dimensional heavy charged Bose-gas model. The temperature dependencies of the magnetic field penetration depth {lambda}{sub H}(T) and of the lower critical field H{sub c1}(T) are calculated in the London limit. The discrepancy between the temperature dependence of the penetration depth from the {mu}SR measurements and that from the ac susceptibility and magnetization measurements is discussed. (orig.).

  5. Counter magnetization of SmCo5 permanent magnet by YBCO/Ag composite bulk superconductor — A competing interaction picture

    Science.gov (United States)

    Parthasarathy, R.; Lakshmi, M. M.; Seshubai, V.

    2012-06-01

    We report here for the first time the counter magnetization of an SmCo5 permanent magnet in the presence of a YBCO/Ag composite bulk superconductor. This remarkable phenomenon has been observed during our experiments to measure the levitation force of the superconductor. The inclination to study the effects of the superconductor on the permanent magnet led us to observe this surprising and curious phenomenon for the first time. A complete M-H hysteresis loop of the SmCo5 permanent magnet has been recorded using the bulk superconductor itself as a magnet. We present some of the initial results which are interesting and we discuss the possible kind of interaction that could lead to our observations.

  6. A close-up of the lower part of a 13 kA current lead. The high-temperature superconductor (on the left in the photo) with the low-temperature superconductor (on the right). Resting in liquid helium, the low-temperature superconductor is connected to the bus-bars conveying the current to the LHC magnets.

    CERN Multimedia

    2004-01-01

    A close-up of the lower part of a 13 kA current lead. The high-temperature superconductor (on the left in the photo) with the low-temperature superconductor (on the right). Resting in liquid helium, the low-temperature superconductor is connected to the bus-bars conveying the current to the LHC magnets.

  7. Disorder-promoted C4-symmetric magnetic order in iron-based superconductors

    Science.gov (United States)

    Hoyer, Mareike; Fernandes, Rafael M.; Levchenko, Alex; Schmalian, Jörg

    2016-04-01

    In most iron-based superconductors, the transition to the magnetically ordered state is closely linked to a lowering of structural symmetry from tetragonal (C4) to orthorhombic (C2). However, recently, a regime of C4-symmetric magnetic order has been reported in certain hole-doped iron-based superconductors. This novel magnetic ground state can be understood as a double-Q spin density wave characterized by two order parameters M1 and M2 related to each of the two Q vectors. Depending on the relative orientations of the order parameters, either a noncollinear spin-vortex crystal or a nonuniform charge-spin density wave could form. Experimentally, Mössbauer spectroscopy, neutron scattering, and muon spin rotation established the latter as the magnetic configuration of some of these optimally hole-doped iron-based superconductors. Theoretically, low-energy itinerant models do support a transition from single-Q to double-Q magnetic order, but with nearly degenerate spin-vortex crystal and charge-spin density wave states. In fact, extensions of these low-energy models including additional electronic interactions tip the balance in favor of the spin-vortex crystal, in apparent contradiction with the recent experimental findings. In this paper we revisit the phase diagram of magnetic ground states of low-energy multiband models in the presence of weak disorder. We show that impurity scattering not only promotes the transition from C2 to C4-magnetic order, but it also favors the charge-spin density wave over the spin-vortex crystal phase. Additionally, in the single-Q phase, our analysis of the nematic coupling constant in the presence of disorder supports the experimental finding that the splitting between the structural and stripe-magnetic transition is enhanced by disorder.

  8. Superconducting Coherence Length and Magnetic Penetration Depth of a p-wave Holographic Superconductor

    CERN Document Server

    Zeng, Hua-Bi; Zong, Hong-Shi

    2009-01-01

    A classical SU(2) Einstein-Yang-Mills theory in 3+1 dimensional anti-de Sitter spacetime is believed to be dual to a p-wave superconductor in 2+1 dimensional flat spacetime. In order to calculate the superconductiong coherence length $\\xi$ of the holographic superconductor near the superconducting phase transition point, we study the perturbation of the gravity theory analytically. The superconductiong coherence length $\\xi$ is found to be proportional to $(1-T/T_c)^{-1/2}$ near the critical temperature $T_c$. We also obtain the magnetic penetration depth $\\lambda\\propto(T_c-T)^{1/2}$ by adding a small external homogeneous magnetic field. The results agree with the Ginzburg-Landau theory.

  9. Extracting, Tracking, and Visualizing Magnetic Flux Vortices in 3D Complex-Valued Superconductor Simulation Data.

    Science.gov (United States)

    Guo, Hanqi; Phillips, Carolyn L; Peterka, Tom; Karpeyev, Dmitry; Glatz, Andreas

    2016-01-01

    We propose a method for the vortex extraction and tracking of superconducting magnetic flux vortices for both structured and unstructured mesh data. In the Ginzburg-Landau theory, magnetic flux vortices are well-defined features in a complex-valued order parameter field, and their dynamics determine electromagnetic properties in type-II superconductors. Our method represents each vortex line (a 1D curve embedded in 3D space) as a connected graph extracted from the discretized field in both space and time. For a time-varying discrete dataset, our vortex extraction and tracking method is as accurate as the data discretization. We then apply 3D visualization and 2D event diagrams to the extraction and tracking results to help scientists understand vortex dynamics and macroscale superconductor behavior in greater detail than previously possible.

  10. High-temperature superconductors in high-field magnets

    NARCIS (Netherlands)

    Weijers, Hubertus Wilhelmus

    2009-01-01

    The properties of both BSCCO conductors and YBCO coated conductors and coils are studied to assess their applicability in high-field magnets. First, the magnetic field dependence of the critical current density in these HTS conductors is measured at 4.2 K in magnetic field conditions ranging from s

  11. Charge orders, magnetism and pairings in the cuprate superconductors.

    Science.gov (United States)

    Kloss, T; Montiel, X; de Carvalho, V S; Freire, H; Pépin, C

    2016-08-01

    We review the recent developments in the field of cuprate superconductors with special focus on the recently observed charge order in the underdoped compounds. We introduce new theoretical developments following the study of the antiferromagnetic quantum critical point in two dimensions, in which preemptive orders in both charge and superconducting (SC) sectors emerge, that are in turn related by an SU(2) symmetry. We consider the implications of this proliferation of orders in the underdoped region, and provide a study of the type of fluctuations which characterize the SU(2) symmetry. We identify an intermediate energy scale where the SC fluctuations are dominant and argue that they are unstable towards the formation of a resonant excitonic state at the pseudogap temperature T (*). We discuss the implications of this scenario for a few key experiments.

  12. Develop and test an internally cooled, cabled superconductor (ICCS) for large scale MHD magnets

    Energy Technology Data Exchange (ETDEWEB)

    Marston, P.G.; Hale, J.R.; Dawson, A.M.

    1990-04-30

    The work conducted under DOE/PETC Contract DE-AC22-84PC70512 has included four principal tasks, (1) development of a Design Requirements Definition for a retrofit MHD magnet system, (2) analysis of an internally cooled, cabled superconductor (ICCS) to use in that design, (3) design of an experiment to test a subscale version of that conductor, which is a NbTi, copper stabilized superconductor, and (4) proof-of-concept testing of the conductor. The program was carried forth through the third task with very successful development and test of a conventional ICCS conductor with 27 multifilamentary copper-superconductor composite strands and a new concept conductor in which, in each triplet, two strands were pure copper and the third strand was a multifilamentary composite. In reviewing the magnet design and the premises for the conductor design it became obvious that, since the principal source of perturbation in MHD magnets derives from slippage between coils, or between turns in a coil, thereby producing frictional heat which must flow through the conductor sheath and the helium to the superconductor strands, an extra barrier might be highly effective in enhancing magnet stability and protection. This concept was developed and a sample conductor manufactured and tested in comparison with an identical conductor lacking such an additional barrier. Results of these conductor tests confirm the potential value of such a barrier. As the work of tasks 1 through 3 has been reported in detail in quarterly and semiannual reports, as well as in special reports prepared throughout the course of this project, this report reviews early work briefly and then discusses this last phase in great detail. 8 refs., 36 figs.

  13. Effect of external magnetic field on the coexistence of SC and AFM in iron based superconductors

    Science.gov (United States)

    Goi, S. K.; Pradhan, B.; Behera, Srikanta; Parida, P. K.; Mishra, R. N.

    2017-03-01

    We have studied the interplay of antiferromagnetism and superconductivity in presence of an applied external magnetic field for the iron based superconductors. For the purpose we have proposed a model Hamiltonian and solved it self-consistently by using the Zubarev's technique of double time Green's function technique. The self-consistent gap equations are solved numerically and interpreted the gap values from the of density of states plots.

  14. The topological structure of the integral quantum Hall effect in magnetic semiconductor-superconductor hybrids

    Institute of Scientific and Technical Information of China (English)

    Ren Ji-Rong; Zhu Hui

    2009-01-01

    An unconventional integer quantum Hall regime was found in magnetic semiconductor-superconductor hybrids.By making use of the decomposition of the gauge potential on a U(1) principal fibre bundle over k-space, we study the topological structure of the integral Hall conductance. It is labeled by the Hopf index β and the Brouwer degree η. The Hall conductance topological current and its evolution is discussed.

  15. Magnetic studies in organic superconductors bis(tetramethyltetraselenafulvalene) perchlorate: Upper critical fields and vortex matters

    Science.gov (United States)

    Oh, Jeong Il

    A thermodynamic determination of the upper critical field Hc2 in the quasi-one dimensional molecular organic superconductor (TMTSF) 2ClO4 has been obtained for magnetic field accurately aligned along the in-plane, inter-chain direction by utilizing silicon cantilever magnetometer technology. This magnetically-measured upper critical field, simultaneously confirmed by electrical transport measurements, was found to well-exceed all paramagnetic limits known to date for spin singlet superconductors, strongly indicating that (TMTSF)2ClO4 is a spin triplet superconductor. Also, we were able to investigate novel structure in the upper critical field, where we observed that Hc2(T) has three different temperature regimes, characterized by an usual upturn at a temperature T* ˜ 0.2 K and a very unusual kink at a temperature T0 ˜ 1.04 K. In addition, the magnetic field-temperature superconducting vortex phase diagram of (TMTSF)2ClO4 has been obtained. The phase diagram showed a variety of vortex phases, including solid (Bragg lattice and disordered glass) and liquid (liquid-1 and liquid-2) subphases. A distinct irreversibility line was found, likely separating the solid from the liquid phase. Within the solid phase, we observed an unusual inverse transition driven by the pinning force, splitting the solid phase into a disordered glass and a Bragg lattice. Also, within the Bragg lattice, we observed a temperature-independent magnetic crossover line at low field (˜0.05 T), interpreted as possibly indicating the existence of multiple Tc's in (TMTSF)2X, further evidence for claiming this system to be a triplet superconductor.

  16. The size effect on the magnetic levitation force of MgB2 bulk superconductors

    Science.gov (United States)

    Savaskan, B.; Koparan, E. T.; Güner, S. B.; Celik, S.; Yanmaz, E.

    2016-12-01

    In this study, the size effect on the magnetic levitation performance of disk-shaped MgB2 bulk superconductors and permanent magnets was investigated. MgB2 samples with varying diameters of 13 mm, 15 mm and 18 mm, each of which were 2 g in mass, were prepared by two-step solid state reaction method. Vertical levitation force measurements under both zero-field-cooled (ZFC) and field-cooled (FC) regimes were carried out at different temperatures of 20, 24 and 28 K. It was determined that the levitation force of the MgB2 strongly depends on both the diameters of the sample and the permanent magnet. In ZFC regime, the maximum levitation force value for the permanent magnet and the sample 18 mm in diameters reached to the 8.41 N at 20 K. In addition, in FC regime, attractive and repulsive force increased with increasing diameters of the sample and the permanent magnet. In that, the sample with 18 mm in diameter showed the highest attractive force value -3.46 N at 20 K and FC regime. The results obtained in this study are very useful in magnetic levitation devices as there is no detailed study on the size of superconductors and permanent magnets.

  17. Magnetic levitation and its application for education devices based on YBCO bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yang, W.M., E-mail: yangwm@snnu.edu.cn; Chao, X.X.; Guo, F.X.; Li, J.W.; Chen, S.L.

    2013-10-15

    Highlights: • A small superconducting maglev propeller system has been designed and constructed based on YBCO bulk superconductors. • Several small maglev vehicle models have been designed and constructed based on YBCO bulk superconductors. • The models can be used as experimental or demonstration devices for the magnetic levitation applications. -- Abstract: A small superconducting maglev propeller system, a small spacecraft model suspending and moving around a terrestrial globe, several small maglev vehicle models and a magnetic circuit converter have been designed and constructed. The track was paved by NdFeB magnets, the arrangement of the magnets made us easy to get a uniform distribution of magnetic field along the length direction of the track and a high magnetic field gradient in the lateral direction. When the YBCO bulks mounted inside the vehicle models or spacecraft model was field cooled to LN{sub 2} temperature at a certain distance away from the track, they could be automatically floating over and moving along the track without any obvious friction. The models can be used as experimental or demonstration devices for the magnetic levitation applications.

  18. Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y-Ba-Cu-O superconductor

    OpenAIRE

    Philippe, Matthieu; Ainslie, Mark D.; Wera, Laurent; Fagnard, Jean-François; Dennis, Anthony; Shi, Yunhua; Cardwell, David A.; Vanderheyden, Benoît; Vanderbemden, Philippe

    2015-01-01

    Bulk, high temperature superconductors have significant potential for use as powerful permanent magnets in a variety of practical applications due to their ability to trap record magnetic fields. In this paper, soft ferromagnetic sections are combined with a bulk, large grain Y-Ba-Cu-O (YBCO) high temperature superconductor to form superconductor/ferromagnet (SC/FM) hybrid structures. We study how the ferromagnetic sections influence the shape of the profile of the trapped magnetic induction ...

  19. A moving target: responding to magnetic and structural disorder in lanthanide- and actinide-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Eric D [Los Alamos National Laboratory; Mitchell, Jeremy N [Los Alamos National Laboratory; Booth, C H [LBNL

    2009-01-01

    The effects of various chemical substitutions and induced lattice disorder in the Ce- and Pu-based 115 superconductors are reviewed, with particular emphasis on results from x-ray absorption fine structure (XAFS) measurements. The competition between spin, charge, and lattice interactions is at the heart of many of the strongly-correlated ground states in materials of current interest, such as in colossal magnetoresistors and high-temperature superconductors. This relationship is particularly strong in the CeTIn{sub 5} and PuTGa{sub 5} series (T = Co, Rh, Ir) of heavy-fermion superconductors. In these systems (figure 1), competition between bulk magnetic and non-magnetic ground states, as well as between superconducting and normal states, are directly related to local properties around the lanthanide or actinide ion, such as the nearest-neighbor bond lengths and the local density of states at the Fermi level. Tiny changes in the latter values can easily tip the balance from one ground state to another. This paper reviews recent work by the authors exploring the relationship between local crystal and electronic structure and ground state magnetic and conducting properties in the Ce- and Pu-based 115 materials.

  20. Develop and test an Internally Cooled, Cabled Superconductor (ICCS) for large scale MHD magnets

    Science.gov (United States)

    Marston, P. G.; Hale, J. R.; Dawson, A. M.

    1990-04-01

    The work included four principal tasks: (1) development of a design requirements definition for a retrofit MHD magnet system; (2) analysis of an internally cooled, cabled superconductor (ICCS) to use in that design; (3) design of an experiment to test a subscale version of that conductor, which is a NbTi, copper stabilized superconductor; and (4) proof-of-concept testing of the conductor. The program was carried forth through the third task with very successful development and test of a conventional ICCS conductor with 27 multifilamentary copper-superconductor composite strands and a new concept conductor in which, in each triplet, two strands were pure copper and the third strand was a multifilamentary composite. In reviewing the magnet design and the premises for the conductor design it became obvious that an extra barrier might be highly effective in enhancing magnet stability and protection. This concept was developed and a sample conductor manufactured and tested in comparison with an identical conductor lacking such an additional barrier. Results of these conductor tests confirm the potential value of such a barrier. Since the work of tasks 1 through 3 has been reported in detail in quarterly and semiannual reports, as well as in special reports prepared throughout the course of this project, this report reviews early work briefly and then discusses this last phase in great detail.

  1. Design of Nb3Sn magnetic devices to study the superconductor degradation under variable mechanical load

    CERN Document Server

    Regis, Federico

    2009-01-01

    The Large Hadron Collider (LHC) is a two-ring, superconducting synchrotron accelerator and collider installed in a 27 km long tunnel aiming at the discovery of the Higgs particle and the study of rare events with center mass collision energies of up to 14 TeV. The number of collisions per unit of area and time in a collider are evaluated trough the Luminosity function. Inside the LHC, superconducting magnets aligned with a precision of a few tenths of millimeters are used to bend and focus the particle trajectories. The LHC can be considered as the state of the art for superconducting magnets using the Nb-Ti superconductor technology. Therefore, a higher luminosity and beam energy can be achieved in the LHC only by using a more performing superconductor, such as the Nb3Sn. This is considered as the most suitable superconductor to be used in high field magnets, allowing peak field of the order of 15 T. Nevertheless, the critical current jc variations in a Nb3Sn has been found as strongly dependent on the mecha...

  2. Magnetic proximity effect and superconducting triplet correlations at the cuprate superconductor and oxide spin valve interface

    Science.gov (United States)

    Ovsyannikov, G. A.; Constantinian, K. Y.; Demidov, V. V.; Khaydukov, Yu. N.

    2016-10-01

    A heterostructure consisting of a cuprate superconductor YBa2Cu3O7-δ and a ruthenate/manganite (SrRuO3/La0.7Sr0.3MnO3) spin valve was studied using SQUID magnetometry, ferromagnetic resonance, and neutron reflectometry. It is shown that because of the magnetic proximity effect a magnetic moment is excited in the superconducting portion of the heterostructure, whereas the magnetic moment in the spin valve becomes suppressed. The experimentally obtained value of a typical penetration depth of a magnetic moment into the superconductor is significantly greater than the coherence length of the cuprate superconductor, which indicates that the induced magnetic moment mechanism of Cu atoms is dominant. The mesastructure prepared by adding niobium film as a second superconducting electrode to the existing heterostructure, exhibited a superconducting current (dc Josephson effect) at interlayer thicknesses that are much greater than the coherence length of the ferromagnetic materials. The maximum of the critical current density dependence on the thickness of the spin valve material corresponds to the interlayer coherence length, which agrees with the theoretical predictions associated with spin-triplet pairing. The superconducting current is observed at magnetic fields that are two orders of magnitude greater than the field corresponding to the occurrence of one magnetic flux quantum in the mesastructure. The ratio of the second harmonic of the current-phase dependence of the mesastructure superconducting current to the first, determined according to the dependence of the Shapiro steps on the amplitude of microwave exposure, did not exceed 50%.

  3. Magnetic characterisation of large grain, bulk Y-Ba-Cu-O superconductor-soft ferromagnetic alloy hybrid structures

    Science.gov (United States)

    Philippe, M. P.; Fagnard, J.-F.; Kirsch, S.; Xu, Z.; Dennis, A. R.; Shi, Y.-H.; Cardwell, D. A.; Vanderheyden, B.; Vanderbemden, P.

    2014-07-01

    Large grain, bulk Y-Ba-Cu-O (YBCO) high temperature superconductors (HTS) have significant potential for use in a variety of practical applications that incorporate powerful quasi-permanent magnets. In the present work, we investigate how the trapped field of such magnets can be improved by combining bulk YBCO with a soft FeNi, ferromagnetic alloy. This involves machining the alloy into components of various shapes, such as cylinders and rings, which are attached subsequently to the top surface of a solid, bulk HTS cylinder. The effect of these modifications on the magnetic hysteresis curve and trapped field of the bulk superconductor at 77 K are then studied using pick-up coil and Hall probe measurements. The experimental data are compared to finite element modelling of the magnetic flux distribution using Campbell’s algorithm. Initially we establish the validity of the technique involving pick-up coils wrapped around the bulk superconductor to obtain its magnetic hysteresis curve in a non-destructive way and highlight the difference between the measured signal and the true magnetization of the sample. We then consider the properties of hybrid ferromagnet/superconductor (F/S) structures. Hall probe measurements, together with the results of the model, establish that flux lines curve outwards through the ferromagnet, which acts, effectively, like a magnetic short circuit. Magnetic hysteresis curves show that the effects of the superconductor and the ferromagnet simply add when the ferromagnet is saturated fully by the applied field. The trapped field of the hybrid structure is always larger than that of the superconductor alone below this saturation level, and especially when the applied field is removed. The results of the study show further that the beneficial effects on the trapped field are enhanced when the ferromagnet covers the entire surface of the superconductor for different ferromagnetic components of various shapes and fixed volume.

  4. Scaling of the equilibrium magnetization in the mixed state of type-II superconductors

    Science.gov (United States)

    Landau, I. L.; Ott, H. R.

    2005-04-01

    We discuss the analysis of mixed-state magnetization data of type-II superconductors using a recently developed scaling procedure. It is based on the fact that, if the Ginzburg-Landau parameter κ does not depend on temperature, the magnetic susceptibility χ(H,T) is a universal function of H/Hc2(T), leading to a simple relation between magnetizations at different temperatures. Although this scaling procedure does not provide absolute values of the upper critical field Hc2(T), its temperature variation can be established rather accurately. This provides an opportunity to validate theoretical models that are usually employed for the evaluation of Hc2(T) from equilibrium magnetization data. In the second part of the paper we apply this scaling procedure for a discussion of the notorious first order phase transition in the mixed state of high-Tc superconductors. Our analysis, based on experimental magnetization data available in the literature, shows that the shift of the magnetization accross the transition may adopt either sign, depending on the particular chosen sample. We argue that this observation is inconsistent with the interpretation that this transition always represents the melting transition of the vortex lattice.

  5. A portable magnetic field of >3 T generated by the flux jump assisted, pulsed field magnetization of bulk superconductors

    Science.gov (United States)

    Zhou, Difan; Ainslie, Mark D.; Shi, Yunhua; Dennis, Anthony R.; Huang, Kaiyuan; Hull, John R.; Cardwell, David A.; Durrell, John H.

    2017-02-01

    A trapped magnetic field of greater than 3 T has been achieved in a single grain GdBa2Cu3O7-δ (GdBaCuO) bulk superconductor of diameter 30 mm by employing pulsed field magnetization. The magnet system is portable and operates at temperatures between 50 K and 60 K. Flux jump behaviour was observed consistently during magnetization when the applied pulsed field, Ba, exceeded a critical value (e.g., 3.78 T at 60 K). A sharp dBa/dt is essential to this phenomenon. This flux jump behaviour enables the magnetic flux to penetrate fully to the centre of the bulk superconductor, resulting in full magnetization of the sample without requiring an applied field as large as that predicted by the Bean model. We show that this flux jump behaviour can occur over a wide range of fields and temperatures, and that it can be exploited in a practical quasi-permanent magnet system.

  6. Nonlinear Temperature Dependence of Magnetization of Two-Band Superconductors Near Upper Critical Field

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Temperature dependence of the magnetization M(T) of two-band superconductors is studied in the vicinity of upper critical field Hc2 by using a two-band Ginzburg-Landau (GL) theory. It is shown that magnetization M(T) has a nonlinear character due to positive curvature of upper critical field Hc2(T) and temperature dependence of effective Ginzburg-Landau parameter (n)eff(T). The results are shown to be in qualitative agreement with experimental data for the superconducting magnesium diboride, MgB2.

  7. Effect of size on levitation force in a magnet/superconductor system

    Science.gov (United States)

    Yang, Z. J.; Hull, J. R.

    1996-03-01

    We consider a model system consisting of an infinitely long magnetic dipole line placed symmetrically above an infinitely long superconducting strip. Using the Meissner effect of superconductors, we derive analytical expressions of the levitation forces acting on the dipole line. At lowest-order approximation, we discuss the possible application of our model system to estimate the upper limit of the levitation forces in some magnetic bearing systems. In one example, the model correctly calculated the vertical vibration frequency of an experimental superconducting bearing.

  8. Three-dimensionality of field-induced magnetism in a high-temperature superconductor

    DEFF Research Database (Denmark)

    Lake, B.; Lefmann, K.; Christensen, N.B.

    2005-01-01

    insulators, where each copper spin is antiparallel to its nearest neighbours(1), evolves into a fluctuating state where the spins show tendencies towards magnetic order of a longer periodicity. For certain charge-carrier densities, quantum fluctuations are sufficiently suppressed to yield static long......Many physical properties of high-temperature superconductors are two-dimensional phenomena derived from their square-planar CuO(2) building blocks. This is especially true of the magnetism from the copper ions. As mobile charge carriers enter the CuO(2) layers, the antiferromagnetism of the parent...

  9. Magnetic moment formation due to arsenic vacancies in LaFeAsO-derived superconductors.

    Science.gov (United States)

    Kikoin, Konstantin; Drechsler, Stefan-Ludwig; Koepernik, Klaus; Málek, Jiři; van den Brink, Jeroen

    2015-07-14

    Arsenic vacancies in LaFeAsO-derived superconductors are nominally non-magnetic defects. However, we find from a microscopic theory in terms of an appropriately modified Anderson-Wolff model that in their vicinity local magnetic moments form. They can arise because removing an arsenic atom breaks four strong, covalent bonds with the neighboring iron atoms. The moments emerging around an arsenic vacancy orient ferromagnetically and cause a substantial enhancement of the paramagnetic susceptibility in both the normal and superconducting state. The qualitative model description is supported by first principles band structure calculations of the As-vacancy related defect spectrum within a larger supercell.

  10. Ground state of an antiferromagnetic superconductor in the presence of a homogeneous magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Suzumura, Y.; Naji, A.D.S. (Waterloo Univ., Ontario (Canada). Dept. of Physics)

    1981-11-01

    The effect of a homogeneous magnetic field, H/sub 0/. on the ground state of an antiferromagnetic superconductor has been investigated. Assuming a one-dimensional like half-filled band, a new state has been found having gapless superconductivity and H/sub 0/-dependent order parameter. This state exists for Hsub(Q)/..delta../sub 0/ > 0.22 and when ..delta.. - Hsub(Q) <= H/sub 0/ < ..delta.. + Hsub(Q) Hsub(Q) is the staggered magnetic field, ..delta.. is the superconducting order parameter and ..delta../sub 0/ is ..delta.. in the absence of Hsub(Q) and H/sub 0/.

  11. Optical non-reciprocity in magnetic structures related to high-T_c superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Orenstein, Joseph W

    2011-06-02

    Rotation of the plane of polarization of reflected light (Kerr effect) is a direct manifestation of broken time reversal symmetry and is generally associated with the appearance of a ferromagnetic moment. Here I identify magnetic structures that may arise within the unit cell of cuprate superconductors that generate polarization rotation despite the absence of a net moment. For these magnetic symmetries the Kerr effect is mediated by magnetoelectric coupling, which can arise when antiferromagnetic order breaks inversion symmetry. The structures identifed are candidates for a time-reversal breaking phase in the pseudogap regime of the cuprates.

  12. Magnetizing properties of the commercial bulk superconductors; Shihan yo koon chodendo baruku no jika tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, H.; Fujinuma, S.; Noto, K. [Iwate Univ., Iwate (Japan); Murakami, M.; Yoshioka, J. [International Superconductivity Tech. Center, Tokyo (Japan); Chiba, T.

    2000-05-29

    It carries out the research in the high-temperature superconductor by many researchers, and it expects the practical application in tape wire rod, thin film and bulk material in various fields mainly on electric power application. Especially, it markets the high-temperature superconductivity bulk material for the application in the bulk material. It recently develops superconductive permanent magnet, which realized the temperature range of which superconducting characteristic using the high-temperature superconductivity bulk material is excellent using small refrigerating machine. Then, we evaluated the magnetization characteristic on the high-temperature superconductivity bulk material marketed. (NEDO)

  13. dc-magnetic-field dependence of the surface impedance of a multilayer superconductor system in the mixed state

    Science.gov (United States)

    Tagantsev, A. K.; Traito, K. B.

    1993-10-01

    We study the electrodynamics of a superlattice that consists of two kinds of layers: the layers of a type-II superconductor and the layers of a normal metal in a perpendicular magnetic field. The problem is treated in the framework of London electrodynamics taking into account simultaneously the nonlocality of the intervortex interaction and the Abrikosov vortex elasticity. The dependence of the surface impedance Z on the dc-magnetic-field induction BCB1/2 for large fields, the coefficients A and C being nonequal, with the crossover AB1/2-->CB1/2 at B~=Hc1. The type-(i) dependence characteristic of a uniform superconductor converts into a type-(ii) dependence as one diminishes the thickness of the superconductor layers. The physical origin of this conversion is explained. It is suggested that observed dependence in multilayer superconductor systems Z~B1/2 is due to the effect discussed in the paper.

  14. Trapped field measurements of Gd-Ba-Cu-O bulk superconductor in controlled pulse field magnetizing

    Energy Technology Data Exchange (ETDEWEB)

    Ida, T [Department of Electronic Control Engineering, Hiroshima National College of Maritime Technology, 4272-1, Higashino, Ohsakikamijima-cho, Toyota-gun, Hiroshima 725-0231 (Japan); Kimura, Y; Sano, T; Yamaguchi, K; Izumi, M [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan); Miki, M [Kitano Seiki Co. Ltd., 7-13-7, Chuo, Ohta-ku, Tokyo 143-0024 (Japan)], E-mail: ida@hiroshima-cmt.ac.jp

    2008-02-01

    For large-scale electric power application of the melt-processed high temperature superconductor (HTS) bulks, especially at rotating machine, development of trapping much higher magnetic fields by using pulsed magnetization technique is essential. It is difficult to use static field cooling (FCM) technique that is most effective magnetizing method for the general industrial HTS applications, because the FCM requires large-scale superconducting magnets. Because the rise in temperature due to the magnetic flux motion decreases the pinning force, we controlled the magnetic flux penetrating to the bulk for the effective magnetization. A couple of vortex-type copper coils applied a magnetic field to a Gd-Ba-Cu-O bulk, which dimension was 45mm in diameter and 19 mm in thickness. HTS bulk was magnetized by the controlled pulse field without passive LCR pulse. We controlled waveform by using the discharge current that IGBT chopper in pulse magnetizer intermitted. We applied the pulse magnetic field with the various risetime to the HTS bulk in liquid nitrogen. The various conditions of the controlled waveform pulse to trap well-dressed profile magnetized the Gd-Ba-Cu-O bulk, strongly at 77K. In the present study, we show several properties which was measured in the PFM of the HTS bulk.

  15. The fluctuation Hall conductivity and the Hall angle in type-II superconductor under magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Tinh, Bui Duc, E-mail: tinhbd@hnue.edu.vn [Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang (Viet Nam); Department of Physics, Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Hoc, Nguyen Quang; Thu, Le Minh [Department of Physics, Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Hanoi (Viet Nam)

    2016-02-15

    Highlights: • The time-dependent Ginzburg–Landau was used to calculate fluctuation Hall conductivity and Hall angle in type-II superconductor in 2D and 3D. • We obtain analytical expressions for the fluctuation Hall conductivity and the Hall angle summing all Landau levels without need to cutoff higher Landau levels to treat arbitrary magnetic field. • The results were compared to the experimental data on YBCO. - Abstract: The fluctuation Hall conductivity and the Hall angle, describing the Hall effect, are calculated for arbitrary value of the imaginary part of the relaxation time in the frame of the time-dependent Ginzburg–Landau theory in type II-superconductor with thermal noise describing strong thermal fluctuations. The self-consistent Gaussian approximation is used to treat the nonlinear interaction term in dynamics. We obtain analytical expressions for the fluctuation Hall conductivity and the Hall angle summing all Landau levels without need to cutoff higher Landau levels to treat arbitrary magnetic field. The results are compared with experimental data on high-T{sub c} superconductor.

  16. Theoretical approach to direct resonant inelastic X-ray scattering on magnets and superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Marra, Pasquale

    2015-10-26

    The capability to probe the dispersion of elementary spin, charge, orbital, and lattice excitations has positioned resonant inelastic X-ray scattering (RIXS) at the forefront of photon science. In this work, we will investigate how RIXS can contribute to a deeper understanding of the orbital properties and of the pairing mechanism in unconventional high-temperature superconductors. In particular, we show how direct RIXS spectra of magnetic excitations can reveal long-range orbital correlations in transition metal compounds, by discriminating different kind of orbital order in magnetic and antiferromagnetic systems. Moreover, we show how RIXS spectra of quasiparticle excitations in superconductors can measure the superconducting gap magnitude, and reveal the presence of nodal points and phase differences of the superconducting order parameter on the Fermi surface. This can reveal the properties of the underlying pairing mechanism in unconventional superconductors, in particular cuprates and iron pnictides, discriminating between different superconducting order parameter symmetries, such as s,d (singlet pairing) and p wave (triplet pairing).

  17. Persistent detwinning of EuFe{sub 2}As{sub 2} by small magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Maiwald, Jannis; Stingl, Christian; Bach, Nora; Jeevan, H.S.; Gegenwart, Philipp [Experimentalphysik VI, Universitaet Augsburg (Germany); Zapf, Sina; Jiang, Shuai; Neubauer, David; Loehle, Anja; Clauss, Conrad; Dressel, Martin [1. Physikalisches Institut, Universitaet Stuttgart (Germany); Post, Kirk; Basov, Dimitri [Department of Physics, UC San Diego (United States)

    2015-07-01

    The formation of twin domains in the orthorhombic phase of high-temperature superconductors is impeding the investigation of the in-plane anisotropy of these materials. Recently, we have shown how the brief application of a small magnetic field of ∝ 1 Tesla in the EuFe{sub 2}As{sub 2} iron pnictide leads to a substantial detwinning of the system, which is persistent up to the structural transition at ∝ 190 K even after the magnetic field has been switched off. This offers researchers the opportunity to investigate the detwinned iron arsenide without the application of any external symmetry breaking force, like the pressure of a mechanical clamp, or a magnetic field present during measurement. We will present angular dependent magnetoresistance, magnetostriction, thermal expansion and thermoelectric power measurements on the EuFe{sub 2}As{sub 2} parent compound as well as on various doped variants in order to shed further light on the mechanism behind the field induced detwinning, i.e. the interplay of the involved magnetic moments stemming form the Eu and Fe atoms in these compounds.

  18. Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors.

    Science.gov (United States)

    Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V

    2015-07-03

    The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm(2) cross-section. The impurities suppress superconductivity in a three-dimensional 'Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities.

  19. Performance of Magnetic-Superconductor Non-Contact Harmonic Drive for Cryogenic Space Applications

    Directory of Open Access Journals (Sweden)

    Jose Luis Perez-Diaz

    2015-07-01

    Full Text Available Harmonic drives are profusely used in aerospace mainly because of their compactness and large reduction ratio. However, their use in cryogenic environments is still a challenge. Lubrication and fatigue are non-trivial issues under these conditions. The objective of the Magnetic-Superconductor Cryogenic Non-contact Harmonic Drive (MAGDRIVE project, funded by the EU Space FP7, is to design, build, and test a new concept of MAGDRIVE. Non-contact interactions among magnets, soft magnetic materials, and superconductors are efficiently used to provide a high reduction ratio gear that smoothly and naturally operates at cryogenic environments. The limiting elements of conventional harmonic drives (teeth, flexspline, and ball bearings are substituted by contactless mechanical components (magnetic gear and superconducting magnetic bearings. The absence of contact between moving parts prevents wear, lubricants are no longer required, and the operational lifetime is greatly increased. This is the first mechanical reducer in mechanical engineering history without any contact between moving parts. In this paper, the test results of a −1:20 inverse reduction ratio MAGDRIVE prototype are reported. In these tests, successful operation at 40 K and 10−3 Pa was demonstrated for more than 1.5 million input cycles. A maximum torque of 3 N·m and an efficiency of 80% were demonstrated. The maximum tested input speed was 3000 rpm, six times the previous existing record for harmonic drives at cryogenic temperatures.

  20. Visualizing Majorana fermions in a chain of magnetic atoms on a superconductor

    Science.gov (United States)

    Yazdani, Ali

    2015-12-01

    A chain of magnetic atoms on the surface of a superconductor provides a versatile platform for realizing a one-dimensional topological superconductivity phase with edge-bounded Majorana fermions zero modes. This platform lends itself to spatial resolved measurements with scanning tunneling microscope (STM) that enables direct visualization of the presence of a localized Majorana zero mode. Experiments on self-assembled chains of Fe atoms on the surface of Pb show that such a system can be experimentally fabricated and studied using various high-resolution STM measurement techniques. Spatial and energy resolved STM experiments provide strong evidence for Majorana bound states that emerge due to the combination of Fe’s ferromagnetism and spin-orbit coupling of the superconducting Pb substrate. These studies provide a roadmap for optimizing topological superconductivity in this one-dimensional platform and its extension to realize chiral two-dimensional superconductors.

  1. Signature of magnetic-dependent gapless odd frequency states at superconductor/ferromagnet interfaces.

    Science.gov (United States)

    Di Bernardo, A; Diesch, S; Gu, Y; Linder, J; Divitini, G; Ducati, C; Scheer, E; Blamire, M G; Robinson, J W A

    2015-01-01

    The theory of superconductivity developed by Bardeen, Cooper and Schrieffer (BCS) explains the stabilization of electron pairs into a spin-singlet, even frequency, state by the formation of an energy gap within which the density of states is zero. At a superconductor interface with an inhomogeneous ferromagnet, a gapless odd frequency superconducting state is predicted, in which the Cooper pairs are in a spin-triplet state. Although indirect evidence for such a state has been obtained, the gap structure and pairing symmetry have not so far been determined. Here we report scanning tunnelling spectroscopy of Nb superconducting films proximity coupled to epitaxial Ho. These measurements reveal pronounced changes to the Nb subgap superconducting density of states on driving the Ho through a metamagnetic transition from a helical antiferromagnetic to a homogeneous ferromagnetic state for which a BCS-like gap is recovered. The results prove odd frequency spin-triplet superconductivity at superconductor/inhomogeneous magnet interfaces.

  2. Higgs mechanism in three-dimensional topological superconductors and anomalous Hall effect in zero magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, Flavio; Eremin, Ilya [Theoretische Physik III, Ruhr-Universitaet Bochum (Germany)

    2015-07-01

    We discuss the peculiar nature of Higgs mechanism in an effective field theory for three-dimensional topological superconductors. The effective theory features two order parameters associated to the two chiral fermion species in the system. The resulting electrodynamics of such a topological superconductor exhibits a topological magnetoelectric effect with an axion field given by the phase difference of the order parameters. As consequence, the London regime is highly non-linear and anomalous Hall effect in the absence of an external magnetic field occurs. In this anomalous Hall effect the generated current transverse to an applied electric field changes sign with the temperature. We also discuss the scaling behavior of the penetration depth near the transition temperature, which is also shown to exhibit a scaling exponent that is crucially influenced by the axion term, varying continuously as function of the average phase difference.

  3. Transverse voltage in superconductors at zero applied magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Luz, M.S. da [Escola de Engenharia de Lorena - USP, P.O. Box 116, Lorena, SP 12602-810 (Brazil)], E-mail: luz@physics.montana.edu; Santos, C.A.M. dos; Shigue, C.Y.; Carvalho, F.J.H. de; Machado, A.J.S. [Escola de Engenharia de Lorena - USP, P.O. Box 116, Lorena, SP 12602-810 (Brazil)

    2009-01-01

    A systematic study of the transverse voltage at zero magnetic field in the superconducting state is reported. The effects of warming rate, temperature, applied magnetic field, and electrical current on the transversal resistance (R{sub XY}) of polycrystalline superconducting sample are taken into account. At zero magnetic field two peaks are observed in R{sub XY}(T) curves which are related to the double superconducting transition in the R{sub XX}(T) component. In the superconducting (R{sub XX} = zero) and normal states no transverse voltage has been detected at zero magnetic field as expected. The results are discussed within the framework of the motion of Abrikosov and Josephson vortices and anti-vortices. A new scaling relation between transverse and longitudinal components given by R{sub XY} {approx} dR{sub XX}/dT has been confirmed.

  4. Dependence of levitation force on frequency of an oscillating magnetic levitation field in a bulk YBCO superconductor

    Science.gov (United States)

    Carter, Hamilton; Pate, Stephen; Goedecke, George

    2013-02-01

    The dependence of the magnetic field strength required for levitation of a melt textured, single domain YBCO superconductor disk on the frequency of the current generating the levitating magnetic field has been investigated. The magnetic field strength is found to be independent of frequency between 10 and 300 Hz. This required field strength is found to be in good experimental and theoretical agreement with the field strength required to levitate the same superconductor with a non-oscillating magnetic field. Hysteretic losses within the superconductor predicted by Bean’s critical-state model were also calculated. The measured data rules out any significant Bean’s model effects on the required levitation field strength within the measured frequency range.

  5. Magnetic separation using high-T sub c superconductors

    CERN Document Server

    Bolt, L

    2001-01-01

    sensitivity of the high-T sub c material to magnetic fields. Finite elements modelling of the system has provided the framework for the quantitative analysis of the magnetic field distributions on the coil windings and the optimisation of the system configuration. The performance of the separator has been tested at 77 K with liquid nitrogen at atmospheric pressure, and at a temperature approx = 67 K by pumping liquid nitrogen at a pressure around 100 Torr. The highest field obtained in the air gap at 67 K was of 340 mT. Magnetic separators with an iron circuit have been in operation for many years in mineral industry, and there appear to be an opportunity of building machines with high-T sub c coils or retrofitting existing machines with high-T sub c coils to run them closer to saturation in a cheap and effective way. Superconductivity has found in magnetic separation one of its major industrial applications second only to magnetic resonance imaging. Low-T sub c superconducting coils have been employed in Hig...

  6. Magnetization of Multifilamentary Superconductor Nb3Sn in Perpendicular Field

    Institute of Scientific and Technical Information of China (English)

    LIU Fang; WENG Peide; WU Yu; LONG Feng

    2008-01-01

    Hysteresis loss is one of the electromagnetic characteristics controlled by time evo-lution of magnetic field and current distribution inside the conductor. Brandt's method allows us to model the interaction of the conductor with an external magnetic field. Instead of the constant critical current density (Jc =CONST), the Jc scaling law from current-voltage (I-V) measurement is used to model the magnetization loop. By comparing the calculated results with the measured data, it is shown that the Jc scaling law, i.e. the deviatoric strain model, is not useful in a very low field. To solve this problem, the Kim model about Jc as a function of applied field has been applied in the low field case. This method can be used to predict the hysteresis loss of Nb3Sn filamentary strand.

  7. Magnetic coupling by using levitation characteristics of YBCO superconductors

    Science.gov (United States)

    Ishigaki, H.; Ito, H.; Itoh, M.; Hida, A.; Takahata, R.

    1993-03-01

    A mechanical system which uses high lateral restoring forces of high-Tc materials as the driving force for a magnetic coupling is proposed. As the basic study of the superconducting magnetic coupling, the relationship between the lateral restoring force and levitation force, transmitted torque characteristics as a function of a twisting angle and clearance, and damping characteristics of the coupling were examined. Superiorities of the coupling such as high damping coefficients and high stability against time and twisting angle were revealed. A magnetic force sensor system was used to evaluate the superconducting characteristics of materials, and nonuniform distribution of repulsive force was observed for the YBCO pellet fabricated by the melt-powder-melt-growth process. The improvement of the homogeneity was achieved by compensating for the composition rate which had changed during the quenching process.

  8. Magnetic relaxation induced by transverse flux shaking in MgB2 superconductors

    Science.gov (United States)

    Luzuriaga, J.; Badía-Majós, A.; Nieva, G.; Giordano, J. L.; López, C.; Serquis, A.; Serrano, G.

    2009-01-01

    We report on measurements and numerical simulations of the behavior of MgB2 superconductors when magnetic field components are applied along mutually perpendicular directions. By closely matching the geometry in simulations and measurements, full quantitative agreement is found. The critical state theory and a single phenomenological law, i.e. the field dependence of the critical current density Jc(B), are sufficient for a full quantitative description of the measurements. These were performed in thick strips of carbon nanotube doped MgB2 samples. Magnetization was measured in two orthogonal directions using a SQUID magnetometer. Magnetic relaxation effects induced by the application of an oscillatory perpendicular field were observed and simulated numerically. The measurements confirm the numerical predictions, that two relaxation regimes appear, depending on the amplitude of the applied magnetic field. The overall agreement constitutes a convincing validation of the critical state model and the numerical procedures used.

  9. Status of high temperature superconductor based magnets and the conductors they depend upon

    CERN Document Server

    Schwartz, J; Chan, W K; Gou, X F; Liu, X T; Phillips, M; Le, Q V; Naderi, G; Turenne, M; Ye, L

    2011-01-01

    This paper reviews the status of high temperature superconductors for high field magnets for future devices such as a high energy LHC or a muon collider. Some of the primary challenges faced for the implementation of systems are discussed. Two conductor technologies, Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ and YBa$_2$Cu$_3$O$_{7-\\delta}$, have emerged as high field conductor options, but their relative advantages and disadvantages for high field magnets are quite different. These are reviewed from an engineering perspective, including coil manufacturing, electromechanical behaviour and quench behaviour. Lastly, the important roles of "system pull" upon conductor and magnet technology development, and of interactions between the materials and magnet communities for accelerating development, are discussed.

  10. Two magnetic Grüneisen parameters in the ferromagnetic superconductor UGe2

    Science.gov (United States)

    Hardy, F.; Meingast, C.; Taufour, V.; Flouquet, J.; v. Löhneysen, H.; Fisher, R. A.; Phillips, N. E.; Huxley, A.; Lashley, J. C.

    2009-11-01

    We report ambient-pressure magnetization, heat capacity, and thermal-expansion measurements of the ferromagnetic superconductor UGe2 in high magnetic fields. An analysis of the magnetic heat capacity derived from both magnetization and specific-heat data shows that UGe2 is well described in the framework of the molecular-field theory. Our heat-capacity and thermal-expansion results reveal a clear crossover regime, a feature that illustrates the proximity to the quantum critical end point of a first-order boundary between two different ferromagnetic phases. Furthermore, we show that the ferromagnetic contribution to these thermodynamic quantities can be split into two terms with distinct Grüneisen parameters.

  11. Impurity- and magnetic-field-induced quasiparticle states in chiral p-wave superconductors

    Science.gov (United States)

    Guo, Yao-Wu; Li, Wei; Chen, Yan

    2017-10-01

    Both impurity- and magnetic-field-induced quasiparticle states in chiral p-wave superconductors are investigated theoretically by solving the Bogoliubov-de Gennes equations self-consistently. At the strong scattering limit, we find that a universal state bound to the impurity can be induced for both a single nonmagnetic impurity and a single magnetic impurity. Furthermore, we find that different chiral order parameters and the corresponding supercurrents have uniform distributions around linear impurities. Calculations of the local density of states in the presence of an external magnetic field show that the intensity peak of the zero-energy Majorana mode in the vortex core can be enhanced dramatically by tuning the strength of the external magnetic field or pairing interaction.

  12. A note on magnetization of high temperature superconductors (YBCO, BSCCO) in mixed state

    Energy Technology Data Exchange (ETDEWEB)

    Kalta, B. [Department of Physics, Sonepur College, Subarnapur 767 017 (India); Pattanaik, A., E-mail: phyanup@gmail.com [P.G. Department of Physics, Sambalpur University, JV, Burla 768 019 (India); Nayak, P. [P.G. Department of Physics, Sambalpur University, JV, Burla 768 019 (India); Nanda, K.K. [Material Research Centre, Indian Institute of Sciences, Bangalore (India)

    2011-12-15

    Vortex overlapping has a prominent role in magnetism. M(H) shows linear dependence with vortex overlapping mechanism for YBCO compound. Magnetization in the reversible region. Effective penetration depth due to vortex overlapping. We present a critical study of the temperature and field dependence magnetization of high temperature superconductors (HTSCs). The controversial field dependence of dM/d ln B for YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (BSCCO) is discussed using different models. Moreover, for both the systems the magnetization (M(H)) dependence is compared with field (H) dependence.

  13. Magnetic excitations in the ferromagnetic superconductor UGe2 under pressure

    Science.gov (United States)

    Kepa, M. W.; Sokolov, D. A.; Böhm, M.; Huxley, A. D.

    2014-12-01

    Ferromagnetism and superconductivity coexist in UGe2 under pressures in the range of 10-16 kbar. Here, equal spin electrons are paired to give a spin triplet state but the pairing mechanism is still not verified experimentally. The work presented here attempts to verify whether the longitudinal magnetic fluctuations associated with a magnetic transition within the ferromagnetic state might be responsible for the electron pairing. We show that the energy scale of these fluctuations must be smaller than those associated with the second order phase transition at the Curie temperature. Furthermore, there is no significant change of the energy scale of the fluctuations at the Curie temperature as a function of pressure.

  14. Levitation force and magnetization in bulk and thin film high T{sub c} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    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{sub 2}Cu{sub 3}O{sub 7-{delta}} 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{sub 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{sub 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{sub 2}Cu{sub 3}O{sub 7-{delta}} 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

  15. Magnetic field expulsion in superconducting granular ceramics and in polymer/superconductor composites

    Energy Technology Data Exchange (ETDEWEB)

    Benlhachemi, A. [Univ. de Toulon et du Var, La Garde (France). Lab. des Materiaux Multiphases et Interfaces]|[Lab. de Chimie des Solides, Faculte des Sciences, Univ. Ibnou Zohr, Agadir (Morocco); Fremy, M.A.; Breandon, C.; Tatarenko, H.; Gavarri, J.R. [Univ. de Toulon et du Var, La Garde (France). Lab. des Materiaux Multiphases et Interfaces; Benyaich, H. [Lab. de Chimie des Solides, Faculte des Sciences, Univ. Ibnou Zohr, Agadir (Morocco)

    1998-05-01

    The magnetic interaction between a permanent magnet and superconducting ceramics such as YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub (10+} {sub de} {sub lta)} depend on the superconducting state of each phase and on the junctions between grains. In the case of polymer/superconductor composites, screening effects depend on the volume fraction of superconductor. Measurements of the evolution of the levitation force (F=A/d{sup {gamma}}) as a function of the interaction distance d are used to characterize the effective response of the ceramics or composites to the magnetic flux penetration. Some of the abnormal variations of the exponent {gamma} and of the term A (in F=A/d{sup {gamma}}) could be reinterpreted in terms of a change in superconducting regime. Other observed variations of {gamma} should be due to the variation of the effective field from the cylindrical magnet. (orig.) 19 refs.

  16. Investigation on stresses of superconductors under pulsed magnetic fields based on multiphysics model

    Science.gov (United States)

    Yang, Xiaobin; Li, Xiuhong; He, Yafeng; Wang, Xiaojun; Xu, Bo

    2017-04-01

    A multiphysics model for the numerical computation of stresses, trapped field and temperature distribution of a infinite long superconducting cylinder is proposed, based on which the stresses, including the thermal stresses and mechanical stresses due to Lorentz force, and trapped fields in the superconductor subjected to pulsed magnetic fields are analyzed. By comparing the results under pulsed magnetic fields with different pulse durations, it is found that the both the mechanical stress due to the electromagnetic force and the thermal stress due to temperature gradient contribute to the total stress level in the superconductor. For pulsed magnetic field with short durations, the thermal stress is the dominant contribution to the total stress, because the heat generated by AC-loss builds up significant temperature gradient in such short durations. However, for a pulsed field with a long duration the gradient of temperature and flux, as well as the maximal tensile stress, are much smaller. And the results of this paper is meaningful for the design and manufacture of superconducting permanent magnets.

  17. Cooling achieved by rotating an anisotropic superconductor in a constant magnetic field: A new perspective

    Directory of Open Access Journals (Sweden)

    Manh-Huong Phan

    2016-12-01

    Full Text Available A new type of rotary coolers based on the temperature change (ΔTrot of an anisotropic superconductor when rotated in a constant magnetic field is proposed. We show that at low temperature the Sommerfeld coefficient γ(B,Θ of a single crystalline superconductor, such as MgB2 and NbS2, sensitively depends on the applied magnetic field (B and the orientation of the crystal axis (Θ, which is related to the electronic entropy (SE and temperature (T via the expression: SE=γT. A simple rotation of the crystal from one axis to one another in a constant magnetic field results in a change in γ and hence SE: ΔSE=ΔγT. A temperature change −ΔTrot ∼ 0.94 K from a bath temperature of 2.5 K is achieved by simply rotating the single crystal MgB2 by 90° with respect to the c-axis direction in a fixed field of 2 T. ΔTrot can be tuned by adjusting the strength of B within a wide magnetic field range. Our study paves the way for development of new materials and cryogenic refrigerators that are potentially more energy-efficient, simplified, and compact.

  18. Effect of reciprocating motions around working points on levitation force of superconductor-magnet system

    Science.gov (United States)

    Xu, Jimin; Zhang, Fei; Sun, Tao; Yuan, Xiaoyang; Zhang, Cuiping

    2016-09-01

    In order to simulate vibration around working points in practical operation of superconducting levitation system, magnet in a simple superconductor-magnet system are conducted reciprocating motions around static height in this study. Two YBCO cylindrical samples with different grain orientations are used to investigate the effect of reciprocating motions of magnet on superconducting magnetic force. The c-axis of sample S1 is perpendicular to the top surface while sample S2 is parallel to the top surface. The initial cooling processes for the superconductors include zero-field-cooled (ZFC) and filed-cooled (FC). Compared to the levitation force before reciprocating motions, the ZFC levitation force at static height becomes smaller after reciprocating while the FC force presents opposite phenomenon. It is found that levitation force at static height tends to be stable after several times of reciprocating under ZFC and FC conditions and its time-decay phenomenon is suppressed in some extent, which is meaningful for the practical application of superconducting levitation system. Based on vortex dynamic, some physical discussions are presented to the experimental results.

  19. Hysteretic ac losses in a superconductor strip between flat magnetic shields

    Energy Technology Data Exchange (ETDEWEB)

    Genenko, Y A; Rauh, H, E-mail: hera@tgm.tu-darmstadt.d [Institut fuer Materialwissenschaft, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany)

    2010-07-15

    Hysteretic ac losses in a thin, current-carrying superconductor strip located between two flat magnetic shields of infinite permeability are calculated using Bean's model of the critical state. Exact numerical calculations and approximate analytical forms delineating the penetration of magnetic flux and the energy dissipated during a cycle of the ac transport current, per unit length of the strip, are derived. For the shields oriented parallel to the plane of the strip, the penetration of the self-induced magnetic field is found to be enhanced, with the analytical current dependence of the ac loss conditionally resembling that of an isolated superconductor slab; for the shields oriented perpendicular to the plane of the strip, the penetration of the self-induced magnetic field is found to be impaired, with the analytical current dependence of the ac loss conditionally duplicating that of a regular set of curved superconducting tapes extending longitudinally around a surface of cylindrical shape. Thus, hysteretic ac losses can strongly augment or, respectively, wane when the shields approach the strip.

  20. Study of magnetic bearings with high temperature superconductors, phase 3

    Science.gov (United States)

    Eyssa, Y. M.; Huang, X.

    1991-01-01

    Three areas related to the actively controlled radial magnetic bearing concepts are discussed. These areas are: (1) modification to the ac loss calculations of the 1990 report; (2) a continuous changing mechanism to compensate rotor current drop due to ac losses; and (3) design of a proof of principle experiment simulating the proposed bearing concept.

  1. Superconductor Dynamics

    CERN Document Server

    Gömöry, F

    2014-01-01

    Superconductors used in magnet technology could carry extreme currents because of their ability to keep the magnetic flux motionless. The dynamics of the magnetic flux interaction with superconductors is controlled by this property. The cases of electrical transport in a round wire and the magnetization of wires of various shapes (circular, elliptical, plate) in an external magnetic field are analysed. Resistance to the magnetic field penetration means that the field produced by the superconducting magnet is no longer proportional to the supplied current. It also leads to a dissipation of electromagnetic energy. In conductors with unequal transverse dimensions, such as flat cables, the orientation with respect to the magnetic field plays an essential role. A reduction of magnetization currents can be achieved by splitting the core of a superconducting wire into fine filaments; however, new kinds of electrical currents that couple the filaments consequently appear. Basic formulas allowing qualitative analyses ...

  2. Studies of the gap structure of iron-based superconductors using magnetic penetration depth

    Science.gov (United States)

    Carrington, Antony

    2011-06-01

    This article reviews experiments to determine the structure of the superconducting gap in the iron-based superconductors. It focuses on insights provided by measurements of the temperature dependence of magnetic penetration depth but also discusses the information provided by other measurements especially thermal conductivity. The article includes background theory on the types of gap structure suggested for the iron-based superconductors as well as the general theory of penetration depth in conventional and unconventional superconductors. The effect of impurity scattering on each candidate gap structure is important for the interpretation of data and so will also be discussed. Penetration depth data for single crystals of the following compounds is reviewed: SmFeAsO 0.8F 0.2, FeTe 0.5Se 0.5, LaFePO, KFe 2As 2 and BaFe 2(As 0.67P 0.33) 2 along with discussion on related materials such as K- and Co-doped BaFe 2As 2.

  3. Studying the kinetics of magnetization in high Tc superconductors

    Science.gov (United States)

    Turchinskaya, Marina

    1993-01-01

    The first microscopic maps of magnetic induction in YBa2Cu3O(7-x) crystals which directly show the dependence of flux flow on twin density and polytwin block and twin boundary orientation are reported. These maps were obtained by means of a recently-improved magneto-optical imaging technique. Pinning was lowest in untwinned regions and increased with increasing twin density. An isotropy in twin boundary pinning, defined as the ratio of the magnetic induction gradient across twin boundaries to that along twin boundaries, was 10 at 17 K; this ratio increased with increasing temperature. In polycrystals, twin boundaries also had a strongly anisotropic effect on flux flow into a grain from a grain boundary.

  4. Penetration dynamics of a magnetic field pulse into high-? superconductors

    Science.gov (United States)

    Meerovich, V.; Sinder, M.; Sokolovsky, V.; Goren, S.; Jung, G.; Shter, G. E.; Grader, G. S.

    1996-12-01

    The penetration of a magnetic field pulse into a high-0953-2048/9/12/004/img9 superconducting plate is investigated experimentally and theoretically. It follows from our experiments that the threshold of penetration increases with increasing amplitude and/or decreasing duration of the applied pulse. The penetrating field continues to grow as the applied magnetic field decreases. The peculiarities observed are explained in the framework of the extended critical state model. It appears that the deviations from Bean's classical critical state model are characterized by a parameter equal to the square of the ratio of plate thickness to skin depth. The applicability of the classical critical state model is restricted by the condition that this parameter is much less than 1. This condition is also the criterion for the applicability of pulse methods of critical current measurements.

  5. Comparison of simulation and experiment on levitation force between GdBCO bulk superconductor and superconducting magnet

    Energy Technology Data Exchange (ETDEWEB)

    Araki, S., E-mail: satoshi@sum.sd.keio.ac.j [Department of System Design Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Nagashima, K.; Seino, H. [Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji, Tokyo 185-8540 (Japan); Murakami, T.; Sawa, K. [Department of System Design Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

    2009-10-15

    High temperature bulk superconductors have significant potential for various engineering applications such as a flywheel energy storage system. This system is expected to decrease the energy loss by using bulk superconductors for the bearing. Recently, the authors have developed a new superconducting magnet to realize large levitation force. In this system, the axial component of magnetic field is canceled each other but the radial component of magnetic field expects to be enhanced. Thus, it was expected that the large levitation force can be realized and its time relaxation will be decreased. And in the previous paper, the levitation force and its time relaxation were measured under the various conditions by using this new magnet. But it is difficult to consider what phenomenon has happened in the bulk from only experimental results. In addition the quantitative evaluation cannot be done only by the experimental results, for example, the influence of the magnetic field penetration and magnetic distribution around a bulk superconductor on the maximum force and so on. Thus, in this paper, the authors simulated the levitation force of bulk superconductor by using ELF/MAGIC, which is a three-dimensional electromagnetic analytical software. In the simulation the bulk was considered as a rigid body and the simulation was executed under the same conditions and model with the experiment. The distribution of magnetic field and the levitation force were obtained and discussed.

  6. A Cryogenic Magnetostrictive Actuator using a Persistent High Temperature Superconducting Magnet, Part 1: Concept and Design. Part 1; Concept and Design

    Science.gov (United States)

    Horner, Garnett C.; Bromberg, Leslie; Teter, J. P.

    2001-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications, such as Next Generation Space Telescope (NGST), the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Very fast charging and discharging of HTS tubes, as short as 100 microseconds, has been demonstrated. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSSCO 2212 with a

  7. Persistent optically induced magnetism in oxygen-deficient strontium titanate.

    Science.gov (United States)

    Rice, W D; Ambwani, P; Bombeck, M; Thompson, J D; Haugstad, G; Leighton, C; Crooker, S A

    2014-05-01

    Strontium titanate (SrTiO3) is a foundational material in the emerging field of complex oxide electronics. Although its bulk electronic and optical properties are rich and have been studied for decades, SrTiO3 has recently become a renewed focus of materials research catalysed in part by the discovery of superconductivity and magnetism at interfaces between SrTiO3 and other non-magnetic oxides. Here we illustrate a new aspect to the phenomenology of magnetism in SrTiO3 by reporting the observation of an optically induced and persistent magnetization in slightly oxygen-deficient bulk SrTiO3-δ crystals using magnetic circular dichroism (MCD) spectroscopy and SQUID magnetometry. This zero-field magnetization appears below ~18 K, persists for hours below 10 K, and is tunable by means of the polarization and wavelength of sub-bandgap (400-500 nm) light. These effects occur only in crystals containing oxygen vacancies, revealing a detailed interplay between magnetism, lattice defects, and light in an archetypal complex oxide material.

  8. Persistence of slow fluctuations in the overdoped regime of Ba(Fe1-xRhx)2As2 superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bossoni, L. [Univ. of Pavia (Italy); Leiden Univ. (Netherlands); Moroni, M. [Univ. of Pavia (Italy); Julien, M. H. [Leiden Univ. (Netherlands); Canfield, Paul C. [Ames Lab. and Iowa State Univ., Ames, IA (United States); Mayaffre, H. [Leiden Univ. (Netherlands); Reyes, A. [National High Magnetic Field Lab., Tallahassee, FL (United States); Halperin, W. P. [Northwestern Univ., Evanston, IL (United States); Carretta, P. [Univ. of Pavia (Italy)

    2016-04-15

    We present nuclear magnetic resonance evidence that very slow (1 MHz) spin fluctuations persist into the overdoped regime of Ba(Fe1-xRhx)2As2 superconductors. Measurements of the 75As spin echo decay rate, obtained both with Hahn Echo and Carr Purcell Meiboom Gill pulse sequences, show that the slowing down of spin uctuations can be described by short-range diffusive dynamics, likely involving domain walls motions separating (π/a, 0) from (0, π/a) correlated regions. This slowing down of the fluctuations is weakly sensitive to the external magnetic field and, although fading away with doping, it extends deeply into the overdoped regime.

  9. Effects of strong magnetic fields on pairing fluctuations in high-temperature superconductors

    OpenAIRE

    Eschrig, Matthias; Rainer, D.; Sauls, J. A.

    1999-01-01

    We present the theory for the effects of superconducting pairing fluctuations on the nuclear spin-lattice relaxation rate 1/T1 and the NMR Knight shift for layered superconductors in high magnetic fields. These results can be used to clarify the origin of the pseudogap in high-Tc cuprates, which has been attributed to spin fluctuations as well as pairing fluctuations. We present theoretical results for s-wave and d-wave pairing fluctuations and show that recent experiments in optimally doped ...

  10. Interaction of ultra soft magnetic materials with the high-T{sub c} superconductor YBCO

    Energy Technology Data Exchange (ETDEWEB)

    Stahl, Claudia; Treiber, Sebastian; Schuetz, Gisela [Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart (Germany); Walker, Patrick [Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart (Germany); Aalen University, Beethovenstrasse 1, 73430 Aalen (Germany); Albrecht, Joachim [Aalen University, Beethovenstrasse 1, 73430 Aalen (Germany)

    2013-07-01

    We have grown bilayers of optimally doped YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) and ferromagnetic CoFeB on single-crystalline substrates by pulsed laser deposition and sputtering. These heterostructures are typically composed of about 100 nm YBCO and several 10 nm of CoFeB. Regarding the superconductor, the properties of the YBCO film change as a consequence of the vicinity of the ferromagnet. In detail we investigated the critical current density as a function of temperature, applied field and time as well as the transition temperature by SQUID magnetization measurements and quantitative magneto-optical measurements. The amorphous material CoFeB exhibits an in plane anisotropy and a very low coercivity. From magneto-optical images we find that the flux line lattice of the superconductor is mapped into the magnet and still visible as significant magnetic out-of-plane contrast at room temperature. We discuss this phenomenon as a new route to high-resolution mapping of the flux line distribution on a nanometer scale.

  11. Characterisation of practical high temperature superconductors in pulsed magnetic fields and development of associated technology

    CERN Document Server

    Saleh, P M

    2000-01-01

    including a innovative design of a 100ms pulsed magnet solenoid. Critical current measurements on state of the art practical high temperature superconductors are presented. Bi sub 2 Sr sub 2 CaCu sub 2 O silver-alloy matrix powder-in-tube and silver-alloy substrate dip-coated tapes, formed into various geometries, have been tested in pulsed magnetic fields of various pulse lengths. These measurements have been compared to tests performed in continuous magnetic fields. A distinct discrepancy between pulsed and continuous measurements has been observed in these silver-alloy, high temperature superconductor composites. The critical current measured in pulsed fields is depressed compared to those measured in continuous fields. Evidence is provided to strongly suggest that eddy current heating in the silver-alloy substrate/sheath of the conductor is responsible for this discrepancy. A model is presented to predict the temperature rise due to eddy current heating. This model shows good agreement with observations. ...

  12. 2000 Lilienfeld Prize Talk - From Model Magnets to High Temperature Superconductors

    Science.gov (United States)

    Birgeneau, Robert J.

    2000-03-01

    Magnetic materials often provide simple and clean examples of important problems in statistical physics. In recent years, much attention has been focussed on one and two dimensional Heisenberg spin systems in which quantum fluctuations play an essential role. Of particular interest are the two dimensional CuO2 Heisenberg square lattice antiferromagnets which, on doping with holes or electrons, become high temperature superconductors. We will review the results of experiments and quantum Monte Carlo calculations on one and two dimensional quantum magnets. We shall also discuss recent neutron studies of the novel incommensurate magnetic structures that occur in the spin glass and superconducting phases of the doped La2CuO4 system. We shall emphasize, in particular, the newly discovered one dimensional spin modulations in the spin glass phase together with the reorientation transition which coincides with the insulator to superconducting transition.

  13. Flux motion in Y-Ba-Cu-O bulk superconductors during pulse field magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Yoshizawa, K [Department of Physics, College of Humanities and Sciences, Nihon University, 3-25-40 Sakura-Josui, Setagaya-ku, Tokyo 156-8550 (Japan); Nariki, S [Division of Material Science and Physics, Bulk Superconductor Laboratory, 1-16-25 Shibaura, Minato-ku, Tokyo 105-0023 (Japan); Sakai, N [Division of Material Science and Physics, Bulk Superconductor Laboratory, 1-16-25 Shibaura, Minato-ku, Tokyo 105-0023 (Japan); Murakami, M [Division of Material Science and Physics, Bulk Superconductor Laboratory, 1-16-25 Shibaura, Minato-ku, Tokyo 105-0023 (Japan); Hirabayasi, I [Division of Material Science and Physics, Bulk Superconductor Laboratory, 1-16-25 Shibaura, Minato-ku, Tokyo 105-0023 (Japan); Takizawa, T [Department of Physics, College of Humanities and Sciences, Nihon University, 3-25-40 Sakura-Josui, Setagaya-ku, Tokyo 156-8550 (Japan)

    2004-02-01

    We have studied the relationship between the magnetization and temperature change in Y-Ba-Cu-O bulk superconductor during pulse field magnetization (PFM). The flux motion was monitored using both Hall sensors and pick-up coils that are placed on a surface of a Y-Ba-Cu-O disc having dimensions of 15 mm in diameter and 0.95 mm in thickness. The peak value of the field was varied from 0.2 to 0.8 T. The effect of the static bias field was also studied in the range of 0-3 T. The temperature of the sample surface was measured using a resistance temperature sensor. The temperature increased with the magnitude of the applied pulsed magnetic field, and the amount of temperature rise decreased with increasing static bias field.

  14. Finite-size-induced stability of a permanent magnet levitating over a superconductor in the Meissner state

    Science.gov (United States)

    Perez-Diaz, Jose Luis; Garcia-Prada, Juan Carlos

    2007-10-01

    The force between a magnetic dipole and a finite superconductor in the Meissner state (Hsuperconductor therefore suffices to explain a stability for the levitation of a magnet over it or even the suspension of one of them under the other one. This does not contradict the existence of flux penetration. However, this makes the flux penetration not necessary to explain both stability and attractiveness, as has been assumed until now.

  15. Do Superconductors Have Zero Resistance in a Magnetic Field?

    Energy Technology Data Exchange (ETDEWEB)

    Strachan, D. R.; Sullivan, M. C.; Fournier, P.; Pai, S. P.; Venkatesan, T.; Lobb, C. J.

    2001-08-06

    We show that dc voltage versus current measurements of a YBa{sub 2}Cu {sub 3}O{sub 7-{delta}} film in a magnetic field can be collapsed onto scaling functions proposed by Fisher et al.[Phys.Rev.B 43, 130 (1991)] as is widely reported in the literature. We find, however, that good data collapse is achieved for a wide range of critical exponents and temperatures. These results strongly suggest that agreement with scaling alone does not prove the existence of a phase transition. We propose a criterion to determine if the data collapse is valid, and thus if a phase transition occurs. To our knowledge, none of the data reported in the literature meet our criterion.

  16. Superconductor-Mediated Modification of Gravity? AC Motor Experiments with Bulk YBCO Disks in Rotating Magnetic Fields

    Science.gov (United States)

    Noever, David A.; Koczor, Ronald J.; Roberson, Rick

    1998-01-01

    We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. Podkietnov, et al (Podkietnov, E. and Nieminen, R. (1992) A Possibility of Gravitational Force Shielding by Bulk YBa2 Cu3 O7-x Superconductor, Physica C, C203:441-444.) have indicated that rotating AC fields play an essential role in their observed distortion of combined gravity and barometric pressure readings. We report experiments on large (15 cm diameter) bulk YBCO ceramic superconductors placed in the core of a three-phase, AC motor stator. The applied rotating field produces up to a 12,000 revolutions per minute magnetic field. The field intensity decays rapidly from the maximum at the outer diameter of the superconducting disk (less than 60 Gauss) to the center (less than 10 Gauss). This configuration was applied with and without a permanent DC magnetic field levitating the superconducting disk, with corresponding gravity readings indicating an apparent increase in observed gravity of less than 1 x 10(exp -6)/sq cm, measured above the superconductor. No effect of the rotating magnetic field or thermal environment on the gravimeter readings or on rotating the superconducting disk was noted within the high precision of the observation. Implications for propulsion initiatives and power storage flywheel technologies for high temperature superconductors will be discussed for various spacecraft and satellite applications.

  17. Magnetic-Field-Enhanced Incommensurate Magnetic Order in the Underdoped High-Temperature Superconductor YBa2Cu3O6.45

    DEFF Research Database (Denmark)

    Haug, D.; Hinkov, V.; Suchaneck, A.

    2009-01-01

    We present a neutron-scattering study of the static and dynamic spin correlations in the underdoped high-temperature superconductor YBa2Cu3O6.45 in magnetic fields up to 15 T. The field strongly enhances static incommensurate magnetic order at low temperatures and induces a spectral-weight shift...

  18. Force between a magnetic tip and an inhomogeneous superconductor at zero field

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, Gilson, E-mail: gmc@if.ufrj.b [Instituto de Fisica, Universidade Federal do Rio de Janeiro, C.P. 68528, 21941-972, Rio de Janeiro-RJ (Brazil)

    2010-10-01

    The force exerted by a semi-infinite inhomogeneous superconductor with a planar interface to vacuum on a magnetic tip is studied theoretically in the absence of external magnetic fields. It is shown that the force has a contribution from inhomogeneities due to material defects with unique characteristics. Defects are taken into account in the London limit by allowing the mass parameter to vary spatially. The contribution from defects to the force is calculated analytically to first order in the deviation of the mass parameter from its constant value for the homogeneous superconductor, assuming that the tip is a point dipole perpendicular to the interface, and that it does not spontaneously create vortex matter. Random point defects and linear localized defects are considered phenomenologically. For each defect type the force dependence on the dipole position coordinates is obtained, and the force magnitudes are estimated numerically. The predictions for the dependence of the linear defect force on the dipole lateral position are found to agree qualitatively with experiment.

  19. Kramers non-magnetic superconductivity in LnNiAsO superconductors.

    Science.gov (United States)

    Li, Yuke; Luo, Yongkang; Li, Lin; Chen, Bin; Xu, Xiaofeng; Dai, Jianhui; Yang, Xiaojun; Zhang, Li; Cao, Guanghan; Xu, Zhu-an

    2014-10-22

    We investigated a series of nickel-based oxyarsenides LnNiAsO (Ln=La, Ce, Pr, Nd, Sm) compounds. CeNiAsO undergoes two successive anti-ferromagnetic transitions at TN1=9.3 K and TN2=7.3 K; SmNiAsO becomes an anti-ferromagnet below TN≃3.5 K; NdNiAsO keeps paramagnetic down to 2 K but orders anti-ferromagnetically below TN≃1.3 K. Superconductivity was observed only in Kramers non-magnetic LaNiAsO and PrNiAsO with Tc=2.7 K and 0.93 K, respectively. The superconductivity of PrNiAsO is further studied by upper critical field and specific heat measurements, which reveal that PrNiAsO is a weakly coupled Kramers non-magnetic superconductor. Our work confirms that the nickel-based oxyarsenide superconductors are substantially different in mechanism to iron-based ones, and are likely to be described by the conventional superconductivity theory.

  20. Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T

    CERN Document Server

    Larbalestier, D C; Trociewitz, U P; Kametani, F; Scheuerlein, C; Dalban-Canassy, M; Matras, M; Chen, P; Craig, N C; Lee, P J; Hellstrom, E E

    2014-01-01

    Magnets are the principal market for superconductors, but making attractive conductors out of the high-temperature cuprate superconductors (HTSs) has proved difficult because of the presence of high-angle grain boundaries that are generally believed to lower the critical current density, J$_c$. To minimize such grain boundary obstacles, HTS conductors such as REBa$_2$Cu$_3$O$_{7−x}$ and (Bi, Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10−x}$ are both made as tapes with a high aspect ratio and a large superconducting anisotropy. Here we report that Bi$_2$2Sr$_2$CaCu$_2$O$_{8−x}$ (Bi-2212) can be made in the much more desirable isotropic, round-wire, multifilament form that can be wound or cabled into arbitrary geometries and will be especially valuable for high-field NMR magnets beyond the present 1 GHz proton resonance limit of Nb$_3$Sn technology. An appealing attribute of this Bi-2212 conductor is that, being without macroscopic texture, it contains many high-angle grain boundaries but nevertheless attains a very hi...

  1. Oxypnictide SmFeAs(O,F) superconductor: a candidate for high-field magnet applications.

    Science.gov (United States)

    Iida, Kazumasa; Hänisch, Jens; Tarantini, Chiara; Kurth, Fritz; Jaroszynski, Jan; Ueda, Shinya; Naito, Michio; Ichinose, Ataru; Tsukada, Ichiro; Reich, Elke; Grinenko, Vadim; Schultz, Ludwig; Holzapfel, Bernhard

    2013-01-01

    The recently discovered oxypnictide superconductor SmFeAs(O,F) is the most attractive material among the Fe-based superconductors due to its highest transition temperature of 56 K and potential for high-field performance. In order to exploit this new material for superconducting applications, the knowledge and understanding of its electro-magnetic properties are needed. Recent success in fabricating epitaxial SmFeAs(O,F) thin films opens a great opportunity to explore their transport properties. Here we report on a high critical current density of over 10(5) A/cm(2) at 45 T and 4.2 K for both main field orientations, feature favourable for high-field magnet applications. Additionally, by investigating the pinning properties, we observed a dimensional crossover between the superconducting coherence length and the FeAs interlayer distance at 30-40 K, indicative of a possible intrinsic Josephson junction in SmFeAs(O,F) at low temperatures that can be employed in electronics applications such as a terahertz radiation source and a superconducting Qubit.

  2. Low-temperature transport measurements of superconductors and semiconductors in magnetic fields to 800 T

    Energy Technology Data Exchange (ETDEWEB)

    Dzurak, A.S.; Kane, B.E.; Clark, R.G.; Lumpkin, N.E.; O' Brien, J.; Facer, G.R.; Starrett, R.P.; Skougarevsky, A.; Nakagawa, H. [University of New South Wales, NSW (Australia). School of Physics, National Pulsed Magnet Laboratory and Semiconductor Nanofabrication Facility; Miura, N. [University of Tokyo, Tokyo (Japan). Institute for Solid State Physics; Rickel, D.G.; Goettee, J.D.; Campbell, L.J.; Fowler, C.M.; Mielke, C.; King, J.C.; Zerwekh, W.D.; Clark, D.; Bartram, B.D. [Los Alamos National Laboratory, Los Alamos, NM (United States); Ortenberg, M. von [Humboldt Universitaet, Berlin (Germany); Herlach, F. [Katholieke Universiteit Leuven, Leuven (Belgium); Yokoi, H. [National Research Institute for Metals, Tsukuba (Japan); Bykov, A.I.; Tatsenko, O.M.; Platonov, V.V. [All-Russian Research Institute of Experimental Physics (Russian Federation); Mitchell, E.E.; Hermann, J.; Mueller, K.-H. [Commonwealth Scientific and Industrial Research Organisation, NSW (Australia). Division of Telecommunications and Industrial Physics; Maranowski, K.D.; Gossard, A.C. [University of California, Santa Barbara, CA (United States)

    1998-07-01

    Recent innovations in sample lithography and measurement techniques have made possible electrical transport measurements on both high-T{sub c}. superconductor and semiconductor samples in the harsh environment of implosively generated magnetic fields B up to 800 T, with reliable data obtained up to 300 T. Thin films of the cuprate superconductor YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} have been studied with B directed parallel to the CuO planes (J parallel B perpendicular c-axis). At an ambient temperature of 1.6 K and a probe frequency of 0.9 GHz we find an onset of dissipation at B{sub on} (150 {+-} 20) T, the highest field yet reported. In addition, the measured upper critical field B{sub c2} = (240 {+-} 30) T is significantly above the paramagnetic limit for this material. Measurements on Al{sub x}Ga{sub 1-x}As/GaAs parabolic quantum well structures, designed to probe the existence of a magnetically induced triplet superconducting phase, and on HgSe: Fe samples are also discussed.

  3. A Magnetic Persistent Current Switch at milliKelvin Temperatures

    CERN Document Server

    van Waarde, Bob; Oosterkamp, Tjerk

    2016-01-01

    We report the development of a magnetically driven Persistent Current Switch operated in a dilution refrigerator. We show that it can be safely used to charge a 60 mH coil with 0.5 A at 11 mK, which heats up the dilution refrigerator to 60.5 mK. Measurements at 4 K on a 440 $\\mu$H coil reveal a residual resistance of $R \\leqslant 3.3$ p$\\Omega$.

  4. Measurement and calculation of levitation forces between magnets and granular superconductors

    Science.gov (United States)

    Johansen, T. H.; Bratsberg, H.; Baziljevich, M.; Hetland, P. O.; Riise, A. B.

    1995-01-01

    Recent developments indicate that exploitation of the phenomenon of magnetic levitation may become one of the most important near-term applications of high-T(sub c) superconductivity. Because of this, the interaction between a strong permanent magnet(PM) and bulk high-T(sub c) superconductor (HTSC) is currently a subject of much interest. We have studied central features of the mechanics of PM-HTSC systems of simple geometries. Here we report experimental results for the components of the levitation force, their associated stiffness and mechanical ac-loss. To analyze the observed behavior a theoretical framework based on critical-state considerations is developed. It will be shown that all the mechanical properties can be explained consistently at a quantitative level wing a minimum of model parameters.

  5. A pseudogap term in the magnetic response of the cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Walstedt, Professor Russell E. [University of Michigan; Mason, Dr. Thomas Edward [Oak Ridge National Laboratory (ORNL); Aeppli, Professor Gabriel [University College, London; Hayden, Professor Stephen M. [University of Bristol, UK; Mook Jr, Herbert A [ORNL

    2011-01-01

    We combine neutron scattering (INS) data and NMR/NQR nuclear spin lattice relaxation rate (1/T1) data to deduce the existence of a new contribution to the magnetic response (~q, ) in cuprate superconductors. This contribution, which has yet to be observed with INS, is shown to embody the magnetic pseudogap effects. As such, it explains the long-standing puzzle of pseudogap effects missing from cuprate INS data, dominated by stripe fluctuations, for (~q, ) at low energies. For La1.86Sr0.14CuO4 and Y Ba2Cu3O6.5, the new term is the chief contributor to 1/T1 for T Tc.

  6. A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors.

    Science.gov (United States)

    Egan, R; Philippe, M; Wera, L; Fagnard, J F; Vanderheyden, B; Dennis, A; Shi, Y; Cardwell, D A; Vanderbemden, P

    2015-02-01

    We report the design and construction of a flux extraction device to measure the DC magnetic moment of large samples (i.e., several cm(3)) at cryogenic temperature. The signal is constructed by integrating the electromotive force generated by two coils wound in series-opposition that move around the sample. We show that an octupole expansion of the magnetic vector potential can be used conveniently to treat near-field effects for this geometrical configuration. The resulting expansion is tested for the case of a large, permanently magnetized, type-II superconducting sample. The dimensions of the sensing coils are determined in such a way that the measurement is influenced by the dipole magnetic moment of the sample and not by moments of higher order, within user-determined upper bounds. The device, which is able to measure magnetic moments in excess of 1 A m(2) (1000 emu), is validated by (i) a direct calibration experiment using a small coil driven by a known current and (ii) by comparison with the results of numerical calculations obtained previously using a flux measurement technique. The sensitivity of the device is demonstrated by the measurement of flux-creep relaxation of the magnetization in a large bulk superconductor sample at liquid nitrogen temperature (77 K).

  7. Magnetic and orbital ordering in the iron-based superconductors. Role of spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Felix; Eremin, Ilya [Institut fuer Theoretische Physik III, Ruhr-Universitaet Bochum (Germany); Knolle, Johannes [Max Planck Institute for the Physics of Complex Systems, Dresden (Germany); Fernandes, Rafael [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN (United States)

    2015-07-01

    We analyze the magnetic ordering in the iron-based superconductors in presence of spin-orbit coupling. Based on several tight-binding parametrizations of the 3d electron states we show how the spin-orbit coupling introduces the anisotropy of the magnetization of the striped antiferromagnetic state by lifting the degeneracy of all three components of the magnetization m{sub x}, m{sub y} and m{sub z}. The orientation of the magnetic moment is determined by the contribution of the xy, xz, and yz orbitals to the electronic states near the Fermi level of the electron and hole bands and is determined by the electron filling. We find that within an itinerant approach the magnetic ordering is most favorable along the wavevector of the striped AF state. This appears to be a natural consequence of the spin-orbit coupling in the striped AF state where the ferro-orbital order of the xz and yz orbitals is only a consequence of the striped AF order. We further analyze the role of spin-orbit coupling for the C{sub 4} magnetic structure where SDW order parameters with both wavevectors, Q{sub x} = (π,0) and Q{sub y} = (0,π), coexist.

  8. Dependence of levitation force on frequency of an oscillating magnetic levitation field in a bulk YBCO superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Carter, Hamilton, E-mail: hcarter3@nmsu.edu [Department of Physics, New Mexico State University, Las Cruces, NM 88003 (United States); Pate, Stephen, E-mail: pate@nmsu.edu [Department of Physics, New Mexico State University, Las Cruces, NM 88003 (United States); Goedecke, George, E-mail: ggoedeck@nmsu.edu [Department of Physics, New Mexico State University, Las Cruces, NM 88003 (United States)

    2013-02-14

    Highlights: ► AC magnetic field strength required for levitation is independent of frequency. ► RMS magnetic field strength is in good agreement with DC magnetic field strength. ► Dependence of YBCO levitation force on AC magnetic field frequency is investigated. -- Abstract: The dependence of the magnetic field strength required for levitation of a melt textured, single domain YBCO superconductor disk on the frequency of the current generating the levitating magnetic field has been investigated. The magnetic field strength is found to be independent of frequency between 10 and 300 Hz. This required field strength is found to be in good experimental and theoretical agreement with the field strength required to levitate the same superconductor with a non-oscillating magnetic field. Hysteretic losses within the superconductor predicted by Bean’s critical-state model were also calculated. The measured data rules out any significant Bean’s model effects on the required levitation field strength within the measured frequency range.

  9. Magnetic property of iron-based superconductors%铁基超导体的磁性研究

    Institute of Scientific and Technical Information of China (English)

    王少雷; 张莉

    2012-01-01

    The brief history and applications of superconductivity was introduced. The structure of iron-based superconductors and magnetic materials were classified. Taking BaFe2As2 for example, the research on the coexistence of superconductivity and magnetism were summarized. In the meantime the abundant magnetic properties of iron-based superconductors such as SmOCoAs was discussed to show the importance of magnetic property of iron-based superconductors. Finally, viewpoints on the research of the mechanism of high Tc superconductivity and the discovery of new superconductors are presented.%介绍了超导电性的发展简史及其广阔用途,介绍了铁基超导体的结构分类和物质的磁性分类;以BaFe2As2为例综述了铁基超导体中铁磁和超导共存的研究现状,同时以SmOCoAs为例研究了1111相中丰富的磁结构,从而阐明磁性在铁基超导电性研究中的重要地位;最后针对高温超导微观机理研究和超导新材料探索提出了见解.

  10. Magnetic Flux Lines in Complex Geometry Type-II Superconductors Studied by the Time Dependent Ginzburg-Landau Equation

    DEFF Research Database (Denmark)

    Alstrøm, Tommy Sonne; Sørensen, Mads Peter; Pedersen, Niels Falsig

    2010-01-01

    The time-dependent Ginzburg-Landau equation is solved numerically for type-II superconductors of complex geometry using the finite element method. The geometry has a marked influence on the magnetic vortex distribution and the vortex dynamics. We have observed generation of giant vortices...

  11. LETTER TO THE EDITOR: Model of the mixed state of type-II superconductors in high magnetic fields

    Science.gov (United States)

    Landau, I. L.; Ott, H. R.

    2002-04-01

    In superconductors with large values of the Ginzburg-Landau parameter κ, exposed to magnetic fields close to the upper critical field Hc2, the magnetic field is practically homogeneous across the sample and the density of supercurrents is negligibly small. In this case, there is no obvious reason for the formation of Abrikosov vortices, characteristic for the well known mixed state. We consider an alternative model for describing the mixed state for κ>>1 and magnetic fields close to Hc2. We argue that with decreasing magnetic field the traditional vortex structure is adopted via a first-order phase transition, revealed by discontinuities in the magnetization as well as the resistivity.

  12. An active homopolar magnetic bearing with high temperature superconductor (HTS) coils and ferromagnetic cores

    Science.gov (United States)

    Brown, G. V.; Dirusso, E.; Provenza, A. J.

    1995-01-01

    A proof-of-feasibility demonstration showed that high temperature superconductor (HTS) coils can be used in a high-load, active magnetic bearing in liquid nitrogen. A homopolar radial bearing with commercially wound HTS (Bi 2223) bias and control coils produced over 200 lb (890 N) radial load capacity (measured non-rotating) and supported a shaft to 14000 rpm. The goal was to show that HTS coils can operate stably with ferromagnetic cores in a feedback controlled system at a current density similar to that in Cu in liquid nitrogen. Design compromises permitted use of circular coils with rectangular cross section. Conductor improvements will eventually permit coil shape optimization, higher current density and higher bearing load capacity. The bias coil, wound with non-twisted, multifilament HTS conductor, required negligible power to carry its direct current. The control coils were wound with monofilament HTS sheathed in Ag. These dissipated negligible power for direct current (i.e. for steady radial load components). When an alternating current (AC) was added, the AC component dissipated power which increased rapidly with frequency and quadratically with AC amplitude. In fact at frequencies above about 2 hz, the effective resistance of the control coil conductor actually exceeds that of the silver which is in electrical parallel with the oxide superconductor. This is at least qualitatively understandable in the context of a Bean-type model of flux and current penetration into a Type II superconductor. Fortunately the dynamic currents required for bearing stability are of small amplitude. These results show that while twisted multifilament conductor is not needed for stable levitation, twisted multifilaments will be required to reduce control power for sizable dynamic loads, such as those due to unbalance.

  13. Nanoscale magnetization of a single vortex in d-wave superconductors

    Science.gov (United States)

    Zakharchuk, I.; Januzaj, A.; Safonchik, M.; Traito, K. B.; Lähderanta, E.

    2017-01-01

    A finite-size scaling of the nanoscale magnetization m on size averaging R of a single vortex in d-wave bulk superconductor is developed using quasiclassical Eilenberger equations. Nanoscaling is anchoring around the linear London approximation for bulk superconductors. Comparing the results with those obtained in local nonlinear approach demonstrated the importance of the nonlocal contribution. Temperature dependences of two-point correlation function χ(T , R 1 , R 2) = m(T , R 2) / m(0 , R 2) - m(T , R 1) / m(0 , R 1) with R2 > R1 and one-point function χ(T, R1 → ∞, R2) are calculated. It is found that χ(T, R1, R2), R2 > R1, is a nonmonotonous function of temperature and changes sign at high temperatures. This nonmonotonous temperature dependence can be understood as a result of competition between various effects i) Volovik effect and nonlocal corrections to superconducting electron density dominating in low temperature range, and ii) current-induced suppression of the order parameter dominating at high temperatures. The introduced nonmagnetic disorder greatly suppresses the low temperature nonlocal and nonlinear effects, leaving the order parameter effects to prevail in the whole temperature range. Nonlocal pairing and tunneling effects are investigated at the superconductor - normal metal border by considering a d-wave superconducting dot (d-dot) inside a normal diffusive metal. These effects result in a suppression of the supercurrent in the vortex core and are essential in nanodots with relatively small sizes. At sizes larger than a temperature dependent characteristic length the nanoscale physics transforms into bulk solution.

  14. Influence of lateral displacement on the levitation performance of a magnetized bulk high-T{sub c} superconductor magnet

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W., E-mail: tonny-violet@163.com [College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu 610059 (China) and Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu 610031 (China); Wang, J.S.; Ma, G.T.; Zheng, J. [Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu 610031 (China); State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031 (China); National Laboratory of Rail Transit, Chengdu, 610031 (China); Tuo, X.G.; Li, L.L. [College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu 610059 (China); Ye, C.Q.; Liao, X.L. [Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu 610031 (China); National Laboratory of Rail Transit, Chengdu, 610031 (China); Wang, S.Y. [Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu 610031 (China); State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031 (China); National Laboratory of Rail Transit, Chengdu, 610031 (China)

    2012-03-15

    Compared with the permanent magnet, the magnetized bulk high-T{sub c} superconductor magnet (MBSCM) can trap higher magnetic field due to its strong flux pinning ability, so it is a good candidate to improve the levitation performance of high-T{sub c} superconductive (HTS) maglev system. The trapped magnetic flux of a MBSCM is sustained by the inductive superconducting current produced by the magnetizing process and is susceptible to the current intensity as well as configuration. In the HTS maglev system, the lateral displacement is an important process to change the superconducting current within a MBSCM and then affects its levitation performance, which is essential for the traffic ability in curve-way, the loading capacity of lateral impact and so on. The research about influence of lateral displacement on the levitation performance of MBSCM is necessary when MBSCM is applied on the HTS maglev vehicle. The experimental investigations about the influence of lateral displacement on the levitation performance of a MBSCM with different trapped fluxes and applied fields are processed in this article. The analyses and conclusions of this article are useful for the practical application of MBSCM in HTS maglev system.

  15. Interaction of bulk superconductors with flywheel rings made of multiple permanent magnets

    Science.gov (United States)

    Ikeda, M.; Wongsatanawarid, A.; Seki, H.; Murakami, M.

    2009-10-01

    Compared to conventional mechanical bearings, superconducting bearings have the advantage that there is no friction loss. Thus the superconducting bearings are employed for a flywheel energy storage device, and thereby one can construct the system that stores the energy for a long duration. Hence, superconducting flywheel energy storage system has attracted worldwide attention. For practical applications of the superconducting energy storage system, the stored energy must be maximized that can be achieved by either increasing the diameter of the levitated flywheel or the rotational velocity. Since the suspended flywheel in the superconducting flywheel energy storage system is made of permanent magnets, its size is limited by the size of permanent magnets. In addition, when the rotational speed is increased, there is possibility for the magnet ring to fracture due to a large centrifugal force. We therefore proposed the construction of the magnetic flywheel ring by simply arranging small permanent magnets pasted into machined grooves in Al disk 650 mm in diameter. Then we measured the force interaction between superconductor sample and a invented flywheel design. We have found that the field is almost uniform when the distance from the flywheel surface exceeded 15 mm, showing that frictionless rotation is possible at the gap larger than 15 mm. Furthermore, the repulsive force density was 0.48 N/cm 2 at 15 mm, which demonstrates that the mass of 161.32 kg can be levitated.

  16. Magnetic properties of high-T(sub c) superconductors: Rigid levitation, flux pinning, thermal depinning, and fluctuation

    Science.gov (United States)

    Brandt, E. H.

    1990-01-01

    The levitation of high-T(sub c) superconductors is quite conspicuous: Above magnets of low symmetry a disk of these ceramics floats motionless, without vibration or rotation; it has a continuous range of stable positions and orientations as if it were stuck in sand. Some specimens may even be suspended above or below the same magnet. This fascinating stability, inherent to no other type of levitation, is caused by the pinning of magnetic flux lines by inhomogeneities inside these extreme type-2 superconductors. The talk deals with pinning of magnetic flux in these materials, with flux flow, flux creep, thermally activated depinning, and the thermal fluctuation of the vortex positions in the flux line lattice (often called flux lattice melting). Also discussed are the fluctuations of the (nearly periodic) magnetic field inside these superconductors which are caused by random pinning sites and by the finite temperature. These fluctuations broaden the van-Hove singularities observed in the density of the magnetic field by nuclear magnetic resonance and by muon spin rotation.

  17. Nanoscale probe of magnetism, orbital occupation, and structural distortions in iron-based superconductors

    Science.gov (United States)

    Cantoni, Claudia

    2014-03-01

    Local probes of atomic and electronic structures with sub-nanometer spatial resolution can provide additional insights into the physics of iron-based superconductors (FBS) by resolving the influence of inhomogeneities that are typically averaged over by bulk-sensitive techniques. Here we apply aberration-corrected scanning transmission electron microscopy coupled with electron energy loss spectroscopy to a wide class of iron-based superconductors and parent compounds to decipher the interplay between crystal distortions, local magnetic moment, orbital occupancy, and charge doping in these complex materials. In addition to revealing universal trends for hole concentration and local magnetic moment across families of FBS, we directly observe the effects of magneto-elastic coupling in 122 arsenides at room temperature, well above the structural and antiferromagnetic transition. The presence of atomic displacements indicates that the C4 tetragonal symmetry is already broken at room temperature in unstrained crystals, lowering the symmetry to orthorhombic (I2mm), and that all of the crystals are twinned with domains the size of a few nanometers. By tracking these local atomic displacements as a function of doping level x, in Ba(Fe1-xCox)2 As2, we find that the domain size correlates with the magnitude of the dynamic Fe moment, and both are enhanced near optimal doping where the ordered moment is suppressed. The non-monotonic behavior of the local Fe magnetic moment is linked to the strong coupling between lattice, spin, and orbital degrees of freedom. Research supported by the Materials Sciences and Engineering Division Office of Basic Energy Sciences, U.S. Department of Energy.

  18. Hysteresis force loss and damping properties in a practical magnet-superconductor maglev test vehicle

    Energy Technology Data Exchange (ETDEWEB)

    Yang Wenjiang; Liu Yu; Wen Zheng; Chen Xiaodong; Duan Yi [School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)

    2008-01-15

    In order to investigate the feasible application of a permanent magnet-high-temperature superconductor (PM-HTS) interaction maglev system to a maglev train or a space vehicle launcher, we have constructed a demonstration maglev test vehicle. The force dissipation and damping of the maglev vehicle against external disturbances are studied in a wide range of amplitudes and frequencies by using a sine vibration testing set-up. The dynamic levitation force shows a typical hysteresis behavior, and the force loss is regarded as the hysteresis loss, which is believed to be due to flux motions in superconductors. In this study, we find that the hysteresis loss has weak frequency dependence at small amplitudes and that the dependence increases as the amplitude grows. To analyze the damping properties of the maglev vehicle at different field cooling (FC) conditions, we also employ a transient vibration testing technique. The maglev vehicle shows a very weak damping behavior, and the damping is almost unaffected by the trapped flux of the HTSs in different FC conditions, which is believed to be attributed to the strong pinning in melt-textured HTSs.

  19. Hysteresis force loss and damping properties in a practical magnet superconductor maglev test vehicle

    Science.gov (United States)

    Yang, Wenjiang; Liu, Yu; Wen, Zheng; Chen, Xiaodong; Duan, Yi

    2008-01-01

    In order to investigate the feasible application of a permanent magnet-high-temperature superconductor (PM-HTS) interaction maglev system to a maglev train or a space vehicle launcher, we have constructed a demonstration maglev test vehicle. The force dissipation and damping of the maglev vehicle against external disturbances are studied in a wide range of amplitudes and frequencies by using a sine vibration testing set-up. The dynamic levitation force shows a typical hysteresis behavior, and the force loss is regarded as the hysteresis loss, which is believed to be due to flux motions in superconductors. In this study, we find that the hysteresis loss has weak frequency dependence at small amplitudes and that the dependence increases as the amplitude grows. To analyze the damping properties of the maglev vehicle at different field cooling (FC) conditions, we also employ a transient vibration testing technique. The maglev vehicle shows a very weak damping behavior, and the damping is almost unaffected by the trapped flux of the HTSs in different FC conditions, which is believed to be attributed to the strong pinning in melt-textured HTSs.

  20. Topological superconductivity and Majorana fermions in chains of magnetic atoms on the surface of a superconductor

    Science.gov (United States)

    Yazdani, Ali

    2015-03-01

    Chain of magnetic atoms on the surface of a BCS superconductor is a versatile platform for the realization of one-dimensional superconductors with Majorana bound states that lends itself to high-resolution scanning tunneling microscopy studies. In this talk, I will describe experimental efforts to realize this platform using self-assembled chains of Fe atoms on the surface of Pb (110) and to directly visualize Majorana quasi-particle bound states at their edges. Using spin-polarized STM studies, we show that Fe chains are ferromagnetic while tunneling into Pb's substrate demonstrates signatures of strong spin-orbit interaction at its surface. Comparison of experimental measurements of structure and normal state electronic structure with DFT calculations suggest that these are triple zigzag chains with an odd number of band-crossings at the Fermi level. The onset of superconductivity in the Pb strongly modifies the low energy density of states of the Fe chains and induces a zero energy state at their ends. I will describe how these observations are consistent with the formation of a topological superconducting phase with Majorana edge states. Work supported by ONR, NSF-DMR, NSF-MRSEC, ARO-MURI, and LPS-ARO grants.

  1. Unconventional superconductors under a rotating magnetic field. I. Density of states and specific heat

    Science.gov (United States)

    Vorontsov, A. B.; Vekhter, I.

    2007-06-01

    We develop a fully microscopic theory for the calculations of the angle-dependent properties of unconventional superconductors under a rotated magnetic field. We employ the quasiclassical Eilenberger equations and use a variation of the Brandt-Pesch-Tewordt (BPT) method to obtain a closed-form solution for the Green’s function. The equations are solved self-consistently for quasi-two-dimensional dx2-y2(dxy) superconductors with the field rotated in the basal plane. The solution is used to determine the density of states and the specific heat. We find that applying the field along the gap nodes may result in minima or maxima in the angle-dependent specific heat, depending on the location in the T-H plane. This variation is attributed to the scattering of the quasiparticles on vortices, which depends on both the field and the quasiparticle energy, and is beyond the reach of the semiclassical approximation. We investigate the anisotropy across the T-H phase diagram and compare our results with the experiments on heavy fermion CeCoIn5 .

  2. Gap-related trapped magnetic flux dependence between single and combined bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Z., E-mail: zgdeng@gmail.co [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, Tokyo 135-8533 (Japan); Miki, M.; Felder, B.; Tsuzuki, K.; Shinohara, N.; Uetake, T.; Izumi, M. [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, Tokyo 135-8533 (Japan)

    2011-05-15

    Highlights: {yields} Rectangular YBCO bulks to realize a compact combination. {yields} The gap effect was added to consider in the trapped flux density mapping. {yields} The trapped-flux dependence between single and combined bulks is gap related. {yields} It is possible to estimate the total magnetic flux of bulk combinations. - Abstract: Aiming at examining the trapped-flux dependence between single and combined bulk superconductors for field-pole applications, three rectangular Y{sub 1.65}Ba{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) bulks with a possibly compact combination were employed to investigate the trapped-flux characteristics of single and combined bulks with a field-cooling magnetization (FCM) method. A gap-related dependence was found between them. At lower gaps of 1 mm and 5 mm, the peak trapped fields and total magnetic flux of combined bulks are both smaller than the additive values of each single bulk, which can be ascribed to the demagnetization influences of the field around the bulk generated by the adjacent ones. While, at larger gaps like 10 mm, the situation becomes reversed. The combined bulks can attain bigger peak trapped fields as well as total magnetic flux, which indicates that the magnetic field by the bulk combination can reach higher gaps, thanks to the bigger magnetic energy compared with the single bulk. The presented results show that, on one hand, it is possible to estimate the total trapped magnetic flux of combined bulks by an approximate additive method of each single bulk while considering a demagnetization factor; on the other hand, it also means that the performance of combined bulks will be superior to the addition of each single bulk at larger gaps, thus preferable for large-scaled magnet applications.

  3. Magnetism, Superconductivity, and Spontaneous Orbital Order in Iron-Based Superconductors: Which Comes First and Why?

    Directory of Open Access Journals (Sweden)

    Andrey V. Chubukov

    2016-12-01

    Full Text Available Magnetism and nematic order are the two nonsuperconducting orders observed in iron-based superconductors. To elucidate the interplay between them and ultimately unveil the pairing mechanism, several models have been investigated. In models with quenched orbital degrees of freedom, magnetic fluctuations promote stripe magnetism, which induces orbital order. In models with quenched spin degrees of freedom, charge fluctuations promote spontaneous orbital order, which induces stripe magnetism. Here, we develop an unbiased approach, in which we treat magnetic and orbital fluctuations on equal footing. Key to our approach is the inclusion of the orbital character of the low-energy electronic states into renormalization group (RG analysis. We analyze the RG flow of the couplings and argue that the same magnetic fluctuations, which are known to promote s^{+-} superconductivity, also promote an attraction in the orbital channel, even if the bare orbital interaction is repulsive. We next analyze the RG flow of the susceptibilities and show that, if all Fermi pockets are small, the system first develops a spontaneous orbital order, then s^{+-} superconductivity, and magnetic order does not develop down to T=0. We argue that this scenario applies to FeSe. In systems with larger pockets, such as BaFe_{2}As_{2} and LaFeAsO, we find that the leading instability is either towards a spin-density wave or superconductivity. We argue that in this situation nematic order is caused by composite spin fluctuations and is vestigial to stripe magnetism. Our results provide a unifying description of different iron-based materials.

  4. Magnetism, Superconductivity, and Spontaneous Orbital Order in Iron-Based Superconductors: Which Comes First and Why?

    Science.gov (United States)

    Chubukov, Andrey V.; Khodas, M.; Fernandes, Rafael M.

    2016-10-01

    Magnetism and nematic order are the two nonsuperconducting orders observed in iron-based superconductors. To elucidate the interplay between them and ultimately unveil the pairing mechanism, several models have been investigated. In models with quenched orbital degrees of freedom, magnetic fluctuations promote stripe magnetism, which induces orbital order. In models with quenched spin degrees of freedom, charge fluctuations promote spontaneous orbital order, which induces stripe magnetism. Here, we develop an unbiased approach, in which we treat magnetic and orbital fluctuations on equal footing. Key to our approach is the inclusion of the orbital character of the low-energy electronic states into renormalization group (RG) analysis. We analyze the RG flow of the couplings and argue that the same magnetic fluctuations, which are known to promote s+- superconductivity, also promote an attraction in the orbital channel, even if the bare orbital interaction is repulsive. We next analyze the RG flow of the susceptibilities and show that, if all Fermi pockets are small, the system first develops a spontaneous orbital order, then s+- superconductivity, and magnetic order does not develop down to T =0 . We argue that this scenario applies to FeSe. In systems with larger pockets, such as BaFe2 As2 and LaFeAsO, we find that the leading instability is either towards a spin-density wave or superconductivity. We argue that in this situation nematic order is caused by composite spin fluctuations and is vestigial to stripe magnetism. Our results provide a unifying description of different iron-based materials.

  5. Modelling and comparison of trapped fields in (RE)BCO bulk superconductors for activation using pulsed field magnetization

    Science.gov (United States)

    Ainslie, M. D.; Fujishiro, H.; Ujiie, T.; Zou, J.; Dennis, A. R.; Shi, Y.-H.; Cardwell, D. A.

    2014-06-01

    The ability to generate a permanent, stable magnetic field unsupported by an electromotive force is fundamental to a variety of engineering applications. Bulk high temperature superconducting (HTS) materials can trap magnetic fields of magnitude over ten times higher than the maximum field produced by conventional magnets, which is limited practically to rather less than 2 T. In this paper, two large c-axis oriented, single-grain YBCO and GdBCO bulk superconductors are magnetized by the pulsed field magnetization (PFM) technique at temperatures of 40 and 65 K and the characteristics of the resulting trapped field profile are investigated with a view of magnetizing such samples as trapped field magnets (TFMs) in situ inside a trapped flux-type superconducting electric machine. A comparison is made between the temperatures at which the pulsed magnetic field is applied and the results have strong implications for the optimum operating temperature for TFMs in trapped flux-type superconducting electric machines. The effects of inhomogeneities, which occur during the growth process of single-grain bulk superconductors, on the trapped field and maximum temperature rise in the sample are modelled numerically using a 3D finite-element model based on the H-formulation and implemented in Comsol Multiphysics 4.3a. The results agree qualitatively with the observed experimental results, in that inhomogeneities act to distort the trapped field profile and reduce the magnitude of the trapped field due to localized heating within the sample and preferential movement and pinning of flux lines around the growth section regions (GSRs) and growth sector boundaries (GSBs), respectively. The modelling framework will allow further investigation of various inhomogeneities that arise during the processing of (RE)BCO bulk superconductors, including inhomogeneous Jc distributions and the presence of current-limiting grain boundaries and cracks, and it can be used to assist optimization of

  6. Magnetization measurements on the Reentrant Superconductor ERxY1-xRh1.1Sn3.6

    NARCIS (Netherlands)

    Blank, D.H.A.; Flokstra, J.

    1987-01-01

    We performed magnetization measurements on the reentrant magnetic superconductor ErxY1-xRh1.1Sn3.6 (x = 0.8, 0.9, 1) using a SQUID magnetometer in a 3He-4 He dilution refrigerator. The temperature was varied between 50 mK and 2 K and different background fields were used. The experiments were concen

  7. Experimental Study on Current Decay Characteristics of Persistent Current HTS Magnet by Alternating Magnetic Field

    Science.gov (United States)

    Park, Young Gun; Lee, Chang Young; Hwang, Young Jin; Lee, Woo Seung; Lee, Jiho; Jo, Hyun Chul; Chung, Yoon Do; Ko, Tae Kuk

    This paper deals with a current decay characteristics of a high temperature superconducting (HTS) magnet operated in persistent current mode (PCM). In superconducting synchronous machine applications such as linear synchronous motor (LSM), the superconducting coil is designed to operate in the PCM to obtain steady magnetic field with DC transport current. This superconducting magnet operates on a direct current, but it can be exposed to alternating magnetic field due to the armature winding. When the magnet is subjected to an external time-varying magnetic field, it is possible to result in a decay of the current in PCM system due to AC loss. In this research, a PCM system with armature coil which generates time-varying magnetic field was fabricated to verify current decay characteristics by external alternating magnetic field. The current decay rate was measured by using a hall sensor as functions of amplitude and frequency of armature coil.

  8. Holographic Superconductors with Logarithmic Nonlinear Electrodynamics in an External Magnetic Field

    CERN Document Server

    Sheykhi, A

    2016-01-01

    Based on the matching method, we explore the effects of adding an external magnetic field on the $s$-wave holographic superconductor when the gauge field is in the form of the logarithmic nonlinear source. First, we obtain the critical temperature as well as the condensation operator in the presence of logarithmic nonlinear electrodynamics and understand that they depend on the nonlinear parameter $b$. We show that the critical temperature decreases with increasing $b$, which implies that the nonlinear gauge field makes the condensation harder. Then, we turn on the magnetic field in the bulk and find the critical magnetic field, $B_c$, in terms of the temperature, which also depends on the nonlinear parameter $b$. We observe that for temperature smaller than the critical temperature, $Tmagnetic field increases with increasing $b$ and goes to zero as $T\\rightarrow T_c$, independent of the nonlinear parameter $b$. In the limiting case where $ b\\rightarrow0 $, all results restore those of ...

  9. Magnetic flux disorder and superconductor-insulator transition in nanohole thin films

    Science.gov (United States)

    Granato, Enzo

    2016-08-01

    We study the superconductor-insulator transition in nanohole ultrathin films in a transverse magnetic field by numerical simulation of a Josephson-junction array model. Geometrical disorder due to the random location of nanoholes in the film corresponds to random flux in the array model. Monte Carlo simulation in the path-integral representation is used to determine the critical behavior and the universal resistivity at the transition as a function of disorder and average number of flux quanta per cell, fo. The resistivity increases with disorder for noninteger fo while it decreases for integer fo, and reaches a common constant value in a vortex-glass regime above a critical value of the flux disorder Dfc. The estimate of Dfc and the resistivity increase for noninteger fo are consistent with recent experiments on ultrathin superconducting films with positional disordered nanoholes.

  10. Interference effect on pairing correlations in a metal-superconductor-metal layer with magnetic interfaces

    Science.gov (United States)

    Choi, Chi-Hoon

    2012-05-01

    We study the proximity effect in a multilayer composed of a normal metal and a superconductor with spin-active interfaces. The symmetry of the induced pair amplitude is analyzed while varying the interface distance and the direction of the interface spins. We apply the general Green's function formalism without making the quasiclassical approximation in order to study the interference effect from the surrounding interfaces of the superconducting layer. By utilizing the formalism developed by A. Millis et al., we compute the Keldysh Green's function while incorporating the general boundary condition for magnetic interfaces of a superconducting heterostructure. The interference can have a profound effect on the proximity phenomena in the ballistic limit when the interface distance becomes less than the superconducting coherence length. We also discuss the effect of the direction of the interface spins on the induction of the odd-frequency equal-spin pairing state, which is important for applications of ferromagnetic quantum devices.

  11. High-Tc Superconductor Detection Coils for a Magnetic Resonance System

    Institute of Scientific and Technical Information of China (English)

    康琳; 吴培亨; 潘俊; 蔡卫星; 杨森祖; 曹春海

    2002-01-01

    Considering that in a magnetic resonance system, if the detection coil contributes dominantly to the system noise, the performance of the whole system can certainly be improved by switching to a detection coil made of a high-temperature superconductor, and using YBa2Cu3O7 thinfilms on 25 × 25 mm2 LaAIO3 substrates, we have prepared two kinds of detection coils: single-coil and two-coil. Encouragingly, their quality factors are measured to be Q > 2500 for two-coil (at 22.566MHz and 77K) and Q > 5500 for single-coil (at 92.3MHz and 77K),respectively. Here, we describe the details of the design, fabrication and testing of the coils.

  12. Electronic structure, magnetic and superconducting properties of co-doped iron-arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Rosner, Helge; Schnelle, Walter; Nicklas, Michael; Leithe-Jasper, Andreas [MPI CPfS Dresden (Germany); Weikert, Franziska [Los Alamos National Laboratory, New Mexico (United States); HLD Dresden Rossendorf (Germany); Wosnitza, Joachim [HLD Dresden Rossendorf (Germany)

    2013-07-01

    We present a joint experimental and theoretical study of co-doped iron-arsenide superconductors of the 122 family A{sub 1-x}K{sub x}Fe{sub 2-y}T{sub y}As{sub 2} (A = Ba,Sr,Eu; T = Co,Ru,Rh). In these systems, the co-doping enables the separation of different parameters - like electron count, disorder or the specific geometry of the FeAs layer - with respect to the position of the respective compounds in the general 122 phase diagram. For a series of compounds, we investigate the relevance of the different parameters for the magnetic, thermodynamic and superconducting properties. Our experimental investigations are supported by density functional electronic structure calculations applying different approximations for doping and disorder.

  13. Magnetic Flux Compression Using Detonation Plasma Armatures and Superconductor Stators: Integrated Propulsion and Power Applications

    Science.gov (United States)

    Litchford, Ron; Robertson, Tony; Hawk, Clark; Turner, Matt; Koelfgen, Syri

    1999-01-01

    This presentation discusses the use of magnetic flux compression for space flight applications as a propulsion and other power applications. The qualities of this technology that make it suitable for spaceflight propulsion and power, are that it has high power density, it can give multimegawatt energy bursts, and terawatt power bursts, it can produce the pulse power for low impedance dense plasma devices (e.g., pulse fusion drivers), and it can produce direct thrust. The issues of a metal vs plasma armature are discussed, and the requirements for high energy output, and fast pulse rise time requires a high speed armature. The plasma armature enables repetitive firing capabilities. The issues concerning the high temperature superconductor stator are also discussed. The concept of the radial mode pulse power generator is described. The proposed research strategy combines the use of computational modeling (i.e., magnetohydrodynamic computations, and finite element modeling) and laboratory experiments to create a demonstration device.

  14. Compensation of the Persistent Current Multipoles in the LHC Dipoles by making the Coil Protection Sheet from Soft Magnetic Material

    CERN Document Server

    Völlinger, C

    2000-01-01

    This note presents a scheme for compensating the persistent current multipole errors of the LHC dipoles by making the coil protection sheets from soft magnetic material of 0.5 mm thickness. The material properties assumed in this study are those of iron sheets with a very low content of impurities (99.99% pure Fe). The non-linearities in the upramp cycle on the b3 multipole component can be reduced by the factor of four (while decreasing the b5 variation by the factor of two. Using sheets of slightly different thicknesses offers a tuning possibility for the series magnet coils and can compensate deviations arising from cables of different suppliers. The calculation method is based on a semi-analytical hysteresis model for hard superconductors and an M(B) - iteration using the method of coupled boundary elements - finite elements (BEM - FEM). It is now possible to compute persistent current multipole errors of geometries with arbitrarily shaped iron yokes and thin layers of soft magnetic material such as tunin...

  15. Improving magnetic properties of MgB{sub 2} bulk superconductors by synthetic engine oil treatment

    Energy Technology Data Exchange (ETDEWEB)

    Taylan Koparan, E., E-mail: etaylan20@gmail.com [Department of Science Education, Eregli Faculty of Education, Bulent Ecevit University, TR-67300, Zonguldak (Turkey); Savaskan, B. [Energy Systems Engineering, Faculty of Technology, Karadeniz Technical University, 61830, Of, Trabzon (Turkey); Yanmaz, E. [Department of Mechatronics, Faculty of Engineering and Architecture, İstanbul Gelişim University, İstanbul (Turkey)

    2016-08-15

    Highlights: • The effects of synthetic engine oil treatment on magnetic properties of bulk MgB{sub 2} superconductors has been first time investigated and reported. • Synthetic engine oil used as a product which is cheap and a rich carbon source obviously has improved the superconducting magnetic properties of MgB{sub 2}. • The critical current density of all of MgB{sub 2} samples immersed at different standby time in engine oil in whole field range has been better than that of the pure MgB{sub 2} sample. • The MgB{sub 2} sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. - Abstract: The present study focuses on the effects of standby time of the MgB{sub 2} samples immersed in synthetic engine oil on the critical current density ( J{sub c}(H)), magnetic field dependence of the pinning force density f{sub p}(b) and T{sub c} performances of MgB{sub 2} bulk superconductors. Synthetic engine oil was used as a product which is cheap and a rich carbon source. Manufactured MgB{sub 2} pellet samples were immersed at different standby time of 30 min, 120 min, 300 min and 1440 min in synthetic engine oil after the first heating process. Finally, MgB{sub 2} samples immersed in synthetic engine oil were sintered at 1000 °C and kept for 15 min in Ar atmosphere. The critical current density of all of MgB{sub 2} samples immersed at different standby time in engine oil in whole field range was better than that of the pure MgB{sub 2} sample because of the number of the pinning centers. The MgB{sub 2} sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. The J{sub c} value for the pure sample is 2.0 × 10{sup 3} A/cm{sup 2}, whereas for the MgB{sub 2} sample immersed at 300 min standby time in engine oil the J{sub c} is enhanced to 4.8 × 10{sup 3} A/cm{sup 2} at 5 K and 3 T. The superconducting transition temperature (T{sub c}) did not change

  16. Superconducting magnetic control system for manipulation of particulate matter and magnetic probes in medical and industrial applications

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Yung Sheng; Hull, John R.; Askew, Thomas R.

    2006-07-11

    A system and method of controlling movement of magnetic material with at least first and second high temperature superconductors at spaced locations. A plurality of solenoids are associated with the superconductors to induce a persistent currents in preselected high temperature superconductors establishing a plurality of magnetic fields in response to pulsed currents introduced to one or more of the solenoids. Control mechanism in communication with said solenoids and/or said high temperature superconductors are used to demagnetize selected ones of the high temperature superconductors to reduce the magnetic fields substantially to zero. Magnetic material is moved between magnetic fields by establishing the presence thereof and thereafter reducing magnetic fields substantially to zero and establishing magnetic fields in other superconductors arranged in a predetermined configuration.

  17. Magnetic properties of the hydrogenated unconventional superconductor UCoGe-H

    Energy Technology Data Exchange (ETDEWEB)

    Adamska, Anna [Charles Univ., Dept. of Condensed Matter Physics, Prague (Czech Republic); AGH Univ. of Science and Technology, Dept. of Condensed Matter Physics, Cracow (Poland); Havela, Ladislav; Eichinger, Karl; Pospisil, Jiri [Charles Univ., Dept. of Condensed Matter Physics, Prague (Czech Republic); Miliyanchuk, Khrystyna [Ivan Franko National Univ. of Lviv (Ukraine). Dept. of Inorganic Chemistry

    2009-09-15

    The effect of hydrogenation on magnetic properties of the weakly ferromagnetic superconductor UCoGe was studied. UCoGe hydrides were synthesized at T = 773 K at different pressure of H{sub 2} gas (8, 5, 2 bar). The hydrogenation at 8 bar and 5 bar results in a change of the crystal structure from orthorhombic (TiNiSi structure type) to hexagonal (ZrBeSi type) with H concentrations just below 2 H/f.u. For one of such {beta}-hydrides, UCoGeH{sub 1.7}, the Curie temperature increases from 3 K up to 50 K and the spontaneous magnetic moment from 0.03 {mu}{sub B}/f.u. to 0.05 {mu}{sub B}/f.u. An {alpha}-hydride of UCoGe ({delta}V/V = 0.25%) with a hydrogen concentration 0.1 H/f.u. was obtained at 2 bar. It has the same crystal structure as a pure compound and surprisingly exhibits no magnetic order. (orig.)

  18. Superconductors with low critical temperature for electro-magnets; Supraconducteurs a basse temperature critique pour electroaimants

    Energy Technology Data Exchange (ETDEWEB)

    Devred, A

    2002-07-01

    Among the superconductors with low critical temperature that are used to build magnets, NbTi has reached a development state that allows a massive production for big equipment of physics and an industrial production in the domain of medicine imaging. The material that might challenge the supremacy of NbTi is Nb{sub 3}Sn but some technical difficulties have yet to be overcome. This report begins with a review of the different industrial processes used to produce superconducting wires based on the NbTi and Nb{sub 3}Sn materials. The transition from the superconducting state to the resistive normal state is described for both materials, the magnetizing of multi-wire superconducting cables is also presented. The author details the different patterns of wires in cables and proposes a formulary that allows the determination, in some simple cases,of energy losses that are generated in a superconducting cable by a variable magnetic field. (A.C.)

  19. Nature of the superconductor-insulator transition in disordered superconductors.

    Science.gov (United States)

    Dubi, Yonatan; Meir, Yigal; Avishai, Yshai

    2007-10-18

    The interplay of superconductivity and disorder has intrigued scientists for several decades. Disorder is expected to enhance the electrical resistance of a system, whereas superconductivity is associated with a zero-resistance state. Although superconductivity has been predicted to persist even in the presence of disorder, experiments performed on thin films have demonstrated a transition from a superconducting to an insulating state with increasing disorder or magnetic field. The nature of this transition is still under debate, and the subject has become even more relevant with the realization that high-transition-temperature (high-T(c)) superconductors are intrinsically disordered. Here we present numerical simulations of the superconductor-insulator transition in two-dimensional disordered superconductors, starting from a microscopic description that includes thermal phase fluctuations. We demonstrate explicitly that disorder leads to the formation of islands where the superconducting order is high. For weak disorder, or high electron density, increasing the magnetic field results in the eventual vanishing of the amplitude of the superconducting order parameter, thereby forming an insulating state. On the other hand, at lower electron densities or higher disorder, increasing the magnetic field suppresses the correlations between the phases of the superconducting order parameter in different islands, giving rise to a different type of superconductor-insulator transition. One of the important predictions of this work is that in the regime of high disorder, there are still superconducting islands in the sample, even on the insulating side of the transition. This result, which is consistent with experiments, explains the recently observed huge magneto-resistance peak in disordered thin films and may be relevant to the observation of 'the pseudogap phenomenon' in underdoped high-T(c) superconductors.

  20. Electronic and magnetic properties of the ferromagnetic superconductor UCoGe

    Science.gov (United States)

    Antonov, V. N.

    2017-01-01

    The electronic structure and x-ray magnetic circular dichroism (XMCD) spectra of the ferromagnetic superconductor UCoGe at the U N4,5, Ge and Co K and Co L2,3 edges were investigated theoretically from first principles, using the fully relativistic Dirac linear muffin-tin orbital band structure method. The electronic structure is obtained with the local spin-density approximation (LSDA), as well as with a generalization of the LSDA+U method which takes into account the non-diagonal occupation matrix (in spin indexes) of localized electrons. A stable ferromagnetic ground state was found. The uranium total magnetic moment is quite small (about -0.171μB) in the LSDA approximation as a result of almost complete cancellation between the spin magnetic moment of 0.657 μB and the opposite orbital magnetic moment of -0.828 μB, resulting from strong spin-orbit coupling at the uranium site. Valency of U ion in UCoGe is close to 3+. The ratio orbital and spin magnetic moments Ml/Ms ranged from 1.163 in the GGA approach up to 2.456 for the LSDA+U calculations is smaller than the corresponding ratio for the free ion U3+ value (2.60), it can indicate a significant delocalization of the 5f-electron states due to the hybridization of the U 5f electrons with the conduction band and Co 3d electrons. The line shape of the dichroic spectra at the U M5 and M4 edges predicted by considering the magneto-optical selection rules as well as the occupation and the energy sequence of the mj-projected partial densities of states. The theoretically calculated XMCD spectra at the U M4,5, Ge and Co K and Co L2,3 edges are in good agreement with the experimentally measured spectra.

  1. MHD-, ships-, jet engine unit consisting of electrochemical cells producing hydrogen, magneto-caloric hydrogen liquefier, liquid hydrogen-cooled high temperature superconductor-, MHD-, jet engine, liquid hydrogen internal combustion engine as high temperature-, superconductor-, generator-drive. High temperature superconductor coil and permanent magnet superconductor hollow cylinder as battery. MHD-Schiffs-Strahltriebwerks-Aggregat bestehend aus Wasserstoff-produzierenden elektrochemischen Solarzellen, magnetokalorischem Wasserstoffverfluessiger, Fluessigwasserstoff gekuehltem Hochtemperatur-Supraleiter-MHD-Strahltriebwerk, Fluessigwasserstoff-Verbrennungsmotor als Hochtemperatur-Supraleiter-Generator-Antrieb, Hochtemperatur-Supraleiter-Spule und permanentmagnetischem Supraleiter-Hohlzylinder als Akku

    Energy Technology Data Exchange (ETDEWEB)

    Berling, E.

    1991-05-02

    MHD-, ships-, jet engine-unit consisting of electrochemical cells producing hydrogen, magneto-caloric hydrogen liquifier, liquid hydrogen-cooled high temperature superconductor-, MHD-, jet engine, liquid hydrogen internal combustion engine as high temperature-, superconductor-, generator-drive. High temperature superconductor coil and permanent magnet superconductor hollow cylinder as battery. Ships water jet engines with magneto hydrodynamic (MHD) low temperature superconductor drive are known. The invention of the ceramic high temperature superconductor MHD drive, which is cooled with liquid hydrogen. The hydrogen is obtained electro-chemically directly from seawater, and is liquified magneto-calorically. The high temperature superconductor elements of the engine, liquifier, generator, storage coil, permanent magnet hollow cylinder store are coupled by a common liquid hydrogen cooling circuit. The internal combustion engine driving the generator is fuelled by the same liquid hydrogen by which the high temperature superconductor elements are cooled.

  2. Improving magnetic properties of MgB2 bulk superconductors by synthetic engine oil treatment

    Science.gov (United States)

    Taylan Koparan, E.; Savaskan, B.; Yanmaz, E.

    2016-08-01

    The present study focuses on the effects of standby time of the MgB2 samples immersed in synthetic engine oil on the critical current density (Jc(H)), magnetic field dependence of the pinning force density fp(b) and Tc performances of MgB2 bulk superconductors. Synthetic engine oil was used as a product which is cheap and a rich carbon source. Manufactured MgB2 pellet samples were immersed at different standby time of 30 min, 120 min, 300 min and 1440 min in synthetic engine oil after the first heating process. Finally, MgB2 samples immersed in synthetic engine oil were sintered at 1000 °C and kept for 15 min in Ar atmosphere. The critical current density of all of MgB2 samples immersed at different standby time in engine oil in whole field range was better than that of the pure MgB2 sample because of the number of the pinning centers. The MgB2 sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. The Jc value for the pure sample is 2.0 × 103 A/cm2, whereas for the MgB2 sample immersed at 300 min standby time in engine oil the Jc is enhanced to 4.8 × 103A/cm2 at 5 K and 3 T. The superconducting transition temperature (Tc) did not change with the increasing standby time of the samples in synthetic engine oil at all. The best diamagnetic property was obtained from the sample which kept in synthetic engine oil for 300 min. Synthetic engine oil treatment results in remarkable improvement of the critical current density and pinning force performances of MgB2 superconductors. It was found that all MgB2 samples have a different pinning property at different measuring temperatures. Using synthetic engine oil as a product which is cheap and a rich carbon source in MgB2 bulk superconductors makes MgB2 samples immersed in synthetic engine oil a good candidate for industrial applications.

  3. Tunneling conductance through normal metal - superconductor junctions: effects of Rashba spin orbit coupling and magnetic field

    Science.gov (United States)

    Kapri, Priyadarshini; Ganguly, Sudin; Basu, Saurabh

    2016-10-01

    In a system consisting of a metal-(s-wave) superconductor junction, we study the conductance characteristics in presence of Rashba spin orbit coupling (RSOC) and an external magnetic field applied along the plane of the sample. With a selective inclusion of the Rashba coupling either in the metallic or in both we note that there is a distinct effect with regard to the magnitude of the Andreev peak that occurs at a biasing voltage lower than the superconducting gap energy. The height of the peak is sensitive to the RSOC (increases with increase in RSOC) for RSOC to be present only in the metallic region, (same is true when RSOC is present throughout the junction), while the peak height is fairly independent when RSOC is solely present in the superconducting region. The in-plane magnetic field has very interesting effects which show up in the form of having a conductance peak at zero bias, thereby making it possible to realize a Majorana bound state.

  4. NMR in pulsed high-field magnets and application to high-T(C) superconductors.

    Science.gov (United States)

    Stork, H; Bontemps, P; Rikken, G L J A

    2013-09-01

    This article deals with the implementation of Nuclear Magnetic Resonance (NMR) experiments in pulsed magnetic fields at the pulsed-field facility of the Laboratoire National des Champs Magnétiques Intenses and its application to the high-T(C) superconductor YBa2Cu3O6.51. The experimental setup is described in detail, including a low-temperature probe head adapted for pulsed fields. An entire paragraph is dedicated to the discussion of NMR in pulsed field and the introduction of an advanced deconvolution technique making use of the induction voltage in an additional pick-up coil. The (63)Cu/(65)Cu NMR experiments on an YBa2Cu3O6.51 single crystal were performed at 2.5K during a field pulse of 46.8-T-amplitude. In the recorded spectrum the (63)Cu center line and high-frequency satellites as well as the (65)Cu center line are identified and are compared with results in literature.

  5. Characterization of high temperature superconductor cables for magnet toroidal field coils of the DEMO fusion power plant

    Energy Technology Data Exchange (ETDEWEB)

    Bayer, Christoph M.

    2017-05-01

    Nuclear fusion is a key technology to satisfy the basic demand for electric energy sustainably. The official EUROfusion schedule foresees a first industrial DEMOnstration Fusion Power Plant for 2050. In this work several high temperature superconductor sub-size cables are investigated for their applicability in large scale DEMO toroidal field coils. Main focus lies on the electromechanical stability under the influence of high Lorentz forces at peak magnetic fields of up to 12 T.

  6. Hysteretic ac loss of a superconductor strip subject to an oscillating transverse magnetic field: Geometrical and electromagnetic effects

    Science.gov (United States)

    Rauh, H.; Ma, G. T.

    2013-11-01

    Numerical simulations of geometrical and electromagnetic effects on the distributions of the magnetic induction, the electric field, the current density, the power loss density, and the hysteretic ac loss of a type-II superconductor strip exposed to an oscillating transverse magnetic field are performed by resorting to the quasistatic approximation of a vector potential approach. The underlying definition of the superconducting constituent makes use of a generalized "smoothed" Bean model of the critical state, which includes the field dependence of the induced current as well. Based on the Jacobian-free Newton-Krylov approach and the backward Euler scheme, the numerical analysis at hand is tailored to the problem of a variable width/thickness aspect ratio of the superconductor strip. Assigning representative materials characteristics and conditions of the applied magnetic field, the main findings include: (i) at high amplitudes of the applied magnetic field, variations of the magnetic induction, the induced electric field, the induced current density, and the power loss density across the thickness of the strip die away as the latter quantity abates; (ii) at low and moderate amplitudes of the applied magnetic field, the hysteretic ac loss abates rapidly, as the aspect ratio of the strip augments, the field dependence of the induced current merely playing an insignificant part thereby; conversely, whereas the geometrical effect controlled by the aspect ratio of the strip is minute at high amplitudes of the applied magnetic field, a reduction of the hysteretic ac loss occurs due to Kim's extended Ansatz for the critical state.

  7. Magnetic levitation performance of high-temperature superconductor over three magnetic hills of permanent magnet guideway with iron shims of different thicknesses

    Institute of Scientific and Technical Information of China (English)

    Yuming Gong; Gang Liang; Lifeng Zhao; Yong Zhang; Yong Zhao; Xuyong Chen

    2014-01-01

    Superconducting magnetic levitation perfor-mance, including levitation force and guidance force, is important for the application of high-temperature super-conducting maglev. Both of them are not only affected by different arrays of superconductors and magnets, but also by the thickness of the iron shim between permanent magnets. In order to obtain the best levitation performance, the magnetic field distribution, levitation force, and guid-ance force of a new type of three magnetic hills of per-manent magnet guideway with iron shim of different thicknesses (4, 6, and 8 mm) are discussed in this paper. Simulation analysis and experiment results show that the guideway with iron shim of 8 mm thickness possesses the strongest magnetic field and levitation performance when the suspension gap is larger than 10 mm. However, with the decreasing of suspension gap, the guideway with iron shim of 4 mm thickness possesses the best levitation per-formance. The phenomena can be attributed to the density distribution of flux and magnetization of iron shim.

  8. Superconductivity-induced magnetization depletion in a ferromagnet through an insulator in a ferromagnet-insulator-superconductor hybrid oxide heterostructure.

    Science.gov (United States)

    Prajapat, C L; Singh, Surendra; Paul, Amitesh; Bhattacharya, D; Singh, M R; Mattauch, S; Ravikumar, G; Basu, S

    2016-05-21

    Coupling between superconducting and ferromagnetic states in hybrid oxide heterostructures is presently a topic of intense research. Such a coupling is due to the leakage of the Cooper pairs into the ferromagnet. However, tunneling of the Cooper pairs though an insulator was never considered plausible. Using depth sensitive polarized neutron reflectivity we demonstrate the coupling between superconductor and magnetic layers in epitaxial La2/3Ca1/3MnO3 (LCMO)/SrTiO3/YBa2Cu3O7-δ (YBCO) hybrid heterostructures, with SrTiO3 as an intervening oxide insulator layer between the ferromagnet and the superconductor. Measurements above and below the superconducting transition temperature (TSC) of YBCO demonstrate a large modulation of magnetization in the ferromagnetic layer below the TSC of YBCO in these heterostructures. This work highlights a unique tunneling phenomenon between the epitaxial layers of an oxide superconductor (YBCO) and a magnetic layer (LCMO) through an insulating layer. Our work would inspire further investigations on the fundamental aspect of a long range order of the triplet spin-pairing in hybrid structures.

  9. Superconductivity-induced magnetization depletion in a ferromagnet through an insulator in a ferromagnet-insulator-superconductor hybrid oxide heterostructure

    Science.gov (United States)

    Prajapat, C. L.; Singh, Surendra; Paul, Amitesh; Bhattacharya, D.; Singh, M. R.; Mattauch, S.; Ravikumar, G.; Basu, S.

    2016-05-01

    Coupling between superconducting and ferromagnetic states in hybrid oxide heterostructures is presently a topic of intense research. Such a coupling is due to the leakage of the Cooper pairs into the ferromagnet. However, tunneling of the Cooper pairs though an insulator was never considered plausible. Using depth sensitive polarized neutron reflectivity we demonstrate the coupling between superconductor and magnetic layers in epitaxial La2/3Ca1/3MnO3 (LCMO)/SrTiO3/YBa2Cu3O7-δ (YBCO) hybrid heterostructures, with SrTiO3 as an intervening oxide insulator layer between the ferromagnet and the superconductor. Measurements above and below the superconducting transition temperature (TSC) of YBCO demonstrate a large modulation of magnetization in the ferromagnetic layer below the TSC of YBCO in these heterostructures. This work highlights a unique tunneling phenomenon between the epitaxial layers of an oxide superconductor (YBCO) and a magnetic layer (LCMO) through an insulating layer. Our work would inspire further investigations on the fundamental aspect of a long range order of the triplet spin-pairing in hybrid structures.

  10. Impact of Dynamic Orbital Correlations on Magnetic Excitations in the Normal State of Iron-Based Superconductors

    Science.gov (United States)

    Lee, Wei-Cheng; Lv, Weicheng; Tranquada, John; Phillips, Philip

    2013-03-01

    We show here that orbital degrees of freedom produce a distinct signature in the magnetic excitation spectrum of iron-based superconductors above the magnetic ordering temperature. Because dxz and dyz orbitals are strongly connected with Fermi surface topology, the nature of magnetic excitations can be modified significantly due to the presence of either static or fluctuating orbital correlations. Within a five-orbital itinerant model, we show that static orbital order generally leads to an enhancement of commensurate magnetic excitations even when the original Fermi surface lacks nesting at commensurate wavevectors. When long-range orbital order is absent, Gaussian fluctuations beyond the standard random-phase approximation capture the effects of fluctuating orbital correlations on the magnetic excitations. We find that commensurate magnetic excitations can also be enhanced if the orbital correlations are strong. We propose that this unusual incommensurate-to-commensurate transformation is an important signature to distinguish orbital from spin physics in the normal state of iron-based superconductors. This work is supported by the Center for Emergent Superconductivity, a DOE Energy Frontier Research Center, Grant No. DE-AC0298CH1088.

  11. Effect of heat capacity and conductivity of NbTi normal matrix of a composite superconductor on the stability to magnetic flux jumps

    Science.gov (United States)

    Kruglov, S. L.; Shutova, D. I.; Shcherbakov, V. I.

    2017-02-01

    The stability against magnetic flux jumps has experimentally been studied in the external magnetic field for three samples from NbTi composite superconductors, one monofilamentary and two multifilamentary. A comparison between the experiment and theory of thermomagnetic stability of composite superconductors has been carried out. We have determined threshold values of the rates of the external magnetic fields, starting from which heat capacity and conductivity of the normal composite matrix become determining stabilizing factors. For the first time, the increasing dependence of field of first magnetic flux jump on the rate of the rise in the external magnetic field has been experimentally registered in the superconducting wire for MRI. The reason for this effect is the shunting effect of a high pure copper matrix and the low volume fraction of a superconductor in the composite ( 10%).

  12. Thermodynamic scaling functions of three-dimensional anisotropic superconductors in the presence of a magnetic field with arbitrary direction

    Energy Technology Data Exchange (ETDEWEB)

    Calero, J.M. [Univ. Industrial de Santander, Bucaramanga (Colombia). Escuela de Fisica; Granada, J.C. [Dept. de Fisica, Univ. del Valle, Cali (Colombia); Silva, E.Z. da [Inst. de Fisica, Univ. Estadual de Campinas (Brazil)

    2000-07-01

    A nonperturbative method for the evaluation of thermodynamic scaling functions in the critical region of three-dimensional anisotropic type-II superconductors is extended for the case of external magnetic fields with arbitrary angles with respect to the anisotropy axis. The calculations are carried out in the framework of the Ginzburg-Landau theory. Explicit relations are obtained for the angular dependence of the magnetization and specific heat. Our theoretical results are in good agreement with experiments performed in untwinned single crystals of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. (orig.)

  13. Effect of the characteristics of a superconductor on the levitation properties of the magnet-superconductor system

    NARCIS (Netherlands)

    Rudnev, I. A.; Ermolaev, Yu. S.

    2007-01-01

    The results of the experimental and theoretical investigations of the magnetic levitation force appearing at the interaction of the multilayer superconducting block of the YBa2Cu3O7-x melted textured ceramic and a permanent magnet are presented. The maximum repulsive force and maximum attractive for

  14. Effect of the characteristics of a superconductor on the levitation properties of the magnet-superconductor system

    NARCIS (Netherlands)

    Rudnev, I. A.; Ermolaev, Yu. S.

    2007-01-01

    The results of the experimental and theoretical investigations of the magnetic levitation force appearing at the interaction of the multilayer superconducting block of the YBa2Cu3O7-x melted textured ceramic and a permanent magnet are presented. The maximum repulsive force and maximum attractive for

  15. Design and performance of a 1 MW-5 s high temperature superconductor magnetic energy storage system

    Science.gov (United States)

    Morandi, Antonio; Gholizad, Babak; Fabbri, Massimo

    2016-01-01

    The feasibility of a 1 MW-5 s superconducting magnetic energy storage (SMES) system based on state-of-the-art high-temperature superconductor (HTS) materials is investigated in detail. Both YBCO coated conductors and MgB2 are considered. A procedure for the electromagnetic design of the coil is introduced and the final layout is arrived at and compared for the two materials. The choice of the inductance of the coil is carried out as part of the design procedure. Both low-field (3 T) and high-field (8 T) designs are considered for the YBCO. AC losses during a complete charge/discharge cycle at full power are estimated and the cooling power needed for continuous operation is derived. The power conditioning system and control algorithms needed to carry out various operations are discussed in detail. Performances of the SMES system during voltage sag compensation, load leveling and power factor correction are investigated by means of numerical simulation.

  16. Vertical and lateral forces between a permanent magnet and a high-temperature superconductor

    Science.gov (United States)

    Hull, John R.; Cansiz, Ahmet

    1999-12-01

    The vertical and horizontal forces and associated stiffnesses on a permanent magnet (PM) above a high-temperature superconductor (HTS) were measured during vertical and horizontal traverses in zero-field cooling (ZFC) and in field cooling (FC). In ZFC, the vertical stiffness was greater in the first descent than in the first ascent and second descent, and the stiffness in the second descent was between those of the first descent and the first ascent. At the FC position, the vertical stiffness was two times greater than the lateral stiffness at each height, to within 1% of the vertical stiffness value. The cross stiffness of vertical force with respect to lateral position was positive for FC, but negative for ZFC. Free-spin-down experiments of a PM levitated above a HTS were also performed. These results showed that the coefficient of friction is double valued at frequencies just below the rotor resonance, a result attributed to cross stiffness in the PM/HTS interaction. A frozen-image model was used to calculate the vertical and horizontal forces and stiffnesses, and reasonable agreement with the data occurred for vertical or horizontal movements of the PM less than several mm from the FC position.

  17. Anisotropic upper critical magnetic fields in Rb2Cr3As3 superconductor

    Science.gov (United States)

    Tang, Zhang-Tu; Liu, Yi; Bao, Jin-Ke; Xi, Chuan-Ying; Pi, Li; Cao, Guang-Han

    2017-10-01

    Rb2Cr3As3 is a structurally one-dimensional superconductor containing Cr3As3 chains with a superconducting transition temperature of T_c= 4.8 K. Here we report the electrical resistance measurements for Rb2Cr3As3 single crystals, under magnetic fields up to 29.5 T and at temperatures down to 0.36 K, from which the upper critical fields, Hc2(T) , can be obtained in a broad temperature range. For field parallel to the Cr3As3 chains, Hc2\\Vert (T) is paramagnetically limited with an initial slope of μ0 dHc2\\Vert /dT\\vert Tc=-16 T K-1 and a zero-temperature upper critical field of μ0Hc2\\Vert (0)= 17.5 T. For field perpendicular to the Cr3As3 chains, however, Hc2\\bot(T) is only limited by orbital pair-breaking effect with μ0 dHc2\\perp /dT\\vert Tc=-3 T K-1 . As a consequence, the anisotropy γH=Hc2\\Vert /Hc2\\bot decreases sharply near T c and reverses below 2 K. Remarkably, the low-temperature Hc2\\bot(T) down to 0.075 Tc remains to increase linearly up to over three times the Pauli paramagnetic limit, which strongly suggests dominant spin-triplet superconductivity in Rb2Cr3As3.

  18. Magnet Lab Highlight: Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-06-05

    The alkali-doped fullerides provide the first example of a transition from a three-dimensional Mott insulator to a superconductor, enabling the effects of both dimensionality and electron correlation on superconductivity to be explored. Chemically the alkali species tunes the superconductivity in the vicinity of the the Mott transition via sample volume. Measuring the relationship between the superconducting transition temperature and upper critical field reveals a crossover from weak- to strong-coupling associated with the dynamical Jahn–Teller effect as the Mott transition is approached. The use of pulsed magnets is required because the upper critical field is enhanced in the vicinity of the Mott insulating phase, reaching 90 T for RbxCs3-xC60 — the highest among cubic crystals. This required close collaboration between Prof Kasahara’s group and the Mag Lab to design rf-measurements compatible with sample encapsulation in an inert atmosphere. The concomitant increase of pairing strength with lattice volume near the Mott transition suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity (with high-TC and high-HC2).

  19. A moving target: responding to magnetic and structural disorder in lanthanide- and actinide-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Booth, Corwin H.; Bauer, Eric D.; Mitchel, Jeremy N.

    2010-02-10

    The effects of various chemical substitutions and induced lattice disorder in the Ce- and Pu-based 115 superconductors are reviewed, with particular emphasis on results from x-ray absorption fine structure (XAFS) measurements. The PuCoGa{sub 5} system offers the opportunity to follow changes in magnetic and electronic properties due to lattice disorder as a function of time in the same samples, in addition to the more traditional approach of perturbing the superconducting state through chemical substitutions. The reviewed work establishes a baseline for such future studies by determining the intrinsic lattice order in the 115 system, successfully understanding disorder as introduced through chemical substitutions in the Ce-based 115s, and beginning to explore the surprisingly large role of self-irradiation damage directly on the PuCoGa{sub 5} lattice. These studies lay the foundation for the harder future work toward measuring chemical substitutions in PuCoGa{sub 5}, correlating effects with non-Fermi liquid behavior, and obtaining a better structural picture of the distortions induced by {alpha}-decay of the plutonium nucleus.

  20. Short wavelength fluctuation effects on the magnetization in type I and low-kappa type II superconductors

    CERN Document Server

    Mosqueira, J; Curras, S R; González, M T; Ramallo, M V; Ruibal, M; Torron, C; Vidal, F

    2003-01-01

    The effects on the magnetization of fluctuating Cooper pairs created above the superconducting transition by thermal agitation energy (the so-called fluctuation-induced diamagnetism, FD) have been measured in a clean type I superconductor (Pb) and in a clean low Ginzburg-Landau parameter (kappa) type II superconductor (Nb). These experiments extend the earlier measurements of Gollub, Beasley and Tinkham to both the high reduced temperature region (epsilon ident to ln (T/T sub C sub 0) approx> 0.1) and the high reduced magnetic field region (h ident to H/H sub C sub 2 (0) approx> 0.1). Our data show that in spite of FD being deeply affected in both superconductors by the presence of non-local electrodynamic effects, the superconducting fluctuations sharply vanish when epsilon or h become of the order of 0.5 and, respectively, 1. This short-wavelength behaviour at high reduced temperatures of the superconducting fluctuations is similar to that previously observed at high reduced temperatures in dirty low-T sub ...

  1. Combined transport, magnetization and neutron scattering study of correlated iridates and iron pnictide superconductors

    Science.gov (United States)

    Dhital, Chetan

    The work performed within this thesis is divided into two parts, each focusing primarily on the study of magnetic phase behavior using neutron scattering techniques. In first part, I present transport, magnetization, and neutron scattering studies of materials within the iridium oxide-based Ruddelsden-Popper series [Srn+1IrnO3n+1] compounds Sr 3Ir2O7 (n=2) and Sr2IrO4 (n=1). This includes a comprehensive study of the doped bilayer system Sr 3(Ir1-xRux )2O7. In second part, I present my studies of the effect of uniaxial pressure on magnetic and structural phase behavior of the iron-based high temperature superconductor Ba(Fe1-xCox)2As2. Iridium-based 5d transition metal oxides host rather unusual electronic/magnetic ground states due to strong interplay between electronic correlation, lattice structure and spin-orbit effects. Out of the many oxides containing iridium, the Ruddelsden-Popper series [Srn+1IrnO 3n+1] oxides are some of the most interesting systems to study both from the point of view of physics as well as from potential applications. My work is focused on two members of this series Sr3Ir2O 7 (n=2) and Sr2IrO4 (n=1). In particular, our combined transport, magnetization and neutron scattering studies of Sr 3Ir2O7 (n=2) showed that this system exhibits a complex coupling between charge transport and magnetism. The spin magnetic moments form a G-type antiferromagnetic structure with moments oriented along the c-axis, with an ordered moment of 0.35+/-0.06 muB/Ir. I also performed experiments doping holes in this bilayer Sr3(Ir1-xRu x)2O7 system in order to study the role of electronic correlation in these materials. Our results show that the ruthenium-doped holes remain localized within the Jeff=1/2 Mott insulating background of Sr3Ir2O7, suggestive of 'Mott blocking' and the presence of strong electronic correlation in these materials. Antiferromagnetic order however survives deep into the metallic regime with the same ordering q-vector, suggesting an

  2. Mössbauer studies of the peculiar magnetism in parent compounds of the iron-based superconductors

    Science.gov (United States)

    Jasek, A. K.; Komędera, K.; Błachowski, A.; Ruebenbauer, K.; Żukrowski, J.; Bukowski, Z.; Karpinski, J.

    2015-02-01

    A review of the magnetism in the parent compounds of the iron-based superconductors is given based on the transmission Mössbauer spectroscopy of 57Fe and 151Eu. It was found that the 3d magnetism is of the itinerant character with varying admixture of the spin-polarized covalent bonds. For the '122' compounds, a longitudinal spin density wave (SDW) develops. In the case of the EuFe2As2, a divalent europium arranges in an anti-ferromagnetical order at a much lower temperature as compared with the onset of SDW. These two magnetic systems remain almost uncoupled one to another. For the non-stoichiometric Fe1+xTe parent of the '11' family, one has a transversal SDW and magnetic order of the interstitial iron with relatively high and localized magnetic moments. These two systems are strongly coupled one to another. For the 'grand parent' of the iron-based superconductors FeAs, one observes two mutually orthogonal phase-related transversal SDW on the iron sites. There are two sets of such spin arrangements due to two crystallographic iron sites. The FeAs exhibits the highest covalency among the compounds studied, but it has still a metallic character. A contribution to XVI National Conference on Superconductivity, Zakopane, Poland, 7-12 October 2013.

  3. Fundamental properties of molecules on surfaces. Molecular switching and interaction of magnetic molecules with superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hatter, Nino

    2016-12-14

    In this thesis, we investigate individual molecular switches and metal-organic complexes on surfaces with scanning tunneling microscopy (STM) and spectroscopy (STS) at low temperatures. One focus addresses the switching ability and mechanism of diarylethene on Ag(111). The other focus lies on resolving and tuning magnetic interactions of individual molecules with superconductors. 4,4'-(4,4'-(perfluorocyclopent-1-ene-1,2-diyl)bis (5-methylthiophene-4,2-diyl)dip yridine (PDTE) is a prototypical photochromic switch. We can induce a structural change of individual PDTE molecules on Ag(111) with the STM tip. This change is accompanied by a reduction of the energy gap between the occupied and unoccupied molecular orbitals. Density functional theory (DFT) calculations reveal that the induced switching corresponds to a ring-closing reaction from an open isomer in a flat adsorption configuration to a ring-closed isomer with its methyl groups in a cis configuration. The final product is thermodynamically stabilized by strong dispersion interactions with the surface. A linear dependence of the switching threshold with the tip-sample distance with a minimal threshold of 1.4 V is found, which we assign to a combination of an electric-field induced process and a tunneling-electron contribution. DFT calculations suggest a large activation barrier for a ring-closing reaction from the open flat configuration into the closed cis configuration. The interaction of magnetic molecules with superconductors is studied on manganese phthalocyanine (MnPc) adsorbed on Pb(111). We find triplets of Shiba states inside the superconducting gap. Different adsorption sites of MnPc provide a large variety of exchange coupling strengths, which lead to a collective energy shift of the Shiba triplets. We can assign the splitting of the Shiba states to be an effect of magnetic anisotropy in the system. A quantum phase transition from a ''Kondo screened'' to a &apos

  4. Characteristic and magnetic field analysis of a high temperature superconductor axial-flux coreless induction maglev motor

    Science.gov (United States)

    Wei, Qin; Yu, Fan; Jin, Fang; Shuo, Li; Guoguo, Li; Gang, Lv

    2012-04-01

    A new high temperature superconductor axial-flux coreless maglev motor (HTS AFIM) is proposed, of which the primary windings are made of HTS tapes and the secondary is a non-magnetic conductor. The main works of this paper are the magnetic-field computation and characteristics analysis of HTS AFIM. For the first one, the reduction of magnetic fields near outer and inner radius of the HTS AFIM is solved by introducing the sub-loop electro-magnetic model along the radial position. For the second one, the AC losses of HTS coils are calculated. The relationships between the device's characteristics and device parameters are presented, and the results indicate that under certain frequency and current levitation device can output enough lift force. The conclusions are verified by finite element calculations.

  5. Characteristic and magnetic field analysis of a high temperature superconductor axial-flux coreless induction maglev motor.

    Science.gov (United States)

    Wei, Qin; Yu, Fan; Jin, Fang; Shuo, Li; Guoguo, Li; Gang, Lv

    2012-04-01

    A new high temperature superconductor axial-flux coreless maglev motor (HTS AFIM) is proposed, of which the primary windings are made of HTS tapes and the secondary is a non-magnetic conductor. The main works of this paper are the magnetic-field computation and characteristics analysis of HTS AFIM. For the first one, the reduction of magnetic fields near outer and inner radius of the HTS AFIM is solved by introducing the sub-loop electro-magnetic model along the radial position. For the second one, the AC losses of HTS coils are calculated. The relationships between the device's characteristics and device parameters are presented, and the results indicate that under certain frequency and current levitation device can output enough lift force. The conclusions are verified by finite element calculations.

  6. Enhanced trapped field performance of bulk high-temperature superconductors using split coil, pulsed field magnetization with an iron yoke

    Science.gov (United States)

    Ainslie, M. D.; Fujishiro, H.; Mochizuki, H.; Takahashi, K.; Shi, Y.-H.; Namburi, D. K.; Zou, J.; Zhou, D.; Dennis, A. R.; Cardwell, D. A.

    2016-07-01

    Investigating and predicting the magnetization of bulk superconducting materials and developing practical magnetizing techniques is crucial to using them as trapped field magnets in engineering applications. The pulsed field magnetization (PFM) technique is considered to be a compact, mobile and relative inexpensive way to magnetize bulk samples, requiring shorter magnetization times (on the order of milliseconds) and a smaller and less complicated magnetization fixture; however, the trapped field produced by PFM is generally much smaller than that of slower zero field cooling or field cooling techniques, particularly at lower operating temperatures. In this paper, the PFM of two, standard Ag-containing Gd-Ba-Cu-O samples is carried out using two types of magnetizing coils: (1) a solenoid coil, and (2) a split coil, both of which make use of an iron yoke to enhance the trapped magnetic field. It is shown that a significantly higher trapped field can be achieved using a split coil with an iron yoke, and in order to explain these how this arrangement works in detail, numerical simulations using a 2D axisymmetric finite element method based on the H -formulation are carried to qualitatively reproduce and analyze the magnetization process from both electromagnetic and thermal points of view. It is observed that after the pulse peak significantly less flux exits the bulk when the iron core is present, resulting in a higher peak trapped field, as well as more overall trapped flux, after the magnetization process is complete. The results have important implications for practical applications of bulk superconductors as such a split coil arrangement with an iron yoke could be incorporated into the design of a portable, high magnetic field source/magnet to enhance the available magnetic field or in an axial gap-type bulk superconducting electric machine, where iron can be incorporated into the stator windings to (1) improve the trapped field from the magnetization process

  7. Magnetic-Field-Induced Soft-Mode Quantum Phase Transition in the High-Temperature Superconductor La1.855Sr0.145CuO4

    DEFF Research Database (Denmark)

    Chang, J.; Christensen, Niels Bech; Niedermayer, C.

    2009-01-01

    Inelastic neutron-scattering experiments on the high-temperature superconductor La1.855Sr0.145CuO4 reveal a magnetic excitation gap Delta that decreases continuously upon application of a magnetic field perpendicular to the CuO2 planes. The gap vanishes at the critical field required to induce long...

  8. Field-induced interplanar magnetic correlations in the high-temperature superconductor La1.88Sr0.12CuO4

    DEFF Research Database (Denmark)

    Rømer, A. T.; Jensen, P.; Jacobsen, H.

    2015-01-01

    We present neutron-scattering studies of the interplanar magnetic correlations in the high-temperature superconductor La1.88Sr0.12CuO4 (Tc=27 K). The correlations are studied both in a magnetic field applied perpendicular to the CuO2 planes, and in zero field under different cooling conditions. We...

  9. The dynamics of magnetic vortices in type II superconductors with pinning sites studied by the time dependent Ginzburg–Landau model

    DEFF Research Database (Denmark)

    Sørensen, Mads Peter; Pedersen, Niels Falsig; Ögren, Magnus

    2016-01-01

    We investigate the dynamics of magnetic vortices in type II superconductors with normal state pinning sites using the Ginzburg–Landau equations. Simulation results demonstrate hopping of vortices between pinning sites, influenced by external magnetic fields and external currents. The system...

  10. Influence of the shielding currents lengthscale and anisotropy effects on the magnetic flux profiles of high-temperature superconductors

    Science.gov (United States)

    Vanderbemden, P.; Lovchinov, V.

    2012-12-01

    The so-called "magnetic flux profile" AC inductive technique is a powerful method for determining the critical current density Jc of bulk superconductors. In this work we aim at reporting analytical expressions for magnetic flux profiles of superconducting rectangular samples exhibiting a critical current density anisotropy. The results are used for examining the error resulting from approximating a rectangular cross-section by an "infinite cylinder" or "infinite slab" geometry. It is found that such approximations can lead to an artificial curvature of the flux profiles and errors of 10%-20% in the determination of Jc. Next, the effects of how planar defects (cracks, platelet boundaries,...) affect the magnetic flux profile signal are discussed. It is found that the magnetic flux profiles are much sensitive to the lengthscale of shielding currents, thereby providing means of investigation of the typical size of induced current loops in bulk superconductors. Finally some illustrative flux profile data measured on a bulk, large grain melt-processed YBCO single domain exhibiting Jc anisotropy are presented and discussed in relation with theoretical predictions.

  11. Magnetization of type-II superconductors in the form of short cylinders and the screening supercurrent distribution in the Bean model

    Science.gov (United States)

    Kuz'michev, N. D.; Fedchenko, A. A.

    2012-05-01

    The simplest analytical form of the screening supercurrent distribution is found, and the magnetization of type-II (hard) superconductors in the form of finite-length cylinders and disks (pellets) is calculated. Calculations are carried out in terms of the Bean model taking into account the curvature of magnetic field lines. From this distribution, the total magnetic field intensity and the magnetization hysteresis loop are calculated for such samples in different cases.

  12. Numerical simulation of quench protection for a 1.5 T persistent mode MgB2 conduction-cooled MRI magnet

    Science.gov (United States)

    Deissler, Robert J.; Baig, Tanvir; Poole, Charles; Amin, Abdullah; Doll, David; Tomsic, Michael; Martens, Michael

    2017-02-01

    The active quench protection of a 1.5 T MgB2 conduction-cooled MRI magnet operating in persistent current mode is considered. An active quench protection system relies on the detection of the resistive voltage developed in the magnet, which is used to trigger the external energizing of quench heaters located on the surfaces of all ten coil bundles. A numerical integration of the heat equation is used to determine the development of the temperature profile and the maximum temperature in the coil at the origin, or ‘hot spot’, of the quench. Both n-value of the superconductor and magnetoresistance of the wire are included in the simulations. An MgB2 wire manufactured by Hyper Tech Research, Inc. was used as the basis to model the wire for the simulations. With the proposed active quench protection system, the maximum temperature was limited to 200 K or less, which is considered low enough to prevent damage to the magnet. By substituting Glidcop for the Monel in the wire sheath or by increasing the thermal conductivity of the insulation, the margin for safe operation was further increased, the maximum temperature decreasing by more than 40 K. The strain on the MgB2 filaments is calculated using ANSYS, verifying that the stress and strain limits in the MgB2 superconductor and epoxy insulation are not exceeded.

  13. Magnetic Properties of GdBa{sub 2}Cu{sub 3}O{sub 7-y} Bulk Superconductors Fabricated by a Top-seeded Melt Growth Process

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K. M.; Park, S. D.; Jun, B. H.; Kim, C. J. [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Ko, T. K. [Dept. of Electrical and Eletronic Engineering, Yonsei University, Seoul (Korea, Republic of)

    2012-08-15

    The fabrications condition and superconducting properties of top-seeded melt growth (TSMG) processed GdBa{sub 2}Cu{sub 3}O{sub 7-y} (Gd123) bulk superconductors were studied. Processing parameters (a maximum temperature (T{sub max}), a temperature for crystal growth (T{sub G}) and a cooling rate (R{sub G}) through a peritectic temperature (T{sub P}) for the fabrication of single grain Gd123 superconductors were optimized. The magnetic levitation forces, trapped magnetic fields, superconducting transition temperature (Tc) and critical current density (Jc) of the Gd123 bulks superconductors were estimated. Single grain Gd123 bulk superconductors were successfully fabricated at the optimized processing condition. The Tc of a TSMG processed Gd123 sample was 92.5 K and the Jc at 77 K and 0 T was approximately 50{kappa}A/cm{sup 2}. The trapped magnetic field contour and magnetic levitation forces were dependent on the top surface morphology of TSMG processed Gd123 samples. The single grain Gd123 samples, field-cooled at 77 K using a Nd-B-Fe permanent magnet with 5.27 kG and 30 mm dia., showed the trapped magnetic field contour of a single grain with a maximum of 4 kG at the sample center. The maximum magnetic levitation forces of the single grain Gd123 sample, field-cooled or zero field-cooled, were 40 N and 107 N, respectively.

  14. Step change in equilibrium magnetization across the second magnetization peak and the peak effect region of a weakly pinned low T{sub c} superconductor, Ca{sub 3}Rh{sub 4}Sn{sub 13}

    Energy Technology Data Exchange (ETDEWEB)

    Suresh Babu, M.; Pal, D., E-mail: dpal@iitg.ac.in

    2014-09-01

    Isothermal magnetization studies in a low T{sub c} type II superconductor, Ca{sub 3}Rh{sub 4}Sn{sub 13} (T{sub c}≈8.37K), show abrupt step changes in the equilibrium magnetization lines across the second magnetization peak and the peak effect regions suggesting that both of these phenomena are first order phase transitions. We also observed two jumps in the equilibrium magnetization at two different temperature (or field) domains for a constant field (or temperature) in this low T{sub c} superconductor.

  15. Transparent magnetic state in single crystal Nd(1.85)Ce(0.15)CuO(4-y) superconductors

    Science.gov (United States)

    Zuo, F.

    1995-01-01

    Several experimental studies have been reported as evidence of Josephson coupling between the superconducting layers in the highly anisotropic oxide such as the Bi2Sr2CaCu2O8 and Tl2Ba2CuO6 systems. These include the large penetration depth of 100 mu m measured, ac and dc Josephson effects. Recently two critical temperatures corresponding to Josephson coupling in between the layers and the Berezinskii-Kosterlitz-Thouless transition in the ab-plane have been directly observed in the transport measurements. If the field is applied parallel to the superconducting layers, the magnetic excitation is not the conventional Abrikosov vortices, but the Josephson vortices which extend lambda(sub ab) in the c-axis direction and lambda(sub J) = gamma s in the plane (s is the interlayer distance, gamma is the anisotropy constant). Because of the weak screening effect associated with the Josephson vortices, there have been predictions of magnetic transparent states at magnetic field above a characteristic field H(sub J), a behavior distinctively different from that of the type-II superconductors. In this paper, we report an experimental result which illustrates a transition from the Meissner state to the magnetic transparent state in single crystal of Nd(1.85)Ce(0.15)CuO(4-y). Magnetization has been measured as a function of temperature and field in the magnetic field parallel or close to ab-plane geometry. For a fixed magnetic field, the magnetization shows a two-step transition in M(T); for a fixed temperature, the magnetization shows an abrupt change to almost zero value above a characteristic field H(sub J), an indication of magnetic transparent state. The data of magnetization as a function of field clearly deviates from the behavior predicted by the Abrikosov theory for type-II superconductors. Instead, the data fit well into the picture of Josephson decoupling between the CuO2 layers.

  16. Chiral superconductors.

    Science.gov (United States)

    Kallin, Catherine; Berlinsky, John

    2016-05-01

    Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.

  17. Evolution of Edge States and Critical Phenomena in the Rashba Superconductor with Magnetization

    Science.gov (United States)

    Yamakage, Ai; Tanaka, Yukio; Nagaosa, Naoto

    2012-02-01

    We study Andreev bound states (ABS) and the resulting charge transport of a Rashba superconductor (RSC) where two-dimensional semiconductor (2DSM) heterostructures are sandwiched by spin-singlet s-wave superconductor and ferromagnet insulator. ABS becomes a chiral Majorana edge mode in the topological phase (TP). We clarify two types of quantum criticality about the topological change of ABS near a quantum critical point (QCP), whether or not ABS exists at QCP. In the former type, ABS has an energy gap and does not cross at zero energy in the nontopological phase. These complex properties can be detected by tunneling conductance between normal metal-RSC junctions.

  18. Triplet Cooper pairs induced in diffusive s-wave superconductors interfaced with strongly spin-polarized magnetic insulators or half-metallic ferromagnets.

    Science.gov (United States)

    Ouassou, Jabir Ali; Pal, Avradeep; Blamire, Mark; Eschrig, Matthias; Linder, Jacob

    2017-05-16

    Interfacing superconductors with strongly spin-polarized magnetic materials opens the possibility to discover new spintronic devices in which spin-triplet Cooper pairs play a key role. Motivated by the recent derivation of spin-polarized quasiclassical boundary conditions capable of describing such a scenario in the diffusive limit, we consider the emergent physics in hybrid structures comprised of a conventional s-wave superconductor (e.g. Nb, Al) and either strongly spin-polarized ferromagnetic insulators (e.g. EuO, GdN) or halfmetallic ferromagnets (e.g. CrO2, LCMO). In contrast to most previous works, we focus on how the superconductor itself is influenced by the proximity effect, and how the generated triplet Cooper pairs manifest themselves in the self-consistently computed density of states (DOS) and the superconducting critical temperature T c . We provide a comprehensive treatment of how the superconductor and its properties are affected by the triplet pairs, demonstrating that our theory can reproduce the recent observation of an unusually large zero-energy peak in a superconductor interfaced with a half-metal, which even exceeds the normal-state DOS. We also discuss the recent observation of a large superconducting spin-valve effect with a T c change ~1 K in superconductor/half-metal structures, in which case our results indicate that the experiment cannot be explained fully by a long-ranged triplet proximity effect.

  19. Property and microstructural nonuniformity in the yttrium-barium-copper-oxide superconductor determined from electrical, magnetic, and ultrasonic measurements. Ph.D. Thesis - Case Western Reserve Univ.

    Science.gov (United States)

    Roth, Don J.

    1991-01-01

    The purpose of this dissertation was the following: (1) to characterize the effect of pore fraction on a comprehensive set of electrical and magnetic properties for the yttrium-barium-copper-oxide (YBCO) high temperature ceramic superconductor; and (2) to determine the viability of using a room-temperature, nondestructive characterization method to aid in the prediction of superconducting (cryogenic) properties. The latter involved correlating ultrasonic velocity measurements at room temperature with property-affecting pore fraction and oxygen content variations. The use of ultrasonic velocity for estimating pore fraction in YBCO is presented, and other polycrystalline materials are reviewed, modeled, and statistically analyzed. This provides the basis for using ultrasonic velocity to interrogate microstructure. The effect of pore fraction (0.10-0.25) on superconductor properties of YBCO samples was characterized. Spatial (within-sample) variations in microstructure and superconductor properties were investigated, and the effect of oxygen content on elastic behavior was examined. Experimental methods used included a.c. susceptibility, electrical, and ultrasonic velocity measurements. Superconductor properties measured included transition temperature, magnetic transition width, transport and magnetic critical current density, magnetic shielding, a.c. loss, and sharpness of the voltage-current characteristics. An ultrasonic velocity image constructed from measurements at 1mm increments across a YBCO sample revealed microstructural variations that correlated with variations in magnetic shielding and a.c. loss behavior. Destructive examination using quantitative image analysis revealed pore fraction to be the varying microstructural feature.

  20. Self-consistent Bogoliubov-de Gennes theory of the vortex lattice state in a two-dimensional strongly type-II superconductor at high magnetic fields

    Science.gov (United States)

    Zhuravlev, Vladimir; Duan, Wenye; Maniv, Tsofar

    2017-01-01

    A self-consistent Bogoliubov-de Gennes theory of the vortex lattice state in a 2D strong type-II superconductor at high magnetic fields reveals a novel quantum mixed state around the semiclassical Hc 2, characterized by a well-defined Landau-Bloch band structure in the quasiparticle spectrum and suppressed order-parameter amplitude, which sharply crossover into the well-known semiclassical (Helfand-Werthamer) results upon decreasing magnetic field. Application to the 2D superconducting state observed recently on the surface of the topological insulator Sb2Te3 accounts well for the experimental data, revealing a strong type-II superconductor, with unusually low carrier density and very small cyclotron mass, which can be realized only in the strong coupling superconductor limit.

  1. Ferromagnetic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Huxley, Andrew D.

    2015-07-15

    Highlights: • Review of ferromagnetic superconductors. • Covers UGe{sub 2}, URhGe and UCoGe and briefly other materials. • The focus is on experimental data and the pairing mechanism. - Abstract: The co-existence of superconductivity and ferromagnetism is of potential interest for spintronics and high magnetic field applications as well as a fascinating fundamental state of matter. The recent focus of research is on a family of ferromagnetic superconductors that are superconducting well below their Curie temperature, the first example of which was discovered in 2000. Although there is a ‘standard’ theoretical model for how magnetic pairing might bring about such a state, why it has only been seen in a few materials that at first sight appear to be very closely related has yet to be fully explained. This review covers the current state of knowledge of the magnetic and superconducting properties of these materials with emphasis on how they conform and differ from the behaviour expected from the ‘standard’ model and from each other.

  2. Ferromagnetic superconductors

    Science.gov (United States)

    Huxley, Andrew D.

    2015-07-01

    The co-existence of superconductivity and ferromagnetism is of potential interest for spintronics and high magnetic field applications as well as a fascinating fundamental state of matter. The recent focus of research is on a family of ferromagnetic superconductors that are superconducting well below their Curie temperature, the first example of which was discovered in 2000. Although there is a 'standard' theoretical model for how magnetic pairing might bring about such a state, why it has only been seen in a few materials that at first sight appear to be very closely related has yet to be fully explained. This review covers the current state of knowledge of the magnetic and superconducting properties of these materials with emphasis on how they conform and differ from the behaviour expected from the 'standard' model and from each other.

  3. Effect of nonmagnetic and magnetic impurities on the specific heat jump in anisotropic superconductors

    NARCIS (Netherlands)

    Openov, LA

    The specific-heat jump DeltaC at a critical temperature T-c in an anisotropic superconductor containing both potential and spin-flip scatterers is calculated within a weak-coupling mean-field approximation. It is shown that the presence of even a small amount of spin-flip scatterers in the sample

  4. Analysis of Magnetic Critical Fields in Iron-Based SmFeAsO0.85 HIGH-Tc Superconductor

    Science.gov (United States)

    Ahmad, Dawood; Song, Tae Kwon; Park, In Suk; Kim, G. C.; Ren, Zhi-An; Kim, Y. C.

    The magnetic properties of the newly discovered iron-oxypnictide SmFeAsO0.85 high-Tc superconductor with a Tc of around 55 K were investigated. Bulk SmFeAsO0.85 was prepared by a method for high-pressure synthesis. The lower critical field Hc1 was estimated from the magnetization at low fields; Hc1(0) was measured to be 212 Oe. A linear temperature dependence instead of saturation at low temperatures in Hc1(T) revealed unconventional superconductivity with a nodal gap structure in our SmFeAsO0.85 superconductor. The results showed that the well-known secondary peak in the temperature dependence of the critical current density Jc is absent in the SmFeAsO0.85 high-Tc superconductor. The irreversibility line Birr was fitted well by the power law dependence (1 - T/Tc)n with n ~ 1.5. This is indicative of the flux creep phenomena in the SmFeAsO0.85 high-Tc superconductor. In addition, within the range of measurement temperatures in this study, no crossover was observed in the temperature dependence of the irreversibility line Birr which may be due to low anisotropy in our SmFeAsO0.85 superconductor.

  5. Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Laurent, P; Vanderheyden, B; Vanderbemden, P [SUPRATECS and Department of Electrical Engineering and Computer Science B28, Sart-Tilman, B-4000 Liege (Belgium); Fagnard, J-F [SUPRATECS, Royal Military Academy of Belgium, Avenue de la Renaissance, B-1000 Brussels (Belgium); Babu, N Hari [Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University, West London UB8 3PH (United Kingdom); Cardwell, D A, E-mail: Philippe.Vanderbemden@ulg.ac.b [Bulk Superconductivity Group, Engineering Department, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)

    2010-12-15

    In this work we study, both experimentally and numerically, the self-heating of a bulk, large YBCO pellet of aspect ratio (thickness/diameter) {approx} 0.4 subjected to a large AC magnetic field. To ensure accurate temperature measurements, the sample was placed in an experimental vacuum chamber to achieve a small and reproducible heat transfer coefficient between the superconductor and the cryogenic fluid. The temperature was measured at several locations on the sample surface during the self-heating process. The experimentally determined temperature gradients are found to be very small in this arrangement (<0.2 K across the radius of the superconductor). The time-dependence of the average temperature T(t) is found to agree well with a theoretical prediction based on the one-dimensional (1D) Bean model, assuming a uniform temperature in the sample. A 2D magneto-thermal model was also used to determine the space and time-dependent temperature distribution T(r, z, t) during the application of the AC field. The losses in the bulk pellet were determined using an algorithm based on the numerical method of Brandt, which was combined with a heat diffusion algorithm implemented using a finite-difference method. The model is shown to be able to reproduce the main trends of the observed temperature evolution of the bulk sample during a self-heating process. Finally, the 2D model is used to study the effect of a non-uniform distribution of critical current density J{sub c}(r, z) on the losses within the bulk superconductor.

  6. Orbital and spin moments in the ferromagnetic superconductor URhGe by x-ray magnetic circular dichroism

    Science.gov (United States)

    Wilhelm, F.; Sanchez, J. P.; Brison, J.-P.; Aoki, D.; Shick, A. B.; Rogalev, A.

    2017-06-01

    The ferromagnetic superconductor URhGe has been investigated by high field magnetic circular dichroism (XMCD) at the U M4 ,5, Rh L2 ,3, and Ge K edges at 2.1 K and at applied fields up to 17 T. The XMCD performed at the M4 ,5 absorption edges allows us to determine the spectroscopic branching ratio and the 5 f electron contribution to the valence spin-orbit interaction. Combination with polarized neutron diffraction results allows us to derive the individual U orbital and spin moments and the magnetic-dipole contribution . There is no evidence for any change of the orbital-to-spin moment ratios across the spin reorientation transition at HR=12 T , when the field is applied along the initial hard b axis. We also confirm that the magnetism of URhGe is dominated by U , with the contribution of Rh representing only about 10 % of the macroscopic moment. The orbital and spin moments at the Rh site are found to be parallel to each other and parallel to the macroscopic magnetization, but an unexpectedly large orbital-to-spin moment ratio is observed. The XMCD at the Ge K edge reveals the presence of a small induced Ge 4 p orbital moment, parallel to the macroscopic magnetization. The results are discussed against predictions of the electronic band structure calculations by the density functional theory plus Coulomb U , including spin-orbit coupling (DFT +U +SOC ) .

  7. Persistence

    Science.gov (United States)

    Moore, John W.

    1998-11-01

    Eudora Welty, the famous writer, was once asked what should be done by society or government to encourage young writers. Her response, which surprised the questioner, and me when I heard it, was "Nothing". Welty contended that a person who was really a writer would be persistent enough to overcome whatever obstacles were in the way, needing no interference or support from others.

  8. Influence of a magnetic field on the thermal conductivity of d-wave high-T sub c superconductors

    CERN Document Server

    Houssa, M

    1997-01-01

    The influence of a magnetic field on the electronic contribution k sub e to the thermal conductivity of a d-wave superconductor is described. We use the kinetic expression for k sub e in terms of a number of carriers deduced from the electronic specific heat of a d-wave superconductor. We calculate the field and temperature dependence of the scattering rate of normal heat-carrying electrons scattered by quasi-particle excitations in the 2D-like vortex cores. Near T sub c , the experimental results on various YBa sub 2 Cu sub 3 O sub 7 sub - subdelta and Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 samples are quite well reproduced by this model, as in the s-wave case with a small difference between the deduced physical parameters. However, experimental results on the field dependence of the thermal conductivity at very low temperatures are shown to be incompatible with an s-wave gap parameter but can be explained by considering a d-wave order parameter. More reasonable parameter values are found herein. (author)

  9. Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

    Science.gov (United States)

    Laurent, P.; Fagnard, J.-F.; Babu, N. Hari; Cardwell, D. A.; Vanderheyden, B.; Vanderbemden, P.

    2010-12-01

    In this work we study, both experimentally and numerically, the self-heating of a bulk, large YBCO pellet of aspect ratio (thickness/diameter) ~ 0.4 subjected to a large AC magnetic field. To ensure accurate temperature measurements, the sample was placed in an experimental vacuum chamber to achieve a small and reproducible heat transfer coefficient between the superconductor and the cryogenic fluid. The temperature was measured at several locations on the sample surface during the self-heating process. The experimentally determined temperature gradients are found to be very small in this arrangement (Bean model, assuming a uniform temperature in the sample. A 2D magneto-thermal model was also used to determine the space and time-dependent temperature distribution T(r, z, t) during the application of the AC field. The losses in the bulk pellet were determined using an algorithm based on the numerical method of Brandt, which was combined with a heat diffusion algorithm implemented using a finite-difference method. The model is shown to be able to reproduce the main trends of the observed temperature evolution of the bulk sample during a self-heating process. Finally, the 2D model is used to study the effect of a non-uniform distribution of critical current density Jc(r, z) on the losses within the bulk superconductor.

  10. Significant flux trapping in single grain GdBCO bulk superconductor under off-axis field cooled magnetization

    Science.gov (United States)

    Li, Zhi; Ida, Tetsuya; Miki, Motohiro; Teshima, Hidekazu; Morita, Mitsuru; Izumi, Mitsuru

    2017-03-01

    A single grain bulk high-temperature superconductor (HTS) exhibits intensified flux trapping performance upon field cooled magnetization. The world record of trapped flux is 17.6 T achieved by using stacked two-fold GdBCO bulks. However, the majority of magnetization studies focused on the magnetization along the crystallographic c-axis. In the present study, we clarify the flux trapping performance under field cooled magnetization using an off-axis magnetic field with respect to the c-axis. The results show that the trapped flux is almost polarized along the applied field as expected. This tendency remains up to a high off-axis angle θ around 60°. It is worth mentioning that, with θ of 30°, the maximum trapped flux component B // max parallel to the c-axis significantly remains more than 96% of 1.6 T which occurs under on-axis magnetization. Meanwhile, the angular dependence of the c-axis parallel component exhibits that observed flux density is higher than that expected from 1.6 cosθ. In addition, to visualize the flux line upon magnetization at θ of 90°, we successfully demonstrate the continuous flux line trace using steel wires; different trapped flux behaviour appears when applied field penetrates the bulk through the growth sectors centre and along the growth sector boundary, respectively. We interpret these results may come from the microstructure as a result of melt growth. It is highly emphasized that the off-axis magnetization with the finite inclination angle is quite useful for introducing into the design of HTS applications.

  11. Studies of two-dimensional MoGe superconductors in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kapitulnik, A. (Stanford Univ., CA (United States). Dept. of Applied Physics); Yazdani, A. (Stanford Univ., CA (United States). Dept. of Applied Physics); Urbach, J.S. (Stanford Univ., CA (United States). Dept. of Applied Physics); White, W.R. (Stanford Univ., CA (United States). Dept. of Applied Physics); Beasley, M.R. (Stanford Univ., CA (United States). Dept. of Applied Physics)

    1994-03-01

    The H-T phase diagram of two-dimensional amorphous MoGe superconductors is studied near H[sub c2] and near the melting line of the vortex lattice. Good agreement with the lowest Landau level approximation is found for the broadening of the specific heat in a field. We also find that melting of the vortex lattice can be observed only on short enough length scales, shorter than the disorder-mediated lattice correlation length. (orig.)

  12. Nematic quantum critical point without magnetism in FeSe1-xSx superconductors

    Science.gov (United States)

    Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

    2016-07-01

    In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near ≈0.17, the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.

  13. Nematic quantum critical point without magnetism in FeSe1-xSx superconductors.

    Science.gov (United States)

    Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

    2016-07-19

    In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near [Formula: see text], the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.

  14. Superconducting Accelerator Magnets

    CERN Document Server

    Mess, K H; Wolff, S

    1996-01-01

    The main topic of the book are the superconducting dipole and quadrupole magnets needed in high-energy accelerators and storage rings for protons, antiprotons or heavy ions. The basic principles of low-temperature superconductivity are outlined with special emphasis on the effects which are relevant for accelerator magnets. Properties and fabrication methods of practical superconductors are described. Analytical methods for field calculation and multipole expansion are presented for coils without and with iron yoke. The effect of yoke saturation and geometric distortions on field quality is studied. Persistent magnetization currents in the superconductor and eddy currents the copper part of the cable are analyzed in detail and their influence on field quality and magnet performance is investigated. Superconductor stability, quench origins and propagation and magnet protection are addressed. Some important concepts of accelerator physics are introduced which are needed to appreciate the demanding requirements ...

  15. Thickness dependence of the levitation performance of double-layer high-temperature superconductor bulks above a magnetic rail

    Energy Technology Data Exchange (ETDEWEB)

    Sun, R.X.; Zheng, J.; Liao, X.L.; Che, T.; Gou, Y.F.; He, D.B.; Deng, Z.G., E-mail: zgdeng@gmail.com

    2014-10-15

    Highlights: • Thickness optimization of double-layer bulk HTSC arrangement is studied. • The new bulk HTSC arrangement makes better use of the flux distribution of the magnetic rails. • Levitation performance can be enhanced with the optimization. • The optimization can meet large levitation force requirements for HTS Maglev system. - Abstract: A double-layer high-temperature superconductor (HTSC) arrangement was proposed and proved to be able to bring improvements to both levitation force and guidance force compared with present single-layer HTSC arrangement. To fully exploit the applied magnetic field by a magnetic rail, the thickness dependence of a double-layer HTSC arrangement on the levitation performance was further investigated in the paper. In this study, the lower-layer bulk was polished step by step to different thicknesses, and the upper-layer bulk with constant thickness was directly superimposed on the lower-layer one. The levitation force and the force relaxation of the double-layer HTSC arrangement were measured above a Halbach magnetic rail. Experimental result shows that a bigger levitation force and a less levitation force decay could be achieved by optimizing the thickness of the lower-layer bulk HTSC. This thickness optimization method could be applied together with former reported double-layer HTSC arrangement method with aligned growth sector boundaries pattern. This series of study on the optimized combination method do bring a significant improvement on the levitation performance of present HTS maglev systems.

  16. Effect of magnetic and nonmagnetic nano metal oxides doping on the critical temperature of a YBCO superconductor

    Science.gov (United States)

    Salama, A. H.; El-Hofy, M.; Rammah, Y. S.; Elkhatib, M.

    2015-12-01

    Bulk superconductor samples of YBa2Cu3O7-δ (YBCO) doped with nano metal oxides of Mn3O4, Co3O4, Cr2O3, CuO and SnO2 respectively with 0.2 wt% are synthesized by a solid-state reaction route. The structural characterization of all samples has been carried out by x-ray diffraction (XRD) and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The XRD patterns indicate that the magnetic doping of nano metal oxides ≤ft({{{Mn}}}{{3}}{{{O}}}{{4}}, {{{Co}}}{{3}}{{{O}}}{{4}}, {{{Cr}}}{{2}}{{{O}}}{{3}}\\right) gives a high value of orthorhombicity of the YBCO samples which is the result of high oxygen content, and consequently could give better superconducting properties contrary to the non magnetic nano oxides (CuO, SnO2). The critical temperature (Tc) of the studied samples was found to improve by nano magnetic doping and lower with nano nonmagnetic doping. The superconducting transition temperature Tc determined from electrical resistivity measurements was found to increase for Mn3O4 (5.27 μB) doping and decrease for other metal oxides doping.

  17. Thickness dependence of the levitation performance of double-layer high-temperature superconductor bulks above a magnetic rail

    Science.gov (United States)

    Sun, R. X.; Zheng, J.; Liao, X. L.; Che, T.; Gou, Y. F.; He, D. B.; Deng, Z. G.

    2014-10-01

    A double-layer high-temperature superconductor (HTSC) arrangement was proposed and proved to be able to bring improvements to both levitation force and guidance force compared with present single-layer HTSC arrangement. To fully exploit the applied magnetic field by a magnetic rail, the thickness dependence of a double-layer HTSC arrangement on the levitation performance was further investigated in the paper. In this study, the lower-layer bulk was polished step by step to different thicknesses, and the upper-layer bulk with constant thickness was directly superimposed on the lower-layer one. The levitation force and the force relaxation of the double-layer HTSC arrangement were measured above a Halbach magnetic rail. Experimental result shows that a bigger levitation force and a less levitation force decay could be achieved by optimizing the thickness of the lower-layer bulk HTSC. This thickness optimization method could be applied together with former reported double-layer HTSC arrangement method with aligned growth sector boundaries pattern. This series of study on the optimized combination method do bring a significant improvement on the levitation performance of present HTS maglev systems.

  18. Amplitude effect of internal friction associated with magnetic flux pinning in YBa 2Cu 3O 7- x superconductor

    Science.gov (United States)

    Wen, Y. T.; Kê, T. S.; Bohn, H. G.; Soltner, H.; Schilling, W.

    1992-04-01

    The amplitude effect of internal friction associated with magnetic flux pinning in high- Tc bulk and film YBa 2Cu 3O 7- superconductors were investigated by the vibrating reed technique. It was found that Q-B exhibits an anomalous amplitude effect at low temperature, weak applied magnetic field and small vibration amplitude, and exhibits a normal amplitude effect at high temperature, strong applied magnetic field and large vibration amplitude. Both anomalous and normal amplitude effects of Q-1B were found for a bulk specimen, but only an anomalous amplitude effect of Q-B for a film specimen. This amplitude effect of Q-1B reflects the variation of the state of motion and the process of pinning and depinning of the flux lines during the vibration of the specimen. The resonant frequency fr was found to be independent of Am within the measured amplitude range. It is considered that the variation of fr with Ba is mainly associated with the diamagnetism of the specimen.

  19. Granular Superconductors and Gravity

    Science.gov (United States)

    Noever, David; Koczor, Ron

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with a relatively high percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 104 was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field and exposed without levitation to low-field strength AC magnetic fields. Changes in observed gravity signals were measured to be less than 2 parts in 108 of the normal gravitational acceleration. Given the high sensitivity of the test, future work will examine variants on the basic magnetic behavior of granular superconductors, with particular focus on quantifying their proposed importance to gravity.

  20. Magnetization of the joint-free high temperature superconductor (REBa2Cu3Ox coil by field cooling

    Directory of Open Access Journals (Sweden)

    Yali Zheng

    2017-09-01

    Full Text Available Joint-free (REBa2Cu3Ox (REBCO coil based on ‘wind-and-flip’ technique has been developed to generate a persistent magnetic field without power supply. This paper is to study the magnetization characteristics of the joint-free REBCO coil by field cooling, in order to trap higher field. A joint-free pancake coil is wound by REBCO tapes and the field cooling magnetization test is performed on it. An approximate numerical model based on H-formulation is built for this coil to analyze its magnetization behavior, which is validated by the experimental results Analysis show that a persistent direct current is induced in the coil during the field cooling operation, which generates the trapped field. The induced current of the joint-free coil shows an intrinsic non-uniform distribution among turns. Increasing the magnetization field and critical current of REBCO conductors can considerably increase the trapped field. But the trapping factor (the rate of trapped field to background magnetization field reaches a maximum value (60 % for the test coil. This maximum value is an intrinsic characteristics for a fabricated coil, which only depends on the coil’s geometry structure. With a same usage of REBCO tapes, the trapping factor can be improved significantly by optimizing the coil structure to multiple pancakes, and it can approach 100 %.

  1. Current status of iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kamihara, Yoichi, E-mail: kamihara_yoichi@appi.keio.ac.jp [Keio University, Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology (Japan)

    2012-03-15

    Current status of iron-based superconductors is summarized. Although short range magnetic ordering and magnetic phase separation of Fe are controversial, (long range) magnetic and electronic phase diagrams of iron based superconductors can be classified into two-type. Antiferromagnetic ordering of itinerant Fe does not coexist with superconducting phase of SmFeAsO{sub 1 - x}F{sub x}. The very large H{sub c2} of iron-based superconductors attract us to attempts at applications.

  2. Current status of iron-based superconductors

    Science.gov (United States)

    Kamihara, Yoichi

    2012-03-01

    Current status of iron-based superconductors is summarized. Although short range magnetic ordering and magnetic phase separation of Fe are controversial, (long range) magnetic and electronic phase diagrams of iron based superconductors can be classified into two-type. Antiferromagnetic ordering of itinerant Fe does not coexist with superconducting phase of SmFeAsO1 - xFx. The very large H c2 of iron-based superconductors attract us to attempts at applications.

  3. Development of superconductor bulk for superconductor bearing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chan Joong; Jun, Byung Hyuk; Park, Soon Dong (and others)

    2008-08-15

    Current carrying capacity is one of the most important issues in the consideration of superconductor bulk materials for engineering applications. There are numerous applications of Y-Ba-Cu-O (YBCO) bulk superconductors e.g. magnetic levitation train, flywheel energy storage system, levitation transportation, lunar telescope, centrifugal device, magnetic shielding materials, bulk magnets etc. Accordingly, to obtain YBCO materials in the form of large, single crystals without weak-link problem is necessary. A top seeded melt growth (TSMG) process was used to fabricate single crystal YBCO bulk superconductors. The seeded and infiltration growth (IG) technique was also very promising method for the synthesis of large, single-grain YBCO bulk superconductors with good superconducting properties. 5 wt.% Ag doped Y211 green compacts were sintered at 900 .deg. C {approx} 1200 .deg.C and then a single crystal YBCO was fabricated by an infiltration method. A refinement and uniform distribution of the Y211 particles in the Y123 matrix were achieved by sintering the Ag-doped samples. This enhancement of the critical current density was ascribable to a fine dispersion of the Y211 particles, a low porosity and the presence of Ag particles. In addition, we have designed and manufactured large YBCO single domain with levitation force of 10-13 kg/cm{sup 2} using TSMG processing technique.

  4. Hysteresis losses in MgB2 superconductors exposed to combinations of low AC and high DC magnetic fields and transport currents

    DEFF Research Database (Denmark)

    Magnusson, N.; Abrahamsen, Asger Bech; Liu, Dawei

    2014-01-01

    a simplified theoretical treatment of the hysteresis losses based on available models in the literature with the aim of setting the basis for estimation of the allowable magnetic fields and current ripples in superconducting generator coils intended for large wind turbine direct drive generators. The resulting...... equations use the DC in-field critical current, the geometry of the superconductor and the magnitude of the AC magnetic field component as parameters. This simplified approach can be valuable in the design of MgB2 DC coils in the 1–4T range with low AC magnetic field and current ripples....

  5. Fabrication and Properties of Aligned Sr0.6K0.4Fe2As2 Superconductors by High Magnetic Field Processing

    Institute of Scientific and Technical Information of China (English)

    GAO Zhao-Shun; WATANABE Kazuo; ZHANG Xian-Ping; WANG Dong-Liang; QI Yan-Peng; WANG Lei; CHENG Jun-Sheng; WANG Qiu-Liang; MA Yan-Wei; AWAJI Satoshi

    2011-01-01

    @@ We fabricated a c-axis aligned SrKFeAs superconductor using a two-step magnetic field procedure.The effect of the magnetic fields on the structure and superconducting properties of SrKFeAs is investigated using x-ray diffraction and magnetic measurements.The degree of orientation of the samples is about 0.39 for the c axis and 0.51 for ab-plane orientation, as evaluated from the Lotgering factor of x-ray diffraction.This technology may be useful in a variety of potential applications, including preparing iron-based superconducting bulks and wires with high critical currents.

  6. Study of local structure and magnetism in high-T(sub c) copper oxide superconductors

    Science.gov (United States)

    Budnick, J. I.; Tan, Z.; Filipkowski, M.; Niedermayer, CH.; Glueckler, H.; Simon, R.; Golnik, A.; Rauer, M.; Recknagel, E.; Weidinger, A.

    1990-01-01

    The muon spin rotation (MUSR) study of local magnetism of Sr-doped La2CuO4 is reviewed. Emphasis is placed on magnetic order as detected by local and bulk probes with local atomic environments studied by x ray absorption fine structure (XAFS). Correlations between the MUSR study of local magnetic ordering and the bulk magnetization study are presented along with a discussion of the dependence upon oxygen stoichiometry. Results are presented for both superconducting phases and magnetic phases. Recent data which reveals the existence of local magnetic ordering in the hydrogen-doped YBa2Cu3O7 system are also discussed.

  7. High temperature superconductors: A technological revolution

    Science.gov (United States)

    1990-01-01

    The objectives are to demonstrate the Meissner effect through magnetic levitation, to demonstrate one application of the Meissner effect, the low friction magnetic rotation bearing, and to demonstrate magnetic flux penetration and the Type II nature of ceramic superconductors via the stacking of the superconductor disks. Experimental equipment and procedures are described.

  8. Consistent behaviour of AC susceptibility and transport properties in magnetic superconductor RuSr 2GdCu 2O 8

    Science.gov (United States)

    Očko, M.; Živkovic, I.; Prester, M.; Drobac, Dj.; Ariosa, D.; Berger, H.; Pavuna, D.

    2004-02-01

    We report on AC susceptibility, resistivity, thermopower and measurements of sintered magnetic superconductor RuSr 2GdCu 2O 8. The antiferromagnetic phase transition at 133 K is seen clearly in the AC susceptibility as well as in the derivative of resistivity and thermopower. Above the antiferromagnetic transition, we have found some new evidences of the similarity between HTC compounds and the magnetic superconductor. The onset of superconductivity is observed by both transport methods at 46 K, and an explanation why it is not seen in the AC susceptibility data is given. The end of the SC transition occurs at about 24 K in all measured properties. We discuss the steps of broad SC transition, especially the maximum in susceptibility at 34 K, and compare our results with related studies reported in the literature.

  9. Consistent behaviour of AC susceptibility and transport properties in magnetic superconductor RuSr{sub 2}GdCu{sub 2}O{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Ocko, M. E-mail: ocko@ifs.hr; Zivkovic, I.; Prester, M.; Drobac, Dj.; Ariosa, D.; Berger, H.; Pavuna, D

    2004-02-01

    We report on AC susceptibility, resistivity, thermopower and measurements of sintered magnetic superconductor RuSr{sub 2}GdCu{sub 2}O{sub 8}. The antiferromagnetic phase transition at 133 K is seen clearly in the AC susceptibility as well as in the derivative of resistivity and thermopower. Above the antiferromagnetic transition, we have found some new evidences of the similarity between HTC compounds and the magnetic superconductor. The onset of superconductivity is observed by both transport methods at 46 K, and an explanation why it is not seen in the AC susceptibility data is given. The end of the SC transition occurs at about 24 K in all measured properties. We discuss the steps of broad SC transition, especially the maximum in susceptibility at 34 K, and compare our results with related studies reported in the literature.

  10. Simulation of dc magnetic effects due to geometrically defined grain boundaries in type-II superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bartolome, E. [Escola Universitaria Salesiana de Sarria, Passeig Sant Joan Bosco, 74, 08017 Barcelona (Spain)], E-mail: ebartolome@euss.es; Granados, X.; Bozzo, B. [Institut de Ciencia de Materials de Barcelona, CSIC, Campus UAB, 08193 Bellaterra (Spain); Navau, C. [Grup d' Electromagnetisme, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Puig, T.; Obradors, X. [Institut de Ciencia de Materials de Barcelona, CSIC, Campus UAB, 08193 Bellaterra (Spain)

    2008-03-30

    A Bean model-based program ('Trazacorrientes') has been used to simulate the current distribution in the saturated remanent state of type-II superconducting bicrystal-like squared samples. The grain boundary was modeled by a set of periodically spaced holes geometrically defining the current transparency. Current simulations performed as a function of the boundary transparency, width and geometry are analyzed. Current distributions agree qualitatively with previously reported imaging measurements, while quantitative results can be obtained with an accuracy of {approx}5% due to present computing resolution limits. Thanks to 'Trazacorrientes' easy way of implementing irregular defects, meandering grain boundaries formed by straight facets of different local transparency could be simulated. The advantages and disadvantages of the program for the simulation of type-II superconductors with defects, among which GB's, are discussed.

  11. Frequency dependence of magnetic hysteresis in the field-induced microwave absorption in high T/sub c/ superconductors at T << T/sub c/

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, S.; Gould, A.; Shaw, G.; Bhagat, S.M.; Manheimer, M.A.

    1989-04-24

    The high T/sub c/ superconductors Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ and Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/ exhibit magnetic hysteresis in the field-induced microwave absorption at low temperatures (T< or approx.16 K). The ''coercive field'' shows a very strong dependence on frequency.

  12. Finite Element Treatment of Vortex States in 3D Cubic Superconductors in a Tilted Magnetic Field

    Science.gov (United States)

    Peng, Lin; Cai, Chuanbing

    2017-03-01

    The time-dependent Ginzburg-Landau equations have been solved numerically by a finite element analysis for superconducting samples with a cubic shape in a tilted magnetic field. We obtain different vortex patterns as a function of the external magnetic field. With a magnetic field not parallel to the x- or y-axis, the vortices attempt to change their orientation accordingly. Our analysis of the corresponding changes in the magnetic response in different directions can provide information not only about vorticity but also about the three-dimensional vortex arrangement, even about the very subtle changes for the superconducting samples with a cubic shape in a tilted magnetic field.

  13. A Double-Decker Levitation Experiment Using a Sandwich of Superconductors.

    Science.gov (United States)

    Jacob, Anthony T.; And Others

    1988-01-01

    Shows that the mutual repulsion that enables a superconductor to levitate a magnet and a magnet to levitate a superconductor can be combined into a single demonstration. Uses an overhead projector, two pellets of "1-2-3" superconductor, Nd-Fe-B magnets, liquid nitrogen, and paraffin. Offers superconductor preparation, hazards, and disposal…

  14. Remagnetization of bulk high-temperature superconductors subjected to crossed and rotating magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Vanderbemden, P [SUPRATECS and Department of Electrical Engineering and Computer Science B28, Sart-Tilman, B-4000 Liege (Belgium); Hong, Z [Centre for Advanced Photonics and Electronics, Engineering Department, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Coombs, T A [Centre for Advanced Photonics and Electronics, Engineering Department, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Ausloos, M [SUPRATECS and Department of Physics B5, Sart-Tilman, B-4000 Liege (Belgium); Babu, N Hari [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Cardwell, D A [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Campbell, A M [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom)

    2007-09-15

    Bulk melt-processed Y-Ba-Cu-O (YBCO) has significant potential for a variety of high-field permanent-magnet-like applications, such as the rotor of a brushless motor. When used in rotating devices of this kind, however, the YBCO can be subjected to both transient and alternating magnetic fields that are not parallel to the direction of magnetization and which have a detrimental effect on the trapped field. These effects may lead to long-term decay of the magnetization of the bulk sample. In the present work, we analyze both experimentally and numerically the remagnetization process of a melt-processed YBCO single domain that has been partially demagnetized by a magnetic field applied orthogonal to the initial direction of trapped flux. Magnetic torque measurements are used as a tool to probe changes in the remanent magnetization during various sequences of applied field. The application of a small magnetic field between the transverse cycles parallel to the direction of original magnetization results in partial remagnetization of the sample. Rotating the applied field, however, is found to be much more efficient at remagnetizing the bulk material than applying a magnetizing field pulse of the same amplitude. The principal features of the experimental data can be reproduced qualitatively using a two-dimensional finite-element numerical model based on an E-J power law. Finally, the remagnetization process is shown to result from the complex modification of current distribution within the cross-section of the bulk sample.

  15. Magnetic levitation and its application for education devices based on YBCO bulk superconductors

    Science.gov (United States)

    Yang, W. M.; Chao, X. X.; Guo, F. X.; Li, J. W.; Chen, S. L.

    2013-10-01

    A small superconducting maglev propeller system, a small spacecraft model suspending and moving around a terrestrial globe, several small maglev vehicle models and a magnetic circuit converter have been designed and constructed. The track was paved by NdFeB magnets, the arrangement of the magnets made us easy to get a uniform distribution of magnetic field along the length direction of the track and a high magnetic field gradient in the lateral direction. When the YBCO bulks mounted inside the vehicle models or spacecraft model was field cooled to LN2 temperature at a certain distance away from the track, they could be automatically floating over and moving along the track without any obvious friction. The models can be used as experimental or demonstration devices for the magnetic levitation applications.

  16. THE PROPERTIES AND MICROSTRUCTURE OF NB-47TI SUPERCONDUCTOR WITH MAGNETIC PINNING CENTERS.

    Energy Technology Data Exchange (ETDEWEB)

    MOTOWIDLO,L.R.RUDZIAK,M.D.WONG,T.COOLEY,L.D.LEE,P.J.

    2004-02-04

    We have investigated Nb-47Ti multifilament wire with artificial pinning centers (APC). The superconducting properties and proximity effect in wires with ferromagnetic and non-magnetic pins will be discussed. Magnetization and transport measurements will be presented and the pinning characteristics will be discussed as a function of magnetic field, temperature and volume percent pins. In addition, field emission scanning electron microscopy of the pin nanostructure will be presented.

  17. Magnetic flux pinning in superconductors with hyperbolic-tessellation arrays of pinning sites

    Science.gov (United States)

    Misko, V. R.; Nori, Franco

    2012-05-01

    We study magnetic flux interacting with arrays of pinning sites (APSs) placed on vertices of hyperbolic tessellations (HTs). We show that, due to the gradient in the density of pinning sites, HT APSs are capable of trapping vortices for a broad range of applied magnetic fluxes. Thus, the penetration of magnetic field in HT APSs is essentially different from the usual scenario predicted by the Bean model. We demonstrate that, due to the enhanced asymmetry of the surface barrier for vortex entry and exit, this HT APS could be used as a “capacitor” to store magnetic flux.

  18. Hysteresis losses in MgB{sub 2} superconductors exposed to combinations of low AC and high DC magnetic fields and transport currents

    Energy Technology Data Exchange (ETDEWEB)

    Magnusson, N., E-mail: niklas.magnusson@sintef.no [SINTEF Energy Research, NO-7465 Trondheim (Norway); Abrahamsen, A.B. [DTU Wind Energy, Technical University of Denmark, DK-4000 Roskilde (Denmark); Liu, D. [Electrical Power Processing Group, TU Delft, Mekelweg 4, NL-2628 CD Delft (Netherlands); Runde, M. [SINTEF Energy Research, NO-7465 Trondheim (Norway); Polinder, H. [Electrical Power Processing Group, TU Delft, Mekelweg 4, NL-2628 CD Delft (Netherlands)

    2014-11-15

    Highlights: • A method for calculating hysteresis losses in the low AC – high DC magnetic field and transport current range has been shown. • The method can be used in the design of wind turbine generators for calculating the losses in the generator DC rotor. • First estimates indicate tolerable current ripple in the 0.1% range for a 4 T DC MgB{sub 2} generator rotor coil. - Abstract: MgB{sub 2} superconductors are considered for generator field coils for direct drive wind turbine generators. In such coils, the losses generated by AC magnetic fields may generate excessive local heating and add to the thermal load, which must be removed by the cooling system. These losses must be evaluated in the design of the generator to ensure a sufficient overall efficiency. A major loss component is the hysteresis losses in the superconductor itself. In the high DC – low AC current and magnetic field region experimental results still lack for MgB{sub 2} conductors. In this article we reason towards a simplified theoretical treatment of the hysteresis losses based on available models in the literature with the aim of setting the basis for estimation of the allowable magnetic fields and current ripples in superconducting generator coils intended for large wind turbine direct drive generators. The resulting equations use the DC in-field critical current, the geometry of the superconductor and the magnitude of the AC magnetic field component as parameters. This simplified approach can be valuable in the design of MgB{sub 2} DC coils in the 1–4 T range with low AC magnetic field and current ripples.

  19. Simulation of magnetization and levitation properties of arrays of ring-shaped type-II superconductors

    Science.gov (United States)

    Liu, Jun; Huang, Chenguang; Yong, Huadong; Zhou, Youhe

    2017-03-01

    This paper presents an analysis of the magnetic and mechanical properties of arrays of superconducting rings arranged in axial, radial, and matrix configurations under different magnetic fields. In terms of the Bean's critical state model and the minimum magnetic energy method, the dependences of the magnetization and levitation behaviors on the geometry, number, and gap of the superconducting rings are obtained. The results show that when the applied field is spatially uniform, the magnetic property of the superconducting array is associated with the gaps between the rings. For the case of small gaps, the entire array becomes not easy to be fully penetrated by the induced currents, and the magnetic field profiles of which are almost the same as ones in a single large ring. If the superconducting array is fully penetrated, its saturation magnetization value is affected by the radial interval and, however, is almost independent of the vertical separation. When the applied field produced by a cylindrical permanent magnet is nonuniform, the superconducting array will be subjected to a levitation force. The levitation force increases monotonically and finally reaches a saturation value with increasing height or thickness of the rings, and such saturation value is closely related to the inner radius of the array.

  20. Magnetization of Gd diffused YBa2Cu3O7-x superconductor:Experiment and theory

    Institute of Scientific and Technical Information of China (English)

    F.Inanir; S.Yildiz; K.Ozturk; S.Celebi

    2013-01-01

    The magnetization of Gd diffused YBa2Cu3OT-x is measured by a vibrating sample magnetometer (VSM) at selected temperatures (5,25,50,77 K).The experimental results for the magnetization are analyzed in the critical state framework involving Kim-Anderson field dependence Jc(H) =Jc0/(1 + |H|/Ho)n of critical current density and equilibrium magnetization Meq.It is found that the inclusion of the equilibrium magnetization becomes more important at higher temperatures.At 77 K,the shape of the isothermal M-H hysteresis curve is governed by the equilibrium magnetization.Some superconducting parameters are determined by fitting the calculated curves to the experimental data.

  1. Coexistence of long-ranged magnetic order and superconductivity in the pnictide superconductor SmFeAsO1-xFx (x=0,0.15)

    Science.gov (United States)

    Ryan, D. H.; Cadogan, J. M.; Ritter, C.; Canepa, F.; Palenzona, A.; Putti, M.

    2009-12-01

    Powder neutron-diffraction measurements on both SmFeAsO and the fluorine-doped superconductor, SmFeAsO0.85F0.15 , show that the Sm sublattice orders magnetically. In both cases we observe a simple layered antiferromagnetic arrangement of the ˜0.5μB Sm moments. This provides direct evidence that long-ranged magnetic order of the samarium moments coexists with superconductivity in the SmFeAsO1-xFx system.

  2. Simulation of magnetization and levitation properties of arrays of ring-shaped type-II superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jun, E-mail: linxj8686@163.com; Huang, Chenguang; Yong, Huadong; Zhou, Youhe, E-mail: zhouyh@lzu.edu.cn

    2017-03-15

    Highlights: • A strong magnetic coupling appears if the gap between the superconducting rings is small. • The saturation magnetization of superconducting rings is related to the radial gap but independent of the vertical gap. • The array of rings in a non-uniform field experiences a levitation force, which increases with increasing height or thickness of the rings. - Abstract: This paper presents an analysis of the magnetic and mechanical properties of arrays of superconducting rings arranged in axial, radial, and matrix configurations under different magnetic fields. In terms of the Bean's critical state model and the minimum magnetic energy method, the dependences of the magnetization and levitation behaviors on the geometry, number, and gap of the superconducting rings are obtained. The results show that when the applied field is spatially uniform, the magnetic property of the superconducting array is associated with the gaps between the rings. For the case of small gaps, the entire array becomes not easy to be fully penetrated by the induced currents, and the magnetic field profiles of which are almost the same as ones in a single large ring. If the superconducting array is fully penetrated, its saturation magnetization value is affected by the radial interval and, however, is almost independent of the vertical separation. When the applied field produced by a cylindrical permanent magnet is nonuniform, the superconducting array will be subjected to a levitation force. The levitation force increases monotonically and finally reaches a saturation value with increasing height or thickness of the rings, and such saturation value is closely related to the inner radius of the array.

  3. Development of an experimental system for characterization of high-temperature superconductors cooled by liquid hydrogen under the external magnetic field

    Science.gov (United States)

    Tatsumoto, H.; Shirai, Y.; Shiotsu, M.; Naruo, Y.; Kobayashi, H.; Inatani, Y.

    2014-05-01

    An experimental system has been developed to investigate electro-magnetic properties of high-Tc superconductors cooled by liquid hydrogen under the external magnetic field of up to 7 T. A LH2 cryostat is concentrically mounted on the inside of a LHe cryostat to cool a NbTi superconducting magnet. The experimental system is installed in an explosion-proof room. Explosion proof electrical devices are used and current leads are covered with an enclosure filled with nitrogen gas. A remote control system has been developed. Furthermore, the effects of stray magnetic field on the existing and the new devices are investigated and electro-magnetic shielding panels and enclosure made of iron were designed. It is confirmed through the cryogenic test that the experimental system meets the design requirements.

  4. Manufacturing of Superconductors

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Bay, Niels

    Superconducting tapes based on the ceramic high temperature superconductor (HTS) is a new promising product for high current applications such as electro-magnets and current transmission cables. The tapes are made by the oxide powder in tube (OPIT) method implying drawing and rolling of silver tu...

  5. Growth anisotropy effect of bulk high temperature superconductors on the levitation performance in the applied magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, J., E-mail: jzheng@swjtu.edu.cn; Liao, X.L.; Jing, H.L.; Deng, Z.G.; Yen, F.; Wang, S.Y.; Wang, J.S.

    2013-10-15

    Highlights: • The single-layer bulk HTSC with AGSBP obtains better levitation performance than that of MGSBP. • The double-layer bulk with AGSBP obtains better levitation performance than that of MGSBP too. • The double-layer bulk finding is contrast to MGSBP if pursuing high trapped field. • The optimization is highlighted by simple and easy operation, thus economical in the practice. -- Abstract: Growth anisotropies of bulk high temperature superconductors (HTSCs) fabricated by a top-seeded melt texture growth process, that is, different pinning effect in the growth sectors (GSs) and growth sector boundaries (GSBs), possess effect on the macro flux trapping and levitation performance of bulk HTSCs. Previous work (Physics Procedia, 36 (2012) 1043) has found that the bulk HTSC array with aligned GSB pattern (AGSBP) exhibits better capability for levitation and suppression of levitation force decay above a permanent magnet guideway (PMG) compared with misaligned GSB pattern (MGSBP). In this paper, we further examine this growth anisotropy effect on the maglev performance of a double-layer bulk HTSC. In contrast to reported trapped flux cases (Supercond. Sci. Technol. 19 (2006) S466), the two superposed bulk HTSCs with same AGSBP with PMG are found to show better maglev performance. These series of results are helpful and support a new way for the performance optimization of present HTS maglev systems.

  6. Electro-magnetic properties and engineering applications of single-domain high temperature superconductor yttrium barium copper oxide

    Science.gov (United States)

    Qu, Dehui

    High temperature superconductors (HTS) exhibit a commonly known Meissner effect, which can cause a unusually strong magnetic repulsion. Using this effect, magnetic bearings have been constructed with 1000 times less friction than that of conventional bearings. The commercialization of the flywheel energy storage device (FESD) could mean cost-savings for the electric power industry. For instance, using a flywheel device, the energy can be generated most efficiently at a steady rate, and meet the high demand in peak daytime hours. Since the magnetic levitation using HTS involves very little friction, only about 0.1 percent of stored energy is lost per hour making electricity consumption most economic. As FESD is to be commercialized in the future, need for more expensive fossil fuel generating plants would be reduced or eliminated. In magnetic levitation using an anisotropic HTS such as YBa2Cu 3Ox, it has been reported that the levitation force is determined by sample geometry and flux pinning strength. Previous studies on critical current density and flux creep have indicated that crystal orientation should have a significant effect on levitation force due to superconducting anisotropy. The underline mechanisms governing the levitation force associated with superconducting anisotropy have not, however, been identified. Finding the crystal orientation dependence of the levitation force is not only of great interest to fundamental studies, but also important for industrial applications. For instance, the levitation force has been found to be one of the key parameters influencing the energy loss in flywheel energy storage. Enhancement of the levitation force has been the main goal in HTS materials development for magnetic bearings. The study of the relationship between levitation force and various materials parameters including crystal orientation, flux pinning strength, and geometry provide valuable information in further optimizing the materials performance in

  7. Superconductivity and magnetism in intermetallic Bi3Ni1-xFex superconductor

    Science.gov (United States)

    Gonsalves, Silvio Henrique; Opata, Yuri Aparecido; Pinheiro, Lincoln Brum Leite Gusmão; Da Silva Leal, Adriane Consuelo; Monteiro, João Frederico Haas Leandro; Siqueira, Ezequiel Costa; de Andrade, André Vitor Chaves; Jurelo, Alcione Roberto

    2016-09-01

    In this work, we investigated the apparent coexistence of superconductivity and magnetism in polycrystalline Bi3Ni1-xFex samples for low concentrations of iron (0 ≤ x ≤ 0.10). The compound was synthesized by the solid-state reaction method and characterized by X-ray diffraction and magnetic measurements. From X-ray, it was observed that the main phase corresponds to an orthorhombic structure with space group Pnma and shows no dependence on the Fe concentration. From magnetic measurements, it was observed that the critical temperature was not affected by iron doping and that ferromagnetism and superconductivity coexist apparently in an interesting interplay.

  8. Pressure Dependence of the Magnetization in the Ferromagnetic Superconductor UGe2

    Science.gov (United States)

    Pfleiderer, C.; Huxley, A. D.

    2002-09-01

    We report measurements of the pressure dependence of the low-temperature magnetization that show that the two pressure induced magnetic transitions in UGe2 are of first order. Further, the pressure dependence of the uniform susceptibility relative to the superconducting transition is not as expected if the latter is driven by the proximity to a ferromagnetic quantum critical point. Our data instead suggest that the superconducting pairing could be associated with a sharp spike in the electronic density of states that is also responsible for the lower pressure magnetic transition.

  9. On the Coexistence of Superconductivity and Magnetic Ordering in Unconventional Superconductors

    Science.gov (United States)

    Rodrigues de Campos, Fillipi Klos; Zanella, Fernando; Dartora, C. A.

    2017-04-01

    It is demonstrated that the coexistence of superconductivity and magnetic ordering, occurring, for instance, in iron-based pnictides and uranium compounds, is not forbidden by classical Maxwell's equations and London-type equations. It predicts simply that internal magnetization is allowed but localized magnetic moments are screened at distances of the order of the London penetration depth. A microscopic theory is considered for the case of ferromagnetic ordering, described in simple terms by electron-magnon coupling. For the sake of simplicity, we assume that itinerant electrons are not responsible for the magnetic ordering, but interact with phonon and magnon excitations, leading to an alternative Cooper pair channel. The temperature dependence and the isotope effect of the superconducting gap is also analysed.

  10. Alternating magnetic field losses in ATLAS type aluminium stabilized NbTi superconductors

    CERN Document Server

    Boxman, E W; ten Kate, H H J

    2002-01-01

    During ramping up- and down of the current in large-scale magnets the ramp losses are an important factor affecting the thermal and electro-magnetic stability of the system. The calculation of the losses is not straightforward due to the large dimensions of the conductor (~600 mm/sup 2/) implying that diffusion effects have to be taken into account. The AC-losses of the Al stabilized NbTi cable conductors used in the ATLAS magnet system were measured in 0.5 m long samples, using an inductive method with pick-up coils as well as the calorimetric method. External varying magnetic fields up to 2 tesla amplitude were applied parallel and perpendicular to the conductor wide surface. The results are compared to theory. It is found that hysteresis loss, eddy current loss in the Aluminum cladding and cable-to-cladding coupling loss contribute most to the AC loss. (5 refs).

  11. The magnetic and crystalline structure of the Laves phase superconductor CeRu{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Huxley, A.; Boucherle, J.X.; Bonnet, M.; Bourdarot, F.; Schustler, I.; Caplan, D. [CEA, Departement de Recherche Fondamental sur la Matiere Condensee, SPSMS, Grenoble 38054 (France); Lelievre, E.; Bernhoeft, N. [Institut Laue - Langevin, Grenoble (France); Lejay, P. [Centre de Recherche sur les Tres Basses Temperatures, CNRS, Grenoble (France); Gillon, B. [CEA, Laboratoire Leon Brillouin, Saclay (France)

    1997-05-19

    We report measurements of the field-induced magnetization density in CeRu{sub 2}. The main results of the study are that the magnetic density is located equally at the Ce and Ru sites, and that the distribution of the induced magnetization about the Ce site extends to larger distances than predicted for Ce{sup 3+} ions with well localized f electrons. Our measurements also cover the superconducting state, where we do not observe any suppression of the spin susceptibility. In an accompanying structural study (in zero field) of our single crystal we detect a small deviation from the ideal Laves phase structure. These results are discussed in relation to the unusual electronic and magnetic properties of this compound. (author)

  12. Effect of Doping and Pressure on Magnetism and Lattice Structure of Fe-Based Superconductors

    Science.gov (United States)

    2010-04-14

    large higher order terms in the Landau functional. I. INTRODUCTION The magnetic properties of the Fe-based superconduc- tors are believed to be the key...reflection of the magnetostrictive nature of Fe), and in terms of an orthorhombic distortion in the magnetically ordered state (it is nearly universally...physical mean- ing of this is clear: as discussed, the Fe ion is charac- terized by a large magnetostrictive effect; compressing the ion results in a

  13. Currents, magnetization and AC-losses of YBa 2Cu 3O 7 superconductors in rapidly changing magnetic fields

    Science.gov (United States)

    Kwasnitza, K.; Plotzner, V.; Waldmann, M.; Widmer, E.

    1988-06-01

    In YBa 2Cu 3O 7 samples of different shape time dependent magnetization currents were induced at 4.2K by the application of rapid magnetic field changes. This contactless method allows the study of the intergrain and intragrain currents in the resistive flux flow state.

  14. A Multifunctional Biomaterial with NIR Long Persistent Phosphorescence, Photothermal Response and Magnetism.

    Science.gov (United States)

    Wu, Yiling; Li, Yang; Qin, Xixi; Qiu, Jianrong

    2016-09-20

    There are many reports on long persistent phosphors (LPPs) applied in bioimaging. However, there are few reports on LPPs applied in photothermal therapy (PTT), and an integrated system with multiple functions of diagnosis and therapy. In this work, we fabricate effective multifunctional phosphors Zn3 Ga2 SnO8 : Cr(3+) , Nd(3+) , Gd(3+) with NIR persistent phosphorescence, photothermal response and magnetism. Such featured materials can act as NIR optical biolabels and magnetic resonance imaging (MRI) contrast agents for tracking the early cancer cells, but also as photothermal therapeutic agent for killing the cancer cells. This new multifunctional biomaterial is expected to open a new possibility of setting up an advanced imaging-guided therapy system featuring a high resolution for bioimaging and low side effects for the photothermal ablation of tumors.

  15. A persistent-mode 0.5 T solid-nitrogen-cooled MgB2 magnet for MRI

    Science.gov (United States)

    Ling, Jiayin; Voccio, John P.; Hahn, Seungyong; Qu, Timing; Bascuñán, Juan; Iwasa, Yukikazu

    2017-02-01

    This paper presents construction details and test results of a persistent-mode 0.5 T MgB2 magnet developed at the Francis Bitter Magnet Laboratory, MIT. The magnet, of 276 mm inner diameter and 290 mm outer diameter, consisted of a stack of eight solenoidal coils with a total height of 460 mm. Each coil was wound with monofilament MgB2 wire, equipped with a persistent-current switch and terminated with a superconducting joint, forming an individual superconducting loop. Resistive solder joints connected the eight coils in series. The magnet, after being integrated into a testing system, immersed in solid nitrogen, was operated in a temperature range of 10-13 K. A two-stage cryocooler was deployed to cool a radiation shield and the cold mass that included mainly ˜60 kg of solid nitrogen and the magnet. The solid nitrogen was capable of providing a uniform and stable cryogenic environment to the magnet. The magnet sustained a 0.47 T magnetic field at its center persistently in a range of 10-13 K. The current in each coil was inversely calculated from the measured field profile to determine the performance of each coil in persistent-mode operation. Persistent-current switches were successfully operated in solid nitrogen for ramping the magnet. They were also designed to absorb magnetic energy in a protection mechanism; its effectiveness was evaluated in an induced quench.

  16. Gadolinium oxysulfide nanoprobes with both persistent luminescent and magnetic properties for multimodal imaging

    OpenAIRE

    ROSTICHER, C.; Viana, Bruno; Fortin, M.-A.; Lagueux, J.; Faucher, L; Chanéac, Corinne

    2016-01-01

    International audience; Persistent luminescence and magnetic properties of Gd2O2S: Eu 3+ , Ti 4+ , Mg 2+ nanoparticles have been studied to attest the relevance of such nanoparticles as nanoprobes for multimodal imaging. The development of new imaging tools is required to improve the quality of medical images and then to diagnose some disorders as quickly as possible in order to ensure more effective treatment. Multimodal imaging agents here developed combine the high resolution abilities of ...

  17. Electronic and magnetic phase diagram of superconductors, SmFeAsO1-xFx

    Science.gov (United States)

    Kamihara, Yoichi; Nomura, Takatoshi; Hirano, Masahiro; Kim, Jung Eun; Kato, Kenichi; Takata, Masaki; Kobayashi, Yasuhiro; Kitao, Shinji; Higashitaniguchi, Satoshi; Yoda, Yoshitaka; Seto, Makoto; Hosono, Hideo

    2010-03-01

    A crystallographic and magnetic phase diagram of SmFeAsO1-xFx is determined as a function of x in terms of temperature based on electrical transport and magnetization, synchrotron powder x-ray diffraction, 57Fe Mössbauer spectra (MS), and 149Sm nuclear resonant forward scattering (NRFS) measurements. MS revealed that the magnetic moments of Fe were aligned antiferromagnetically at ~144 K (TN(Fe)). The magnetic moment of Fe (MFe) is estimated to be 0.34 μB/Fe at 4.2 K for undoped SmFeAsO; MFe is quenched in superconducting F-doped SmFeAsO. 149Sm NRFS spectra revealed that the magnetic moments of Sm start to order antiferromagnetically at 5.6 K (undoped) and 4.4 K (TN(Sm)) (x=0.069). Results clearly indicate that the antiferromagnetic (AF) Sm sublattice coexists with the superconducting phase in SmFeAsO1-xFx below TN(Sm), while the AF Fe sublattice does not coexist with the superconducting phase.

  18. Vibrational Properties of High- Superconductors Levitated Above a Bipolar Permanent Magnetic Guideway

    Science.gov (United States)

    Liu, Lu; Wang, Jiasu

    2014-05-01

    A bipolar permanent magnetic guideway (PMG) has a unique magnetic field distribution profile which may introduce a better levitation performance and stability to the high- superconducting (HTS) maglev system. The dynamic vibration properties of multiple YBCO bulks arranged into different arrays positioned above a bipolar PMG and free to levitate were investigated. The acceleration and resonance frequencies were experimentally measured, and the stiffness and damping coefficients were evaluated for dynamic stability. Results indicate that the levitation stiffness is closely related to the field-cooling-height and sample positioning. The damping ratio was found to be low and nonlinear for the Halbach bipolar HTS-PMG system.

  19. 373 K Superconductors

    CERN Document Server

    Kostadinov, Ivan Zahariev

    2016-01-01

    Experimental evidence of superconductors with critical temperatures above $373\\:K$ is presented. In a family of different compounds we demonstrate the superconductor state, the transition to normal state above $387\\:K$, an intermediate $242\\:K$ superconductor, susceptibility up to $350\\:K$, $I-V$ curves at $4.2\\:K$ in magnetic field of $12\\:T$ and current up to $60\\:A$, $300\\:K$ Josephson Junctions and Shapiro steps with radiation of $5\\:GHz$ to $21\\:THz$, $300\\:K$ tapes tests with high currents up to $3000\\:A$ and many $THz$ images of coins and washers. Due to a pending patent, the exact chemical characterization and technological processes for these materials are temporarily withheld and will be presented elsewhere.

  20. Lightning in superconductors.

    Science.gov (United States)

    Vestgården, J I; Shantsev, D V; Galperin, Y M; Johansen, T H

    2012-01-01

    Crucially important for application of type-II superconductor films is the stability of the vortex matter--magnetic flux lines penetrating the material. If some vortices get detached from pinning centres, the energy dissipated by their motion will facilitate further depinning, and may trigger a massive electromagnetic breakdown. Up to now, the time-resolved behaviour of these ultra-fast events was essentially unknown. We report numerical simulation results revealing the detailed dynamics during breakdown as within nanoseconds it develops branching structures in the electromagnetic fields and temperature, with striking resemblance of atmospheric lightning. During a dendritic avalanche the superconductor is locally heated above its critical temperature, while electrical fields rise to several kV/m as the front propagates at instant speeds near up to 100 km/s. The numerical approach provides an efficient framework for understanding the ultra-fast coupled non-local dynamics of electromagnetic fields and dissipation in superconductor films.

  1. Copper-tuned magnetic order and excitations in iron-based superconductors Fe1+yTe1-xSex

    Science.gov (United States)

    Wen, Jinsheng; Xu, Zhijun; Xu, Guangyong; Lumsden, Mark; Matsuda, Masaaki; Valdivia, Patrick; Bourret, Edith; Lee, Dunghai; Gu, Genda; Tranquada, John; Birgeneau, Robert

    2012-02-01

    We report neutron scattering results on the Cu-substitution effects in the iron-based superconductors, Fe1+yTe1-xSex. In the parent compound, it is found that Cu drives the low-temperature magnetic ground state from long-range commensurate antiferromagnetic order in Fe1.06TeCu0.04 to short-range incommensurate order in FeTeCu0.1. In the former sample, the structural and magnetic ordering temperature is 40 K; in FeTeCu0.1, the structural phase transition is not obvious and a transition to the spin-glass state is found at 22 K. Cu suppresses superconductivity in FeTe0.5Se0.5---Tc is reduced to 7 K with a 2% Cu doping, and no superconductivity is found in the 10% Cu-doped sample. In the meantime, the intensity and energy of the resonance mode are suppressed in the 2% Cu-doped sample, while there is no resonance in the non-superconducting sample. Besides, the low-temperature magnetic excitation spectra are distinct for these two samples, with the superconducting one having an ``hour-glass" shape and the other one having a ``waterfall" shape. Our results provide further insights on the interplay between magnetism and superconductivity in the iron-based superconductors.

  2. Protection of a test magnet wound with a Ag/BSCCO high-temperature superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Dresner, L.

    1992-10-01

    The properties of Ag/BSCCO conductor are studied and used to evaluate the feasibility of detecting normal zones in the conductor before the hot-spot temperature reaches critical levels. The results are applied to the protection of a 5-kJ test magnet.

  3. Application of Nb3Sn superconductors in high-field accelerator magnets

    NARCIS (Netherlands)

    Ouden, den Andries; Wessel, Sander; Krooshoop, Erik; Kate, ten Herman

    1997-01-01

    Last year a record central field of 11 T at first excitation at 4.4 K has been achieved with the experimental LHC model dipole magnet MSUT by utilising a high Jc powder-in-tube Nb3Sn conductor. This is the first real breakthrough towards fields well above 10 T at 4 K. The clear influence of magnetis

  4. Phonon-induced quadrupolar ordering of the magnetic superconductor TmNi2B2C

    DEFF Research Database (Denmark)

    Andersen, N.H.; Jensen, J.; Jensen, T.B.S.

    2006-01-01

    We present synchrotron x-ray diffraction studies revealing that the lattice of thulium borocarbide is distorted below T(Q)similar or equal to 13.5 K at zero field. T-Q increases and the amplitude of the displacements is drastically enhanced by a factor of 10 at 60 kOe when a magnetic field is app...

  5. Melt processed high-temperature superconductors

    CERN Document Server

    1993-01-01

    The achievement of large critical currents is critical to the applications of high-temperature superconductors. Recent developments have shown that melt processing is suitable for producing high J c oxide superconductors. Using magnetic forces between such high J c oxide superconductors and magnets, a person could be levitated.This book has grown largely out of research works on melt processing of high-temperature superconductors conducted at ISTEC Superconductivity Research Laboratory. The chapters build on melt processing, microstructural characterization, fundamentals of flux pinning, criti

  6. Non-Universal temperature dependencies of the low frequency ac magnetic susceptibility in high Tc superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Di Gioacchino, D.; Celani, F.; Tripodi, P. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Testa, A.M. [Consiglio Nazionale per le Ricerche, Monterotondo, RM, (Italy). Istituto di Chimica dei Materiali; Pace, S. [INFM, Univ. Salerno, Salerno (Italy). Dept. of Physics

    1999-07-01

    The paper is organized as follows. In Sec. 2 the non-linear diffusion problem is formulated in terms of a partial differential equation, together with the parallel resistor model for the 1-5 characteristics. To study in some detail the effects of thermally activated processes in different cases, we have chosen different temperature functional dependencies for the pinning potential, U{sub p}(T), and the critical current density, J{sub c}(T), related to particular pinning models. Local magnetic field profiles, magnetization cycles and {chi}n (T) are discussed in Sec. 3. Moreover, a comparison of numerical results with available experimental data and analytical approximated predictions is also presented. Finally, Sec. 4 is devoted to summary and conclusions.

  7. Vortex cutting in superconductors

    Science.gov (United States)

    Glatz, A.; Vlasko-Vlasov, V. K.; Kwok, W. K.; Crabtree, G. W.

    2016-08-01

    Vortex cutting and reconnection is an intriguing and still-unsolved problem central to many areas of classical and quantum physics, including hydrodynamics, astrophysics, and superconductivity. Here, we describe a comprehensive investigation of the crossing of magnetic vortices in superconductors using time dependent Ginsburg-Landau modeling. Within a macroscopic volume, we simulate initial magnetization of an anisotropic high temperature superconductor followed by subsequent remagnetization with perpendicular magnetic fields, creating the crossing of the initial and newly generated vortices. The time resolved evolution of vortex lines as they approach each other, contort, locally conjoin, and detach, elucidates the fine details of the vortex-crossing scenario under practical situations with many interacting vortices in the presence of weak pinning. Our simulations also reveal left-handed helical vortex instabilities that accompany the remagnetization process and participate in the vortex crossing events.

  8. Magnetic properties of fluorinated Pb-doped Hg-1223 high Tc superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hamdan, N.M.; Sastry, P.V.P.S.S.; Schwartz, J.

    2001-09-23

    Fluorination of Pb-doped HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (Hg-1223) system was investigated. Structural and magnetic measurements reveal that fluorine addition promotes the phase formation, optimize the charge carrier concentration, and enhance flux pinning. We report an increase in both the transition temperature and the critical current density through controlled fluorine incorporation. Even a possible change in the pinning mechanism in this technologically important system is suggested.

  9. Modeling of hysteretic behavior of the levitation force between superconductor and permanent magnet

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xing-da, E-mail: shuxdw@gmail.com [School of Information Engineering, Guangdong Medical College, No. 2, Eastern Wenming Road, Zhanjiang 524023 (China); Xu, Ke-Xi, E-mail: kxxu@staff.shu.edu.cn [Department of Physics, Shanghai University, Shanghai 200444 (China); Cao, Yue; Hu, Shun-bo; Zuo, Peng-xiang; Li, Guan-dong [Department of Physics, Shanghai University, Shanghai 200444 (China)

    2013-03-15

    Highlights: ► Experimental results on hysteretic behavior of the levitaion force are presented. ► Hysteresis loop for the first descent/ascent cycle of magnet is largest. ► Hysteresis loop for the second and subsequent cycles almost overlap each other. ► Yang’s frozen-image model cannot describe this characteristic of levitation force. ► An updated frozen-image model is developed to describe these experimental results. -- Abstract: The hysteretic behavior of the levitation force between a permanent magnet and a melt-textured-growth YBCO bulk has been investigated under both zero-field cooling (ZFC) and field cooling (FC) processes. It is found that both in ZFC and FC measurements, the hysteresis loop for the first descent/ascent cycle of magnet is relatively larger than that for the second or third cycle, and the hysteresis loops for Cycle 2–4 have the same area. These results can be qualitatively understood in terms of the critical state model. To describe these experimental results, we develop an updated frozen-image model, which is obtained by modifying the change rules of the vertical movement image in the advanced frozen-image model proposed by Yang et al. Comparing with the advanced frozen-image model proposed by Yang et al., our model cannot only give the hysteretic characteristic in the first descent–ascent cycle of magnet, but also show the hysteresis loops with the same area for the second and subsequent cycles.

  10. Modeling of hysteretic behavior of the levitation force between superconductor and permanent magnet

    Science.gov (United States)

    Wu, Xing-da; Xu, Ke-Xi; Cao, Yue; Hu, Shun-bo; Zuo, Peng-xiang; Li, Guan-dong

    2013-03-01

    The hysteretic behavior of the levitation force between a permanent magnet and a melt-textured-growth YBCO bulk has been investigated under both zero-field cooling (ZFC) and field cooling (FC) processes. It is found that both in ZFC and FC measurements, the hysteresis loop for the first descent/ascent cycle of magnet is relatively larger than that for the second or third cycle, and the hysteresis loops for Cycle 2-4 have the same area. These results can be qualitatively understood in terms of the critical state model. To describe these experimental results, we develop an updated frozen-image model, which is obtained by modifying the change rules of the vertical movement image in the advanced frozen-image model proposed by Yang et al. Comparing with the advanced frozen-image model proposed by Yang et al., our model cannot only give the hysteretic characteristic in the first descent-ascent cycle of magnet, but also show the hysteresis loops with the same area for the second and subsequent cycles.

  11. Phase transition of a heavy-fermion superconductor in a high magnetic field: Entanglement analysis

    Science.gov (United States)

    Afzali, R.; Ebrahimian, N.

    2013-08-01

    When the magnetic field is only acting on the spin of electrons, a transition from a normal to a modulated superconducting state or Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state may occur at low temperatures. A FFLO superconducting state, which accompanies an order parameter that oscillates spatially, may be stabilized by a high applied magnetic field or a molecular field. Quantum multipartite entanglement is a new procedure for investigating quantum phase transitions. In this article, we deal with the phase transition of the FFLO state of CeCoIn5 to a normal state by obtaining quantum multipartite entanglement of the system. For this purpose, using normal and anomalous Green functions and the density matrix, we obtain concurrence, as a measure of bipartite entanglement. Then, the order parameter and the magnetic -field dependence of multipartite entanglement in momentum space is calculated. The phase transition is determined, and the behavior of the system based on order parameter is discussed. Furthermore, the phase transitions of both the Bardeen-Cooper-Schrieffer (BCS) and FFLO states to the normal state are compared.

  12. Polarized neutron imaging and three-dimensional calculation of magnetic flux trapping in bulk of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Treimer, Wolfgang; Ebrahimi, Omid; Karakas, Nursel; Prozorov, Ruslan

    2012-05-17

    Polarized neutron radiography was used to study the three-dimensional magnetic flux distribution inside of single-crystal and polycrystalline Pb cylinders with large (cm3) volume and virtually zero demagnetization. Experiments with single crystals being in the Meissner phase (Tmagnetic field. 99.9999 wt % pure polycrystalline samples were exposed to the same homogeneous magnetic field (6.4 mT) and only a portion of the applied field was expelled. The trapped field in the sample (T

  13. Current-carrying element based on second-generation high-temperature superconductor for the magnet system of a fusion neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, M. S., E-mail: mihailnovikov@yandex.ru; Ivanov, D. P., E-mail: Ivanov-DP@nrcki.ru, E-mail: denis.ivanov30@mail.ru; Novikov, S. I., E-mail: novikov-si@nrcki.ru; Shuvaev, S. A., E-mail: ser-shuvaev@yandex.ru, E-mail: sergey.shuvaev@phystech.edu [National Research Center Kurchatov Institute (Russian Federation)

    2015-12-15

    Application of current-carrying elements (CCEs) made of second-generation high-temperature superconductor (2G HTS) in magnet systems of a fusion neutron source (FNS) and other fusion devices will allow their magnetic field and thermodynamic stability to be increased substantially in comparison with those of low-temperature superconductor (LTS) magnets. For a toroidal magnet of the FNS, a design of a helical (partially transposed) CCE made of 2G HTS is under development with forced-flow cooling by helium gas, a current of 20–30 kA, an operating temperature of 10–20 K, and a magnetic field on the winding of 12–15 T (prospectively ∼20 T). Short-sized samples of the helical flexible heavy-current CCE are being fabricated and investigated; a pilot-line unit for production of long-sized CCE pieces is under construction. The applied fabrication technique allows the CCE to be produced which combines a high operating current, thermal and mechanical stability, manufacturability, and low losses in the alternating modes. The possibility of fabricating the CCE with the outer dimensions and values of the operating parameter required for the FNS (and with a significant margin) using already available serial 2G HTS tapes is substantiated. The maximum field of toroidal magnets with CCEs made of 2G HTS will be limited only by mechanical properties of the magnet’s casing and structure, while the thermal stability will be approximately two orders of magnitude higher than that of toroidal magnets with LTS-based CCEs. The helical CCE made of 2G HTS is very promising for fusion and hybrid electric power plants, and its design and technologies of production, as well as the prototype coils made of it for the FNS and other tokamaks, are worth developing now.

  14. Spin manipulation in nanoscale superconductors.

    Science.gov (United States)

    Beckmann, D

    2016-04-27

    The interplay of superconductivity and magnetism in nanoscale structures has attracted considerable attention in recent years due to the exciting new physics created by the competition of these antagonistic ordering phenomena, and the prospect of exploiting this competition for superconducting spintronics devices. While much of the attention is focused on spin-polarized supercurrents created by the triplet proximity effect, the recent discovery of long range quasiparticle spin transport in high-field superconductors has rekindled interest in spin-dependent nonequilibrium properties of superconductors. In this review, the experimental situation on nonequilibrium spin injection into superconductors is discussed, and open questions and possible future directions of the field are outlined.

  15. Cable-in-conduit superconductors for fusion magnets: electro-magnetic modelling for understanding and optimizing their transport properties

    NARCIS (Netherlands)

    Rolando, Gabriella

    2013-01-01

    Cable-In-Conduit conductors feature large current-carrying capacity and stability against local and transient heat deposition. As such they are suitable for application in superconducting magnets for nuclear fusion, as the ones of the International Thermonuclear Experimental Reactor (ITER). Due to

  16. Cable-in-conduit superconductors for fusion magnets: electro-magnetic modelling for understanding and optimizing their transport properties

    NARCIS (Netherlands)

    Rolando, G.

    2013-01-01

    Cable-In-Conduit conductors feature large current-carrying capacity and stability against local and transient heat deposition. As such they are suitable for application in superconducting magnets for nuclear fusion, as the ones of the International Thermonuclear Experimental Reactor (ITER). Due to t

  17. Variation in energy stored and dissipated in type-II superconductor in applied ac magnetic field with relative phase of two sinusoidal components of the field

    Science.gov (United States)

    Janů, Zdeněk; Chagovets, Tymofiy

    2017-01-01

    We show that both the energy stored and dissipated by a system with hysteretic nonlinearity in an applied field varies with the relative phase of the sinusoidal components of the field, even if the magnitude of these components, and thus an effective value of the field, are kept constant. The explored system is a type-II superconductor in the critical state subjected to a time varying applied magnetic field. Complete analytical expressions for hysteresis loops, determined from basic physical phenomena, are known for this system. A theoretically predicted variation in the energy is in good agreement with our experimental measurements.

  18. Surface critical magnetic field c3() of a bulk superconductor MgB2 using two-band Ginzburg–Landau theory

    Indian Academy of Sciences (India)

    I N Askerzade

    2003-09-01

    Two-band Ginzburg–Landau (TB G–L) equations for a bulk MgB2 were solved analytically to determine the temperature dependence of surface critical magnetic field Hc3(). It is shown that c3() has the same temperature dependence with c2(), similar to the case of a single-band superconductor, c3()=1.66 c2(). We use an elimination procedure for the decoupling of G–L equations of two-band superconductivity, which eases the calculations. It is expected that the temperature dependence for c3() gives positive curvature near c.

  19. NMR Studies of the Candidate Topological Superconductor Sn1-xInxTe: Spin-Triplet Superconductivity Robust against Magnetic Impurities

    Science.gov (United States)

    Lu, X. R.; Ma, L.; Dai, J.; Wang, P.; Normand, B.; Yu, W.; Zhong, R. D.; Schneeloch, J.; Xu, Z. J.; Gu, G. D.

    2013-03-01

    In-doped SnTe is a low-carrier-density semiconductor with strong spin-orbit coupling, and has been proposed to be a topological superconductor. We report nuclear magnetic resonance (NMR) studies of both 119Sn and 125Te nuclei, performed on single crystals of Sn1-xInxTe, where Tc = 1 . 8 K for x = 0 . 1 . Under an applied field of 0.33 T, the spin-lattice relaxation rate 1/119T1 drops rapidly below 1.2 K, indicating bulk superconductivity. We observe absolutely no change in the Knight shift with temperature when T magnetic impurity effects. Thus the fact that Tc in our samples is insensitive to the sample purity suggests that superconductivity in Sn1-xInxTe is robust against magnetic impurities, in contrast to the situation in conventional superconductors.

  20. Robustness of s-wave pairing symmetry in iron-based superconductors and its implications for fundamentals of magnetically driven high-temperature superconductivity

    Science.gov (United States)

    Hu, Jiangping; Yuan, Jing

    2016-10-01

    Based on the assumption that the superconducting state belongs to a single irreducible representation of lattice symmetry, we propose that the pairing symmetry in all measured iron-based superconductors is generally consistent with the A 1 g s-wave. Robust s-wave pairing throughout the different families of iron-based superconductors at different doping regions signals two fundamental principles behind high- T c superconducting mechanisms: (i) the correspondence principle: the short-range magnetic-exchange interactions and the Fermi surfaces act collaboratively to achieve high- T c superconductivity and determine pairing symmetries; (ii) the magnetic-selection pairing rule: superconductivity is only induced by the magnetic-exchange couplings from the super-exchange mechanism through cation-anion-cation chemical bonding. These principles explain why unconventional high- T c superconductivity appears to be such a rare but robust phenomena, with its strict requirements regarding the electronic environment. The results will help us to identify new electronic structures that can support high- T c superconductivity.

  1. Magnetism in the iron-based superconductors: The determination of spin-nematic fluctuations as the primary order parameter and its implications for unconventional superconductivity

    Science.gov (United States)

    Taddei, Keith M.

    With nearly innumerable applications, superconductivity stands as a holy grail in the research of quantum phenomena. Understanding the mechanism that begets the fabled pairing of electrons which leads to zero resistance is the most significant undertaking in order to bring to fruition all of superconductivity's splendor. Yet the interaction which couples electrons in the most promising family of superconductors known as unconventional superconductors, which show the highest Tc's and largest upper critical fields remains a mystery. Intense study over the past several decades on the cuprate superconductors has allowed for the identification of several candidate mechanisms --- cardinal of which is magnetic fluctuations --- however as of yet the question still remains. Recently, the discovery of the iron-based superconductors has provided another fruitful avenue through which this mechanism can be probed. Excitingly in these materials superconductivity not only arises near a magnetic instability - a situation which is expected to be particularly suited for engendering superconductivity should magnetic fluctuations be the pairing mechanism - but also exhibit the microscopic co-existence of the two presumably adversarial phenomena. In the work presented here the powerful techniques of neutron and x-ray diffraction will be used to study two particularly interesting members of this family: the intercalated iron-selenide CsxFe 2--xSe2 and two members of the iron-arsenide 122 family (BaFe2(As1--xPx)2 and Sr1--xNaxFe2As 2). Though isostructural at high temperatures, these two materials behave remarkably differently and the idiosyncratic manifestations of superconductivity and ordered magnetism in either give clues as to how the latter might stabilize the former. The iron-selenides will be shown to exhibit a complex phase space with phase separation leading to stabilization of magnetism and superconductivity in separate phases. The structure, behavior and complex vacancy

  2. Measurement of the magnetic induction vector in superconductors using a double-layer Hall sensor array

    Science.gov (United States)

    Abulafia, Y.; McElfresh, M.; Shaulov, A.; Yeshurun, Y.; Paltiel, Y.; Majer, D.; Shtrikman, H.; Zeldov, E.

    1998-06-01

    We describe an experimental technique for simultaneous measurement of both the normal (Bz) and the in-plane (Bx) components of the magnetic induction field near the surface of a superconducting sample. This technique utilizes a novel design of a double-layered Hall sensor array fabricated from a GaAs/AlGaAs heterostructure containing two parallel layers of a two-dimensional electron gas. The effectiveness of this technique is demonstrated in measurements of Bx and Bz and the current distribution at the surface of a thin YBa2Cu3O7 crystal.

  3. Method for improving performance of high temperature superconductors within a magnetic field

    Science.gov (United States)

    Wang, Haiyan; Foltyn, Stephen R.; Maiorov, Boris A.; Civale, Leonardo

    2010-01-05

    The present invention provides articles including a base substrate including a layer of an oriented cubic oxide material having a rock-salt-like structure layer thereon; and, a buffer layer upon the oriented cubic oxide material having a rock-salt-like structure layer, the buffer layer having an outwardly facing surface with a surface morphology including particulate outgrowths of from 10 nm to 500 run in size at the surface, such particulate outgrowths serving as flux pinning centers whereby the article maintains higher performance within magnetic fields than similar articles without the necessary density of such outgrowths.

  4. Superconductor and cable R&D for high field accelerator magnets at Fermilab

    CERN Document Server

    Barzi, E; Andreev, N; Bauer, P; Chichili, D R; Fratini, M; Elementi, L; Hoffman, J; Limon, P J; Mattafirri, S; Rey, J M; Yamada, R; Zlobin, A V

    2002-01-01

    This paper presents past results and future goals of the Nb/sub 3/Sn strand and cable R&D being performed within the High Field Magnet program at Fermilab. Research tools include a reaction site for Nb /sub 3/Sn, a Short Sample Test Facility, a Scanning Electron Microscope, and a 28-strand cabling machine. Strands of various designs and diameters produced with the Internal Tin, Modified Jelly Roll, and Powder-in-Tube methods, and several Rutherford-type cables were studied. (18 refs).

  5. Scaling between magnetic field and temperature in the high-temperature superconductor BaFe2(As1-xPx)2

    Science.gov (United States)

    Hayes, Ian M.; McDonald, Ross D.; Breznay, Nicholas P.; Helm, Toni; Moll, Philip J. W.; Wartenbe, Mark; Shekhter, Arkady; Analytis, James G.

    2016-10-01

    Many exotic metallic systems have a resistivity that varies linearly with temperature, and the physics behind this is thought to be connected to high-temperature superconductivity in the cuprates and iron pnictides. Although this phenomenon has attracted considerable attention, it is unclear how the relevant physics manifests in other transport properties, for example their response to an applied magnetic field. We report measurements of the high-field magnetoresistance of the iron pnictide superconductor BaFe2(As1-xPx)2 and find that it obeys an unusual scaling relationship between applied magnetic field and temperature, with a conversion factor given simply by the ratio of the Bohr magneton and the Boltzmann constant. This suggests that magnetic fields probe the same physics that gives rise to the T-linear resistivity, providing a new experimental clue to this long-standing puzzle.

  6. Magnetization measurements of non-centrosymmetric superconductor LaPt3Si: Construction of low temperature magnetometers with the SQUID and Hall sensor

    Science.gov (United States)

    Fujisawa, Takumi; Yamaguchi, Akira; Motoyama, Gaku; Kawakatsu, Daichi; Sumiyama, Akihiko; Takeuchi, Tetsuya; Settai, Rikio; Ōnuki, Yoshichika

    2015-04-01

    We report magnetization of a non-centrosymmetric superconductor, LaPt3Si below 0.6 K up to 200 Oe. The home-made SQUID and Hall sensor magnetometers that operate below 1 K were constructed for this purpose. Although the SQUID magnetometer is more sensitive than the Hall sensor’s one, it was found not to work correctly for the rapid magnetization change of LaPt3Si below 0.4 K. The Hall sensor magnetometer, in contrast, can properly detect magnetization jumps in the M-H curve of the superconducting state. The observed flux jumps are probably related to the interfusion of the mixed state of the LaPt3Si that is observed in the μSR measurements.

  7. Two-dimensional orbital-like magnetic order in the high-temperature La(2-x)Sr(x)CuO4 superconductor.

    Science.gov (United States)

    Balédent, V; Fauqué, B; Sidis, Y; Christensen, N B; Pailhès, S; Conder, K; Pomjakushina, E; Mesot, J; Bourges, P

    2010-07-09

    In high-temperature copper oxide superconductors, a novel magnetic order associated with the pseudogap phase has been identified in two different cuprate families over a wide region of temperature and doping. We report here the observation below 120 K of a similar magnetic ordering in the archetypal cuprate La(2-x)Sr(x)CuO4 (LSCO) system for x=0.085. In contrast with the previous reports, the magnetic ordering in LSCO is only short range with an in-plane correlation length of ∼10  A and is bidimensional (2D). Such a less pronounced order suggests an interaction with other electronic instabilities. In particular, LSCO also exhibits a strong tendency towards stripes ordering at the expense of the superconducting state.

  8. Contrast-enhanced magnetic resonance angiography of persistent fifth aortic arch in children

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Yumin; Zhu, Ming; Sun, Aimin; Li, Yuhua [Shanghai Jiao Tong University School of Medicine, Department of Radiology, Shanghai Children' s Medical Center, Shanghai (China); Jaffe, Richard B. [Primary Children' s Medical Center, Department of Medical Imaging, Salt Lake City, UT (United States); Gao, Wei [Shanghai Jiao Tong University School of Medicine, Department of Cardiology, Shanghai Children' s Medical Center, Shanghai (China)

    2007-03-15

    Cine angiography and echocardiography have been utilized to diagnose congenital aortic arch anomalies. However, the visualization of great vessels by echocardiography is limited, while cine angiography requires cardiac catheterization with ionizing radiation. Contrast-enhanced magnetic resonance angiography (MRA) is a noninvasive modality suitable for visualization of congenital aortic arch anomalies. To evaluate the utility of contrast-enhanced MRA in the diagnosis of persistent fifth aortic arch, a rare congenital aortic arch anomaly, and to compare the diagnostic accuracy of MRA with that of echocardiography and cine angiography. In four pediatric patients, contrast-enhanced MRA studies were performed for diagnosing persistent fifth aortic arch. The findings of MRA were compared with echocardiographic findings and confirmed by cine angiography and operation. Transthoracic surface echocardiography noted an aberrant vessel arising from the ascending aorta in two of four patients; the etiology of this vessel was uncertain. In the other two patients a diagnosis of coarctation was made. Of the four patients, only one was diagnosed with interruption of the aortic arch. Contrast-enhanced MRA clarified uncertain echocardiographic findings, enabling the correct diagnosis of persistent fifth aortic arch with fourth aortic arch interruption in all four patients. Contrast-enhanced MRA is a safe, accurate, and fast imaging technique for the evaluation of persistent fifth aortic arch and may obviate the need for conventional cine angiography. Cardiac catheterization may be reserved for some types of complicated congenital heart disease and for obtaining hemodynamic information. (orig.)

  9. Estimation of the Required Amount of Superconductors for High-field Accelerator Dipole Magnets

    CERN Document Server

    Schwerg, N

    2007-01-01

    The coil size and the corresponding amount of superconducting material that is used during the design process of a magnet cross-section have direct impacts on the overall magnet cost. It is therefore of interest to estimate the minimum amount of conductors needed to reach the defined field strength before a detailed design process starts. Equally, it is useful to evaluate the efficiency of a given design by calculating the amount of superconducting cables that are used to reach the envisaged main field by simple rule. To this purpose, the minimum amount of conductors for the construction of a dipole of given main field strength and aperture size is estimated taking the actual critical current density of the used strands into account. Characteristic curves applicable for the NED Nb3Sn strand specification are given and some of the recently studied different dipole configurations are compared. Based on these results, it is shown how the required amount of conductors changes due to the iron yoke contribution and...

  10. Magnetic field dependent microwave absorption studies on a MgB{sub 2} superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Bhide, M.K.; Kadam, R.M.; Sastry, M.D. [Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Singh, Ajay; Sen, Shashwati; Aswal, D.K.; Sahni, V.C.; Gupta, S.K. [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India)]. E-mail: drgupta@magnum.barc.ernet.in

    2001-08-01

    Polycrystalline MgB{sub 2}, synthesized using a conventional solid-state reaction route, has been investigated for its magnetic field dependent microwave absorption using a standard X-band EPR spectrometer. The changes in microwave absorption as a function of temperature and/or magnetic field were recorded by following the microwave reflectivity of a sample-loaded cavity. The modulated low-field microwave absorption signal was found to be similar to that observed in high-temperature superconducting materials. The field dependent direct microwave absorption in the 0-10 kG range was used to determine H{sub c1} values at different temperatures, and the value of H{sub c1}(0) was found to be 250 G. The absorbed microwave power has been found to obey a (H){sup 1/2} dependence with a change of slope indicating a transition from a strongly pinned flux lattice to the flux flow regime. (author)

  11. Magnetic relaxation measurements of a high-T{sub c} oxide superconductor using microwave absorption

    Energy Technology Data Exchange (ETDEWEB)

    Noujima, Masafumi; Shiiyama, Kenichi; Kinoshita, Chiken [Kyushu Univ., Fukuoka (Japan)

    1998-09-01

    The pinning potential of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} with and without electron irradiation has been determined. Single crystals of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} were irradiated with 1 MeV electrons at room temperature in a high voltage electron microscope. Magnetic relaxation of the non-irradiated and irradiated crystals was measured with use of a microwave absorption method at T=79 K and magnetic fields, H = 0 - 0.13 T. The relaxation process was described in terms of the pinning potential and its anisotropy to get the following conclusions. (1) The pinning potential of the irradiated crystal is 2.2 times higher than that of the virgin crystal. (2) Isolated point defects, such as vacancies and interstitials provide good pinning centers. (3) The point defects produced by the electron irradiation make the pinning potential anisotropic. (author)

  12. Study of some superconducting and magnetic materials on high T sub c oxide superconductors

    Science.gov (United States)

    Wu, M. K.

    1987-01-01

    On the basis of existing data it appears that the high-temperature superconductivity above 77 K reported here, occurs only in compound systems consisting of a phase other than the K2NiF4 phase. A narrow superconducting transition was obtained with T sub c0 = 98 K and T sub c1 = 94 K in Y-Ba-Cu-O (YBCO). Preliminary results indicate that YBCO is rather different from the layered LaBCO, LaSCO, and LaCCO. While electron-photon interaction cannot be absent from this compound system, nonconventional enhanced superconducting interactions due to interfaces, Resonating Valence Bond (RVB) states, or even a superconducting state beyond the BCS framework, may be required to account for the high T sub c in YBCO. It is believed that study of the possible subtle correlation between magnetism and superconductivity will definitely provide important insight into the superconducting mechanism in YBCO and other oxides.

  13. Magnetic-field-induced superconductor-metal-insulator transitions in bismuth metal graphite

    Science.gov (United States)

    Suzuki, Masatsugu; Suzuki, Itsuko S.; Lee, Robert; Walter, Jürgen

    2002-07-01

    Bismuth metal graphite (MG) has a unique layered structure where Bi nanoparticles are encapsulated between adjacent sheets of nanographites. The superconductivity below Tc (=2.48 K) is due to Bi nanoparticles. The Curie-like susceptibility below 30 K is due to conduction electrons localized near zigzag edges of nanographites. A magnetic-field-induced transition from metallic to semiconductorlike phase is observed in the in-plane resistivity ρa around Hc (~25 kOe) for both H⊥c and H||c (c: c axis). A negative magnetoresistance in ρa for H⊥c (040 kOe) suggest the occurrence of a two-dimensional weak-localization effect.

  14. Electron beam welding of copper-stabilized superconductors for a large bubble chamber magnet

    CERN Document Server

    Albrecht, C

    1972-01-01

    In the European Nuclear Research Center CERN in Geneva, the presently largest hydrogen bubble chamber of the world is due to be put into operation at the end of 1972. The magnetic flux density of 3.5 T necessary for the detection of the high-energy elementary particles is generated by superconducting coils of 4.7 m inner diameter. The fully stabilized conductor for half of these coils was fabricated from component conductors by longitudinal seam welding with the electron beam under vacuum. The conductor design, the design and the method of operation of the electron beam welding installation and the operating and fabricating experience gained by the processing of approximately 60 t of conductor material are discussed. (7 refs).

  15. Magnetism in Bi2212 and Tl2223 Superconductors: ME Muon-Spin Research

    Science.gov (United States)

    Boekema, Carolus; Lee, J.; Prudchenko, Y.; Li, Y.; Robledo, L.; Launspach, B.

    2004-03-01

    Muon-spin-resonance vortex data of underdoped Bi_2Sr_2CaCu_2Ox (Bi2212) and Tl_2Ba_2Ca_2Cu_3Oy (Tl2223) are analyzed to search for antiferromagnetism (AF) in and around its vortex cores. [1] Using the Maximum-Entropy (ME) technique, the obtained ME transforms reflect the magnetic field distributions in the vortex states. Below T_c, the grainboundary signal near the applied field (5 kOe) is well fitted by a narrow Gaussian. Below 0.5 T_c, vortex signals are better fitted by Lorentzians than expected Gaussians, especially at their high-field sides. Thus, extra AF fields are present in and around the vortex cores. Our ME vortex-core results are compared with those of R1237. [2] Below 0.5 T_c, we found extra inflections at the high field sides for the frequency-derivatives of ME transforms. [1, 2] These effects have been predicted by the theory of Arovas et al. [3] Flux trapping results obtained for zero-field _SR data of field-cooled Tl2223 recorded at 10 K, after the applied field went from 5 to 0 kOe, are reported. Our ME muon-spin research strongly supports a magnetic origin of cuprate superconductivity. Research is supported by NSF-REU, LANL-DOE and by WiSE@SJSU. [1] J. Lee et al, 9th Joint MMM/Intermag (January 2004) Conference, submitted. [2] C. Boekema et al, Int J Modern Phys B17 (2003) 3436. [3] D. Arovas et al, Phys Rev Lett 79 (1997) 2871.

  16. Superconductor Composite

    Science.gov (United States)

    Dorris, Stephen E.; Burlone, Dominick A.; Morgan; Carol W.

    1999-02-02

    A superconducting conductor fabricated from a plurality of wires, e.g., fine silver wires, coated with a superconducting powder. A process of applying superconducting powders to such wires, to the resulting coated wires and superconductors produced therefrom.

  17. Influence of magnetic fields on hysteretic ac losses in bulk MgB{sub 2} superconductor investigated by using Hall probe ac susceptibility method

    Energy Technology Data Exchange (ETDEWEB)

    Varilci, A [Faculty of Arts and Sciences, Department of Physics, Abant Izzet Baysal University, 14280 Bolu (Turkey)

    2007-04-15

    We report the results of an investigation of the influence of magnetic fields on hysteretic ac losses in bulk MgB{sub 2} superconductor by using Hall probe ac susceptibility. The external magnetic field in this study had an ac part with frequency 10 Hz and magnitude in the range 240-1200 A m{sup -1} and no dc part. We have measured the imaginary part of the magnetic susceptibility and analysed data by using Bean's critical state model of cylindrical geometry for four different temperature values 39.55, 39.51, 39.47 and 39.41 K. The result of this analysis indicates that Bean's model is adequate to explain the experimental findings. Calculated hysteretic ac loss versus applied magnetic field curve is given by using the critical state model. We have also measured the magnetization versus applied magnetic field and determined the first critical magnetic field of a MgB{sub 2} sample as 500 A m{sup -1} at 35 K.

  18. Magnetic-field induced superconductor-metal-insulator transitions in bismuth metal-graphite

    Science.gov (United States)

    Suzuki, Masatsugu; Suzuki, Itsuko S.; Lee, Robert; Walter, Jürgen

    2002-03-01

    Bismuth-metal graphite (MG) has a unique layered structure where Bi nanoparticles are encapsulated in nanographites. The size of nanographite is on the same order as that of Bi nanographite. The observed superconductivity below Tc (= 2.48 K) and the Curie-like Pauli paramagnetic susceptibility below 30 K are related to the high density of states at the Fermi energy arising from edge states of nanographites.^1 A magnetic-field induced transition from metallic to semiconductor-like phase is observed in the in-plane resistivity ρa around Hc (≈ 25 kOe) for both H⊥c and H‖c (c: c axis). The suppression of the metallic phase by H is independent of the directions of H (H‖c and H⊥c) for Bi-MG, suggesting that the spin related effect is significant compared to the orbital effect. The Zeemann energy gSμ_BH at 25 kOe corresponds to a thermal energy k_BTH with TH = 1.7 K, where g = 2 and S = 1/2. The temperature TH is slightly lower than T_c. A negative magnetoresistance in ρa for H⊥c (040 kOe) suggest the occurrence of two-dimensional weak localization effect. ^1K. Wakabayashi, M. Fujita, H. Ajiki, and M. Sigrist, Phys. Rev. 59, 8271 (1999).

  19. Magnetic properties of high temperature superconductors. AC susceptibility and magnetostriction studies

    Energy Technology Data Exchange (ETDEWEB)

    Heill, L.K.

    1995-05-01

    The author of this thesis has measured the ac magnetic response function {mu} = {mu}`+i{mu}`` in melt-powder-melt-growth YBa{sub 2}Cu{sub 3}O{sub 7} (Y123) with insulating Y{sub 2}BaCuO{sub 5} (Y211) and in single crystal YBa{sub 2}Cu{sub 3}O{sub 7} (SC) in applied dc fields up to 8 T, oriented both parallel and perpendicular to the crystalline c-axis. Both samples are cubes with sides of about 1 mm. The response of the two samples was mapped out as a function of temperature, excitation field amplitude and frequency, dc field and field orientation. It is found that for both samples the loss peak line (LPL) and hence the irreversibility line (IL) exists at higher temperatures and fields for perpendicular field orientation than for parallel. Strong frequency but weak amplitude dependence is observed for parallel orientation, vice versa for perpendicular orientation. The measured response is strongly non-linear for perpendicular orientation, and intermediate between linear (ohmic) and extremely non-linear (Bean critical state) for parallel orientation. The situation at parallel orientation is close to but above the transition into a vortex solid state, and a power law temperature dependence with exponent 1.5 is obtained for the vortex glass transition line. For perpendicular orientation the response is consistent with that expected in a vortex solid. Pinning barriers are found by means of thermal activation analysis. Anomalous loss peaks {mu}``(T) are observed for the SC sample for intermediate fields in perpendicular orientation. Large magnetostriction is found in a flat single crystal Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} sample at low temperature and fields up to 6 T applied along the c-axis. 332 refs., 59 figs., 7 tabs.

  20. Atomic scale visualization of novel magnetic phase transitions in Fe-based superconductor Sr4V2O6Fe2As2

    Science.gov (United States)

    Choi, Seokhwan; Jang, Won-Jun; Ok, Jong Mok; Choi, Hyun Woo; Lee, Hyun Jung; Jung, Jin Oh; Son, Dong Hyun; Suh, Hwan Soo; Kim, Jun Sung; Semertzidis, Yannis K.; Lee, Jhinhwan

    Sr4V2O6Fe2As2 consists of superconducting FeAs layers and Mott insulating Sr2VO3 layers, and exhibits superconductivity with Tc near 30 K despite being a parent compound material. Unlike normal Fe-based superconductors, the magnetism of Sr4V2O6Fe2As2 has complexity due to the presence of two magnetic atomic layers of V and Fe; therefore, the issue of magnetism has been actively debated. In this work, we studied the orbital and magnetic phase transitions in the range of 4 K to 180 K using spin-polarized scanning tunneling microscope. We directly observed the changes of charge density waves of V atomic layer related to the nematicity at 150 K, and spin density waves of V atomic layer resulting from spin ordering of underlying Fe atomic layer below 50 K. Moreover, controlling the sample bias voltage, the hysteresis of magnetic domain is observed at 4 K. Our results show key clues to solve controversy about the magnetism of Sr4V2O6Fe2As2.

  1. High-energy magnetic excitations in the cuprate superconductor Bi(2)Sr(2)CaCu(2)O(8+δ): towards a unified description of its electronic and magnetic degrees of freedom.

    Science.gov (United States)

    Dean, M P M; James, A J A; Springell, R S; Liu, X; Monney, C; Zhou, K J; Konik, R M; Wen, J S; Xu, Z J; Gu, G D; Strocov, V N; Schmitt, T; Hill, J P

    2013-04-05

    We investigate the high-energy magnetic excitation spectrum of the high-T(c) cuprate superconductor Bi(2)Sr(2)CaCu(2)O(8+δ) (Bi-2212) using Cu L(3) edge resonant inelastic x-ray scattering. Broad, dispersive magnetic excitations are observed, with a zone boundary energy of ∼ 300 meV and a weak dependence on doping. These excitations are strikingly similar to the bosons proposed to explain the high-energy "kink" observed in photoemission. A phenomenological calculation of the spin response, based on a parametrization of the the angle-resolved photoemission spectroscopy derived electronic structure and Yang-Rice-Zhang quasiparticles, provides a reasonable prediction of the energy dispersion of the observed magnetic excitations. These results indicate a possible unified framework to reconcile the magnetic and electronic properties of the cuprates and we discuss the advantages and disadvantages of such an approach.

  2. Persistent magnetism in silver-doped BaF e2A s2 crystals

    Science.gov (United States)

    Li, Li; Cao, Huibo; Parker, David S.; Kuhn, Stephen J.; Sefat, Athena S.

    2016-10-01

    We investigate the thermodynamic and transport properties of silver-substituted BaF e2A s2 (122) crystals up to ˜4.5 % . Similar to other transition-metal substitutions in 122, Ag diminishes the antiferromagnetic (TN) and structural (TS) transition temperatures, but unlike other electron-doped 122s, TN and TS coincide without splitting. Although magnetism drops precipitously to TN= 84 K at doping x =0.029 , it only weakly changes above this x , settling at TN= 80 K at x =0.045 . Compared to this persistent magnetism in Ag-122, doping other group 11 elements of either Cu or Au in 122 diminished TN and induced superconductivity near Tc= 2 K at x =0.044 or 0.031, respectively. Ag-122 crystals show reflective surfaces with surprising thicker cross sections for x ≥0.019 , the appearance that is in contrast to the typical thin stacked layered feature seen in all other flux-grown x122 and lower Ag-122. This physical trait may be a manifest of intrinsic weak changes in c lattice and TN. Our theoretical calculations suggest that Ag doping produces strong electronic scattering and yet a relatively small disruption of the magnetic state, both of which preclude superconductivity in this system.

  3. Magnetic hysteresis of the zero-resistance critical temperature of high-T{sub c} granular superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Flores, L.; Altshuler, E.; Garcia, S. [Univ. of Havana (Cuba)] [and others

    1995-10-01

    The authors have found a notorious hysteretic behavior in the dependence of the zero-resistance critical temperature obtained through resistivity ({rho}) versus temperature (T) measurements with applied field (H{sub c}) in High-T{sub c} granular superconductors. This behavior is explained semi-quantitatively based on the analogy between the present observation and a similar hysteresis found in the field dependence of the transport critical current in these materials.

  4. Vortices and nanostructured superconductors

    CERN Document Server

    2017-01-01

    This book provides expert coverage of modern and novel aspects of the study of vortex matter, dynamics, and pinning in nanostructured and multi-component superconductors. Vortex matter in superconducting materials is a field of enormous beauty and intellectual challenge, which began with the theoretical prediction of vortices by A. Abrikosov (Nobel Laureate). Vortices, vortex dynamics, and pinning are key features in many of today’s human endeavors: from the huge superconducting accelerating magnets and detectors at the Large Hadron Collider at CERN, which opened new windows of knowledge on the universe, to the tiny superconducting transceivers using Rapid Single Flux Quanta, which have opened a revolutionary means of communication. In recent years, two new features have added to the intrinsic beauty and complexity of the subject: nanostructured/nanoengineered superconductors, and the discovery of a range of new materials showing multi-component (multi-gap) superconductivity. In this book, leading researche...

  5. Persistent cloaca presenting with a perineal cyst: Prenatal ultrasound and magnetic resonance imaging findings

    Directory of Open Access Journals (Sweden)

    Chih-Ping Chen

    2012-04-01

    Full Text Available A 40-year-old, primigravid woman presented at 23 weeks of gestation for evaluation of an extra-abdominal echogenic cystic mass of the fetus. Amniocentesis revealed a karyotype of 46,XX. Prenatal ultrasound showed a two-vessel umbilical cord, hydrocolpos, and distended bladder, urethra, and colon, and a perineal cystic mass. The kidneys and amniotic fluid amount were normal. Fetal magnetic resonance imaging revealed ascites, hydrocolpos, distended urinary bladder and colon, high rectum, and a perineal cyst. The fetus postnatally manifested persistent cloaca. The perineum was distended and smooth, without patent anal, vaginal, and urethral openings. The external genitalia were ambiguous with no labia majora, labia minora, or clitoris. The perineal cyst had a very small single orifice. We suggest that cloacal anomalies be considered in any female fetus with hydrocolpos, distended bladder and colon, ascites, and a perineal cyst.

  6. Superconductor cable

    Science.gov (United States)

    Allais, Arnaud; Schmidt, Frank; Marzahn, Erik

    2010-05-04

    A superconductor cable is described, having a superconductive flexible cable core (1) , which is laid in a cryostat (2, 3, 4), in which the cable core (1) runs in the cryostat (2, 3, 4) in the form of a wave or helix at room temperature.

  7. Superconductor stability, 1983: a review

    Energy Technology Data Exchange (ETDEWEB)

    Dresner, L.

    1983-01-01

    Three main topics have been discussed in this paper, namely, internally cooled superconductors, cooling by superfluid helium, and metastable magnets. The discussion of each has centered around a dominant idea, and it is fitting to highlight these ideas by way of conclusion. With regard to internally cooled superconductors, most of what we have learned in the last few years centers on the strong motion caused by the thermal expansion of helium. How naive were our early calculations that treated the helium as though it were incompressible. Our discussion of He-II was organized around the Gorter-Mellink relation and the solutions of the nonlinear diffusion equation it gives rise to. And our discussion of metastable magnets revolved around the fruitful concept of the MPZ. These three ideas are sturdy trunks that support much of the thought about superconductor stability that has flowered in the past several years.

  8. De-Sitter spacetime as a superconductor

    CERN Document Server

    Momeni, D

    2016-01-01

    A superconductor is a material with infinite electric conductivity. Superconductivity and magnetism are happening as two opposite phenomena: superconductors need weak external magnetic fields (the Meissner effect) while generally with a strong external magnetic field we loose superconductivity. In \\cite{ref:I}-\\cite{Chernodub:2011tv} , the author showed that a very strong magnetic field can turn an empty space into a superconductor. We extended this idea to the constant curvature spaces, de Sitter (dS) spacetime and by a careful analysis of the modes for a spinor with arbitrary spin, we show that in a very similar condensation scenario as was proposed for flat space, we could transform dS to a superconductor.

  9. Fast recovery of the stripe magnetic order by Mn/Fe substitution in F-doped LaFeAsO superconductors

    Science.gov (United States)

    Moroni, M.; Carretta, P.; Allodi, G.; De Renzi, R.; Gastiasoro, M. N.; Andersen, B. M.; Materne, P.; Klauss, H.-H.; Kobayashi, Y.; Sato, M.; Sanna, S.

    2017-05-01

    75As nuclear magnetic (NMR) and quadrupolar (NQR) resonance were used, together with Mössbauer spectroscopy, to investigate the magnetic state induced by Mn for Fe substitutions in F-doped LaFe1 -xMnxAsO superconductors. The results show that 0.5% of Mn doping is enough to suppress the superconducting transition temperature Tc from 27 K to zero and to recover the magnetic structure observed in the parent undoped LaFeAsO. Also the tetragonal to orthorhombic transition of the parent compound is recovered by introducing Mn, as evidenced by a sharp drop of the NQR frequency. The NQR spectra also show that a charge localization process is at play in the system. Theoretical calculations using a realistic five-band model show that correlation-enhanced RKKY exchange interactions between nearby Mn ions stabilize the observed stripe magnetic order. These results give compelling evidence that F-doped LaFeAsO is a strongly correlated electron system at the verge of an electronic instability.

  10. Orientation and thickness dependence of magnetic levitation force and trapped magnetic field of single grain YBa{sub 2}Cu{sub 3}O{sub 7-y} bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Y.; Go, S. J.; Joo, H. T. [Korea Science Academy of Korea Advanced Institute of Science and Technology, Pusan (Korea, Republic of); Lee, Y. J.; Park, S. D.; Jun, B. H.; KIm, C. J. [Neutron Utilization Technology Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-03-15

    The effects of the crystallographic orientation and sample thickness on the magnetic levitation forces (F) and trapped magnetic field (B) of single grain YBCO bulk superconductors were examined. Single grain YBCO samples with a (001), (110) or (100) surface were used as the test samples. The samples used for the force-distance (F-d) measurement were cooled at 77 K without a magnetic field (zero field cooling, ZFC), whereas the samples used for the B measurement were cooled under the external magnetic field of a Nd-B-Fe permanent magnet (field cooling, FC). It was found that F and B of the (001) surface were higher than those of the (110) or (100) surface, which is attributed to the higher critical current density (J{sub c}) of the (001) surface. For the (001) samples with t=5–18 mm, the maximum magnetic levitation forces (F{sub max}s) of the ZFC samples were larger than 40 N. About 80% of the applied magnetic field was trapped in the FC samples. However, the F and B decreased rapidly as t decreased below 5 mm. There exists a critical sample thickness (t=5 mm for the experimental condition of this study) for maintaining the large levitation/trapping properties, which is dependent on the material properties and magnitude of the external magnetic fields.

  11. The effects of magnetic field and temperature quenches on non-equilibrium relaxation properties of vortex lines in type-II superconductors

    Science.gov (United States)

    Assi, Hiba; Dobramysl, Ulrich; Pleimling, Michel; Täuber, Uwe

    2014-03-01

    Technological applications of type-II superconductors require a deep understanding of the dynamics of vortex matter in these complex materials. We model vortices in the London limit as interacting elastic lines, and simulate their dynamics employing a Langevin molecular dynamics (LMD) algorithm. This LMD algorithm is utilized to investigate the non-equilibrium relaxation properties of interacting lines, subject to randomly-placed point or correlated columnar pinning sites, by studying various two-time correlation functions. We consider experimentally-motivated initial conditions by applying quenches in the system temperature or the magnetic field, which is realized by suddenly adding or removing vortex lines from the system. Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-09ER46613.

  12. Modified Bean Model and FEM Method Combined for Persistent Current Calculation in Superconducting Coils

    CERN Document Server

    Völlinger, Christine; Russenschuck, Stephan

    2001-01-01

    Field variations in the LHC superconducting magnets, e. g. during the ramping of the magnets, induce magnetization currents in the superconducting material, the so-called persistent currents that do not decay but persist due to the lack of resistivity. This paper describes a semi-analytical hysteresis model for hard superconductors, which has been developed for the computation of the total field errors arising from persistent currents. Since the superconducting coil is surrounded by a ferromagnetic yoke structure, the persistent current model is combined with the finite element method (FEM), as the non-linear yoke can only be calculated numerically. The used finite element method is based on a reduced vector potential formulation that avoids the meshing of the coil while calculating the part of the field arising from the source currents by means of the Biot-Savart Law. The combination allows to determine persistent current induced field errors as function of the excitation and for arbitrarily shaped iron yoke...

  13. Impact of catheter ablation with remote magnetic navigation on procedural outcomes in patients with persistent and long-standing persistent atrial fibrillation

    DEFF Research Database (Denmark)

    Jin, Qi; Pehrson, Steen; Jacobsen, Peter Karl;

    2015-01-01

    BACKGROUND: The objectives of this study were to assess the procedural outcomes of persistent and long-standing persistent atrial fibrillation (PsAF and L-PsAF) ablation guided by remote magnetic navigation (RMN), and to detect factors predicting acute restoration of sinus rhythm (SR) by ablation...... with RMN. METHODS: A total of 313 patients (275 male, age 59 ± 9.5 years) with PsAF (187/313) or L-PsAF (126/313) undergoing ablation using RMN were included. Patients' disease history, pulmonary venous anatomy, left atrial (LA) volume, procedure time, mapping plus ablation time, radiofrequency (RF.......03). Stepwise regression analysis showed LA volume was the primary parameter affecting SR restoration (P = 0.01). The LA volume of patients without direct SR restoration by ablation was 24% greater than that of patients with SR restoration (P RMN is a safe...

  14. Josephson current in a normal-metal nanowire coupled to a superconductor/ferromagnet/superconductor junction

    NARCIS (Netherlands)

    Ebisu, H.; Lu, B.; Taguchi, K.; Golubov, Alexandre Avraamovitch; Tanaka, Y.

    2016-01-01

    We consider a superconducting nanowire proximity coupled to a superconductor/ferromagnet/superconductor (S/F/S) junction, where the magnetization penetrates into a superconducting segment in a nanowire decaying as ∼exp[−∣n∣ξ], where n is the site index and the ξ is the decay length. We tune chemical

  15. Quantum mechanics and the second law of thermodynamics: an insight gleaned from magnetic hysteresis in the first order phase transition of an isolated mesoscopic-size type I superconductor

    Science.gov (United States)

    Keefe, Peter D.

    2012-11-01

    J Bardeen proposed that the adiabatic phase transition of mesoscopic-size type I superconductors must be accompanied by magnetic hysteresis in the critical magnetic field of sufficient magnitude to satisfy the second law of thermodynamics, herein referred to as ‘Bardeen Hysteresis’. Bardeen Hysteresis remains speculative in that it has not been reported in the literature. This paper investigates Bardeen Hysteresis as a possible accompaniment to the adiabatic phase transition of isolated mesoscopic-size type I superconductors and its implications with respect to the second law of thermodynamics. A causal mechanism for Bardeen Hysteresis is discussed which contrasts with the long accepted causal mechanism of magnetic hysteresis, as first summarized by Pippard, herein referred to as ‘Pippard Hysteresis’. The paper offers guidance for an experimental verification and comments on how the existence of Bardeen Hysteresis has relation to a quantum mechanical basis for the second law of thermodynamics.

  16. Thallium 2223 high Tc superconductor in a silver matrix and its magnetic shielding, hermal cycle and time aging properties

    Energy Technology Data Exchange (ETDEWEB)

    Fei, X.; He, W.S.; Havenhill, A. [and others

    1994-12-31

    Superconducting Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} (Tl2223) was ground to powder. Mixture with silver powder (0--80% weight) and press to desired shape. After proper annealing, one can get good silver-content Tl2223 bulk superconductor. It is time-stable and has good superconducting property as same as pure Tl2223. It also has better mechanical property and far better thermal cycle property than pure Tl2223.

  17. Effects of flux motion on the electrical conduction in some granular high T sub c superconductors- studies in low and moderate magnetic fields

    CERN Document Server

    Asim, M M

    1996-01-01

    gamma. The field dependence of gamma has been found to the H-1/3 consistent with some previously reported results obtained by others in the low field region. At low angles the angular part of the dissipation shows deviations from sin/sup 2/theta, as well as hysteresis. This low angle anomaly was thoroughly studied at different currents, fields and temperatures and interpreted as an effect of Lorentz force mediated flux redistribution between inter and intra-grain regions. A magnetization model was developed to incorporate both the equilibrium and non equilibrium parts of magnetization in the granular samples. The data were fit to M(H) and the values of H sub c sub 2 (T) obtained. (Orig./A.B.) Experimental work has been carried out on YBCO and BSCCO based granular high T/sub c/ superconductors to explore the mechanism of conduction in applied magnetic field. DC resistivity technique has been employed to observe the details of dissipation, dependent and independent of the mutual orientation theta of J and B. Bo...

  18. Bulk high-T{sub c} superconductors with drilled holes: how to arrange the holes to maximize the trapped magnetic flux?

    Energy Technology Data Exchange (ETDEWEB)

    Lousberg, Gregory P [SUPRATECS Research Group, Department of Electrical Engineering and Computer Science (B28), University of Liege (Belgium); Ausloos, M [SUPRATECS, Department of Physics (B5), University of Liege (Belgium); Vanderbemden, Ph [SUPRATECS Research Group, Department of Electrical Engineering and Computer Science (B28), University of Liege (Belgium); Vanderheyden, B [SUPRATECS Research Group, Department of Electrical Engineering and Computer Science (B28), University of Liege (Belgium)

    2008-02-15

    Drilling holes in a bulk high-T{sub c} superconductor enhances the oxygen annealing and the heat exchange with the cooling liquid. However, drilling holes also reduces the amount of magnetic flux that can be trapped in the sample. In this paper, we use the Bean model to study the magnetization and the current line distribution in drilled samples, as a function of the hole positions. A single hole perturbs the critical current flow over an extended region that is bounded by a discontinuity line, where the direction of the current density changes abruptly. We demonstrate that the trapped magnetic flux is maximized if the centre of each hole is positioned on one of the discontinuity lines produced by the neighbouring holes. For a cylindrical sample, we construct a polar triangular hole pattern that exploits this principle; in such a lattice, the trapped field is {approx}20% higher than in a squared lattice, for which the holes do not lie on discontinuity lines. This result indicates that one can simultaneously enhance the oxygen annealing, the heat transfer and maximize the trapped field.

  19. Current induced magnetic flux response in frustrated three-band superconductors as a bulk probe of broken time reversal symmetry (BTRS) ground states

    Energy Technology Data Exchange (ETDEWEB)

    Yerin, Yuriy; Omelyanchouk, Alexander [Verkin Inst. for Low Temperature Physics and Engineering. 61103 Kharkiv (Ukraine); Drechsler, Stefan-Ludwig; Brink, Jeroen van den; Efremov, Dmitriy [Inst. for Theorretical Solid State Physics at the Leibniz Inst. for Solid State an Materials Research, IFW-Dresden, D-01171 Dresden (Germany)

    2016-07-01

    Within the Ginzburg-Landau formalism we provide a classification of all possible ground states (GS) of a three-band superconductor (3BSC) where either frustrated states with BTRS or a single non-BTRS GS with unconventional/conventional s-wave symmetry, respectively, exist. The necessary condition for a BTRS GS in general cannot be reduced to a ''-''sign of the product of all interband couplings (IBC) valid in the case of 3 equivalent bands with repulsive equal IBC, only. It corresponds to a maximal IBC frustration. We show that with increasing diversity of the parameter space this frustration is reduced and the regions of possible BTRS GS start to shrink. We track possible evolutions of a BTRS GS of a 3BSC based doubly-connected system in an external magnetic field. Depending on its parameters, a magnetic flux can induce various current density leaps, connected with adiabatic or non-adiabatic transitions from BTRS to non-BTRS states and vice versa. The current induced magnetic flux response of samples with a doubly-connected geometry e.g. as a thin tube provides a suitable experimental tool for the detection of BTRS GS.

  20. Topological Aspects of Triplet Superconductors

    Institute of Scientific and Technical Information of China (English)

    REN Ji-Rong; XU Dong-Hui; ZHANG Xin-Hui; LI Ran

    2007-01-01

    In this paper, using the φ-mapping theory, it is shown that two kinds of topological defects, i.e., the vortex lines and the monopoles exist in the helical configuration of magnetic field in triplet superconductors. And the inner topological structure of these defects is studied. Because the knot solitons in the triplet superconductors are characterized by the Hopf invariant, we also establish a relationship between the Hopf invariant and the linking number of knots family,and reveal the inner topological structure of the Hopf invariant.

  1. A trapped magnetic field of 3 T in homogeneous, bulk MgB2 superconductors fabricated by a modified precursor infiltration and growth process

    Science.gov (United States)

    Bhagurkar, A. G.; Yamamoto, A.; Anguilano, L.; Dennis, A. R.; Durrell, J. H.; Babu, N. Hari; Cardwell, D. A.

    2016-03-01

    The wetting of boron with liquid magnesium is a critical factor in the synthesis of MgB2 bulk superconductors by the infiltration and growth (IG) process. Poor wetting characteristics can therefore result potentially in non-uniform infiltration, formation of defects in the final sample structure and poor structural homogeneity throughout the bulk material. Here we report the fabrication of near-net-shaped MgB2 bulk superconductors by a modified precursor infiltration and growth (MPIG) technique. A homogeneous bulk microstructure has subsequently been achieved via the uniform infiltration of Mg liquid by enriching pre-reacted MgB2 powder within the green precursor pellet as a wetting enhancer, leading to relatively little variation in superconducting properties across the entire bulk sample. Almost identical values of trapped magnetic field of 2.12 T have been measured at 5 K at both the top and bottom surfaces of a sample fabricated by the MPIG process, confirming the uniformity of the bulk microstructure. A maximum trapped field of 3 T has been measured at 5 K at the centre of a stack of two bulk MgB2 samples fabricated using this technique. A steady rise in trapped field was observed for this material with decreasing temperature down to 5 K without the occurrence of flux avalanches and with a relatively low field decay rate (1.5%/d). These properties are attributed to the presence of a fine distribution of residual Mg within the bulk microstructure generated by the MPIG processing technique.

  2. Topological insulators and topological superconductors

    CERN Document Server

    Bernevig, Andrei B

    2013-01-01

    This graduate-level textbook is the first pedagogical synthesis of the field of topological insulators and superconductors, one of the most exciting areas of research in condensed matter physics. Presenting the latest developments, while providing all the calculations necessary for a self-contained and complete description of the discipline, it is ideal for graduate students and researchers preparing to work in this area, and it will be an essential reference both within and outside the classroom. The book begins with simple concepts such as Berry phases, Dirac fermions, Hall conductance and its link to topology, and the Hofstadter problem of lattice electrons in a magnetic field. It moves on to explain topological phases of matter such as Chern insulators, two- and three-dimensional topological insulators, and Majorana p-wave wires. Additionally, the book covers zero modes on vortices in topological superconductors, time-reversal topological superconductors, and topological responses/field theory and topolo...

  3. Superconducting pulsed magnets

    CERN Document Server

    CERN. Geneva

    2006-01-01

    Lecture 1. Introduction to Superconducting Materials Type 1,2 and high temperature superconductors; their critical temperature, field & current density. Persistent screening currents and the critical state model. Lecture 2. Magnetization and AC Loss How screening currents cause irreversible magnetization and hysteresis loops. Field errors caused by screening currents. Flux jumping. The general formulation of ac loss in terms of magnetization. AC losses caused by screening currents. Lecture 3. Twisted Wires and Cables Filamentary composite wires and the losses caused by coupling currents between filaments, the need for twisting. Why we need cables and how the coupling currents in cables contribute more ac loss. Field errors caused by coupling currents. Lecture 4. AC Losses in Magnets, Cooling and Measurement Summary of all loss mechanisms and calculation of total losses in the magnet. The need for cooling to minimize temperature rise in a magnet. Measuring ac losses in wires and in magnets. Lecture 5. Stab...

  4. Iron pnictide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tegel, Marcus Christian

    2011-03-22

    The scope of this dissertation therefore has not only been the synthesis of various new superconducting and non-superconducting iron pnictides of several structural families but also their in-depth crystallographic and physical characterisation. In Chapters 3 - 6, the family of the ZrCuSiAs-type (1111) compounds is subject of discussion. The solid solution series La(Co{sub x}Fe{sub 1-x})PO is analysed regarding magnetic and superconducting properties and the new compounds EuMnPF and REZnPO, as well as the new superconductor parent compound SrFeAsF are presented. Chapters 7 - 9 are dedicated to the new iron arsenide superconductors of the ThCr{sub 2}Si{sub 2}-type (122 family). Therein, also the discovery of the first superconductor in this structural family, Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, is unveiled. A detailed examination of the complete solid solution series (Ba{sub 1-x}K{sub x})Fe{sub 2}As{sub 2} is presented. Moreover, the crystallographic phase transitions of the closely related compounds SrFe{sub 2}As{sub 2} and EuFe{sub 2}As{sub 2} are characterised and the superconductors Sr{sub 1-x}K{sub x}Fe{sub 2}As{sub 2} and Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} are examined for magnetic and phononic excitations. In Chapter 10, the redetermined crystal structure of the superconductor Fe(Se{sub 1-x}Te{sub x}) (11-type) is presented from a chemist's point of view. Chapters 11 - 14 look into the superconducting and non-superconducting iron arsenides of more complex structural families (32522-type and 21311-type). Therein, crystallographic and magnetic details of Sr{sub 3}Sc{sub 2}O{sub 5}Fe{sub 2}As{sub 2} are presented and Ba{sub 2}ScO{sub 3}FeAs and Sr{sub 2}CrO{sub 3}FeAs, the first two members of the new 21311-type are portrayed. Sr{sub 2}CrO{sub 3}FeAs is looked at in close detail with various methods, so e.g. the spin structure of the magnetically ordered compound is solved and a possible reason for the absence of superconductivity in this compound

  5. Second magnetization peak effect, vortex dynamics, and flux pinning in 112-type superconductor Ca0.8La0.2Fe(1-x)CoxAs2.

    Science.gov (United States)

    Zhou, Wei; Xing, Xiangzhuo; Wu, Wenjuan; Zhao, Haijun; Shi, Zhixiang

    2016-01-01

    Investigation of vortex pinning and its relaxation is of great importance for both basic physics and technological applications in the field of superconductivity. We report a great improvement of superconducting properties in the recently discovered 112-type superconductors (Ca, La)FeAs2 through Co co-doping. High critical current density Js(5 K) > 2(*)10(6) A/cm(2) is obtained and pronounced second peak effect is observed in magnetization hysteresis loops. Both the dynamic and static relaxation studies result in comparable and sizable relaxation rates S or Q, indicating a fast vortex creep. The second magnetization peak (SMP) is found to be strongly associated with a crossover from elastic to plastic vortex creep. Above the crossover, plastic vortex creep governs the vortex dynamics in a wide range of temperatures and fields. A good scaling behavior of the normalized pinning force density fp by formula fp = h(p)(1-h)(q) ((p) = 1.44, q = 1.66, h = 0.44) is revealed, which demonstrates an important contribution from core normal point-like pinning sites. To better understand the SMP phenomenon, we discuss the related physical scenario as well as the affecting factors in the SMP occurrence.

  6. Second magnetization peak effect, vortex dynamics, and flux pinning in 112-type superconductor Ca0.8La0.2Fe1-xCoxAs2

    Science.gov (United States)

    Zhou, Wei; Xing, Xiangzhuo; Wu, Wenjuan; Zhao, Haijun; Shi, Zhixiang

    2016-03-01

    Investigation of vortex pinning and its relaxation is of great importance for both basic physics and technological applications in the field of superconductivity. We report a great improvement of superconducting properties in the recently discovered 112-type superconductors (Ca, La)FeAs2 through Co co-doping. High critical current density Js(5 K) > 2*106 A/cm2 is obtained and pronounced second peak effect is observed in magnetization hysteresis loops. Both the dynamic and static relaxation studies result in comparable and sizable relaxation rates S or Q, indicating a fast vortex creep. The second magnetization peak (SMP) is found to be strongly associated with a crossover from elastic to plastic vortex creep. Above the crossover, plastic vortex creep governs the vortex dynamics in a wide range of temperatures and fields. A good scaling behavior of the normalized pinning force density fp by formula fp = hp(1-h)q (p = 1.44, q = 1.66, h = 0.44) is revealed, which demonstrates an important contribution from core normal point-like pinning sites. To better understand the SMP phenomenon, we discuss the related physical scenario as well as the affecting factors in the SMP occurrence.

  7. Determining the in-plane Fermi surface topology in high T(c) superconductors using angle-dependent magnetic quantum oscillations.

    Science.gov (United States)

    Harrison, N; McDonald, R D

    2009-05-13

    We propose a quantum oscillation experiment by which the rotation of an underdoped YBa(2)Cu(3)O(6+x) sample about two different axes with respect to the orientation of the magnetic field can be used to infer the shape of the in-plane cross-section of corrugated Fermi surface cylinder(s). Deep corrugations in the Fermi surface are expected to give rise to nodes in the quantum oscillation amplitude that depend on the magnitude and orientation of the magnetic induction B. Because the symmetries of electron and hole cylinders within the Brillouin zone are expected to be very different, the topology can provide essential clues as to the broken symmetry responsible for the observed oscillations. The criterion for the applicability of this method to the cuprate superconductors (as well as other layered metals) is that the difference in quantum oscillation frequency 2ΔF between the maximum (belly) and minimum (neck) extremal cross-sections of the corrugated Fermi surface exceeds |B|.

  8. Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2

    Science.gov (United States)

    Kittaka, Shunichiro; Aoki, Yuya; Shimura, Yasuyuki; Sakakibara, Toshiro; Seiro, Silvia; Geibel, Christoph; Steglich, Frank; Tsutsumi, Yasumasa; Ikeda, Hiroaki; Machida, Kazushige

    2016-08-01

    This paper presents the results of specific-heat and magnetization measurements, in particular their field-orientation dependence, on the first discovered heavy-fermion superconductor CeCu2Si2 (Tc˜0.6 K). We discuss the superconducting gap structure and the origin of the anomalous pair-breaking phenomena, leading, e.g., to the suppression of the upper critical field Hc 2, found in the high-field region. The data show that the anomalous pair breaking becomes prominent below about 0.15 K in any field direction, but occurs closer to Hc 2 for H ∥c . The presence of this anomaly is confirmed by the fact that the specific-heat and magnetization data satisfy standard thermodynamic relations. Concerning the gap structure, field-angle dependencies of the low-temperature specific heat within the a b and a c planes do not show any evidence for gap nodes. From microscopic calculations in the framework of a two-band full-gap model, the power-law-like temperature dependencies of C and 1 /T1 , reminiscent of nodal superconductivity, have been reproduced reasonably. These facts further support multiband full-gap superconductivity in CeCu2Si2 .

  9. Ramping turn-to-turn loss and magnetization loss of a No-Insulation (RE)Ba2Cu3Ox high temperature superconductor pancake coil

    Science.gov (United States)

    Wang, Y.; Song, H.; Yuan, W.; Jin, Z.; Hong, Z.

    2017-03-01

    This paper is to study ramping turn-to-turn loss and magnetization loss of a no-insulation (NI) high temperature superconductor (HTS) pancake coil wound with (RE)Ba2Cu3Ox (REBCO) conductors. For insulated (INS) HTS coils, a magnetization loss occurs on superconducting layers during a ramping operation. For the NI HTS coil, additional loss is generated by the "bypassing" current on the turn-to-turn metallic contacts, which is called "turn-to-turn loss" in this study. Therefore, the NI coil's ramping loss is much different from that of the INS coil, but few studies have been reported on this aspect. To analyze the ramping losses of NI coils, a numerical method is developed by coupling an equivalent circuit network model and a H-formulation finite element method model. The former model is to calculate NI coil's current distribution and turn-to-turn loss, and the latter model is to calculate the magnetization loss. A test NI pancake coil is wound with REBCO tapes and the reliability of this model is validated by experiments. Then the characteristics of the NI coil's ramping losses are studied using this coupling model. Results show that the turn-to-turn loss is much higher than the magnetization loss. The NI coil's total ramping loss is much higher than that of its insulated counterpart, which has to be considered carefully in the design and operation of NI applications. This paper also discusses the possibility to reduce NI coil's ramping loss by decreasing the ramping rate of power supply or increasing the coil's turn-to-turn resistivity.

  10. Factors affecting characterization of bulk high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hull, J.R. [Argonne National Lab., IL (United States). Energy Technology Div.

    1997-11-01

    Three major factors affect the characterization of bulk high-temperature superconductors in terms of their levitation properties during interaction with permanent magnets. First, the appropriate parameter for the permanent magnet is internal magnetization, not the value of the magnetic field measured at the magnet`s surface. Second, although levitation force grows with superconductor thickness and surface area, for a given permanent magnet size, comparison of levitation force between samples is meaningful when minimum values are assigned to the superconductor size parameters. Finally, the effect of force creep must be considered when time-averaging the force measurements. In addition to levitational force, the coefficient of friction of a levitated rotating permanent magnet may be used to characterize the superconductor.

  11. The thickness optimization of the magnet and superconductor in HTS maglev system%单块磁悬浮系统磁体和超导体的厚度优化

    Institute of Scientific and Technical Information of China (English)

    付志方; 赵立峰; 马家庆; 张勇; 赵勇

    2013-01-01

    The effect of thickness of magnets and YBCO superconductor bulks on suspended force was studied in this paper. Levitation forces of superconductor bulks with different thickness above magnets of φ>30mm × 18mm and φ30mm × 10mm were examined , respectively. The optimal values of the thickness of the magnet and superconductor bulks were thus obtained. Furthermore , vibration responses of the levitation systems mentioned above were also studied, and the best combination of magnet and superconductor bulk was obtained according to spectrum analysis.%研究了磁铁厚度和YBCO超导体厚度对悬浮力的大小及系统动态特性的影响,通过分析得出磁悬浮系统中磁体和超导体厚度的最优值.通过悬浮力测试系统测得超导块尺寸为φ30mm×18mm时四块不同厚度的磁体的悬浮力以及磁体尺寸为φ30mm × 10mm时六块不同厚度的YBCO超导体的悬浮力的大小;并在振动实验台上测试了上述情况下的振动特性.对动态曲线进行频谱分析,最终得出最优组合,从而对磁悬浮系统的磁体和超导体厚度进行了优化.

  12. Shielding superconductors with thin films

    CERN Document Server

    Posen, Sam; Catelani, Gianluigi; Liepe, Matthias U; Sethna, James P

    2015-01-01

    Determining the optimal arrangement of superconducting layers to withstand large amplitude AC magnetic fields is important for certain applications such as superconducting radiofrequency cavities. In this paper, we evaluate the shielding potential of the superconducting film/insulating film/superconductor (SIS') structure, a configuration that could provide benefits in screening large AC magnetic fields. After establishing that for high frequency magnetic fields, flux penetration must be avoided, the superheating field of the structure is calculated in the London limit both numerically and, for thin films, analytically. For intermediate film thicknesses and realistic material parameters we also solve numerically the Ginzburg-Landau equations. It is shown that a small enhancement of the superheating field is possible, on the order of a few percent, for the SIS' structure relative to a bulk superconductor of the film material, if the materials and thicknesses are chosen appropriately.

  13. Vortex loops entry into type-II superconductors

    CERN Document Server

    Samokhvalov, A V

    1996-01-01

    The magnetic field distribution, the magnetic flux, and the free energy of an Abrikosov vortex loop near a flat surface of type--II superconductors are calculated in the London approximation. The shape of such a vortex line is a semicircle of arbitrary radius. The interaction of the vortex half--ring and an external homogeneous magnetic field applied along the surface is studied. The magnitude of the energy barrier against the vortex expansion into superconductor is found. The possibilities of formation of an equilibrium vortex line determined by the structure of the applied magnetic field by creating the expanding vortex loops near the surface of type--II superconductor are discussed.

  14. Interplay between Magnetism, Superconductivity, and Orbital Order in 5-Pocket Model for Iron-Based Superconductors: Parquet Renormalization Group Study.

    Science.gov (United States)

    Classen, Laura; Xing, Rui-Qi; Khodas, Maxim; Chubukov, Andrey V

    2017-01-20

    We report the results of the parquet renormalization group (RG) analysis of the phase diagram of the most general 5-pocket model for Fe-based superconductors. We use as an input the orbital structure of excitations near the five pockets made out of d_{xz}, d_{yz}, and d_{xy} orbitals and argue that there are 40 different interactions between low-energy fermions in the orbital basis. All interactions flow under the RG, as one progressively integrates out fermions with higher energies. We find that the low-energy behavior is amazingly simple, despite the large number of interactions. Namely, at low energies the full 5-pocket model effectively reduces either to a 3-pocket model made of one d_{xy} hole pocket and two electron pockets or a 4-pocket model made of two d_{xz}/d_{yz} hole pockets and two electron pockets. The leading instability in the effective 4-pocket model is a spontaneous orbital (nematic) order, followed by s^{+-} superconductivity. In the effective 3-pocket model, orbital fluctuations are weaker, and the system develops either s^{+-} superconductivity or a stripe spin-density wave. In the latter case, nematicity is induced by composite spin fluctuations.

  15. submitter Quench Protection of Very Large, 50-GJ-Class, and High-Temperature-Superconductor-Based Detector Magnets

    CERN Document Server

    Mentink, Matthias; Mulder, Tim; Van Nugteren, Jeroen; ten Kate, Herman

    2016-01-01

    An investigation is performed on the quench behavior of a conceptual 50-GJ 8-T high-temperature-superconductor-based solenoid. In this design, a 50-kA conductor-on-round-core cable-in-conduit conductor utilizing ReBCO technology is envisioned, operating at 40 K. Various properties such as resistivity, thermal conductivity, and heat capacity are very different at this temperature, which affects the quench behavior. It is found that the envisioned conductor is very stable with a minimum quench energy of about 2 kJ. However, the quench propagation velocity is typically about 20 mm/s, so that creating a wide-spread normal zone throughout the coil is very challenging. Moreover, an extraction voltage exceeding 20 kV would be required to ensure a hot-spot temperature below 100 K once a thermal runaway occurs. A novel concept dubbed “rapid quench transformation” is proposed whereby the superconducting conductor is co-wound with a normal conductor to achieve a high degree of inductive coupling. This geometry allow...

  16. Exploring nuclear magnetic resonance at the highest pressure. Closing the pseudogap under pressure in a high temperature superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Meissner, Thomas

    2013-05-13

    In the present work, a novel probe design for high pressure NMR experiments in gem anvil cells (GAC) was used which places a small microcoil inside the high pressure volume as the detection coil. Based on tests carried out at ambient pressure and high pressure of 42 kbar it is demonstrated that this approach is indeed feasible and results in an increase of sensitivity by two orders of magnitude compared to previous GAC-NMR designs. The design was then successfully employed in the investigation of the electronic properties of metallic aluminum and the high temperature superconductor YBa{sub 2}Cu{sub 4}O{sub 8} at pressures of up to 101 kbar. Because of its improved sensitivity and the potential to achieve even higher pressures, the microcoil GAC-NMR setup should prove useful in the investigation of materials under high pressure conditions in the future. In the case of metallic aluminum, the effect of pressure on the electronic density of states at the Fermi level was probed via the Knight-shift K and the spin-lattice relaxation time T{sub 1} at room temperature up to a pressure of 101 kbar, extending the pressure range of previous NMR measurements by a factor of 14 [72]. Most notably, a decrease of K(p) by 11% is detected in the investigated pressure range that is inconsistent with a free electron behavior of the density of states. Numerical band structure calculations that are in excellent agreement with the experimental data suggest that the observed changes of K and T{sub 1} are due to a kink in the electronic states at a Lifshitz-transition at about 75 kbar which has not been observed previously. A further decrease of K by a factor of 2 is predicted to occur in the pressure range up to 300 kbar. In addition, an increase of the NMR linewidths of the metallic aluminum signal was observed above about 42 kbar that is inconsistent with a pure dipolar linewidth. Based on an analysis of the field dependence of this effect it was ascribed to a small additional

  17. Superconductor cable

    Science.gov (United States)

    Allais, Arnaud; Schmidt, Frank (Langenhagen, DE

    2009-12-15

    A superconductor cable includes a superconductive cable core (1) and a cryostat (2) enclosing the same. The cable core (1) has a superconductive conductor (3), an insulation (4) surrounding the same and a shielding (5) surrounding the insulation (4). A layer (3b) of a dielectric or semiconducting material is applied to a central element (3a) formed from a normally conducting material as a strand or tube and a layer (3c) of at least one wire or strip of superconductive material is placed helically on top. The central element (3a) and the layer (3c) are connected to each other in an electrically conducting manner at the ends of the cable core (1).

  18. Energy gap and upper critical field of the new magnetic superconductor Mo{sub 3}Sb{sub 7} found by the Andreev reflection method

    Energy Technology Data Exchange (ETDEWEB)

    Dmitriev, V M [B Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 61103 Kharkiv (Ukraine); Rybaltchenko, L F [B Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 61103 Kharkiv (Ukraine); Ishchenko, L A [B Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 61103 Kharkiv (Ukraine); Khristenko, E V [B Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 61103 Kharkiv (Ukraine); Bukowski, Z [W Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50-950 Wroclaw 2 (Poland); Troc, R [W Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50-950 Wroclaw 2 (Poland)

    2006-06-15

    We present the data of the point contact (PC) Andreev-reflection measurements on the new paramagnetic superconductor Mo{sub 3}Sb{sub 7}, which were used for finding the energy gap {delta} and upper critical field H{sub c2} for this compound. The maximum gap value, reduced to the zero temperature via the Bardeen-Cooper-Schrieffer (BCS) theory, turned out to be {delta} (0) {approx_equal} 0.32 meV, which is slightly smaller than that expected from the BCS theory, {delta}{sup BCS} (0) {approx_equal} 0.35 meV. The temperature dependence of the gap obeys the BCS theory approximately. The H{sub c2}(0) value of about 16.5 kOe was obtained from fitting the experimental data to the conventional H(T) dependence, which is quadratic in temperature. This value is in close agreement with the result from magnetization measurements of 17.2 kOe.

  19. Magnetic field dependence of vortex activation energy: A comparison between MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10 superconductors

    Indian Academy of Sciences (India)

    S D Kaushik; V Braccini; S Patnaik

    2008-12-01

    The dissipative mechanism at low current density is compared in three different classes of superconductors. This is achieved by measuring the resistance as a function of temperature and magnetic field in clean polycrystalline samples of NbSe2, MgB2 and Bi2Sr2Ca2Cu3O10 (BSCCO) superconductors. Thermally activated flux flow behaviour is seen in all the three systems and clearly identified in bulk MgB2. While the activation energy at low fields for MgB2 is comparable to Bi2Sr2Ca2Cu3O10, its field dependence follows a parabolic behaviour unlike a power-law dependence seen in Bi2Sr2Ca2Cu3O10. We analyse our results based on Kramer's scaling for grain boundary pinning in MgB2 and NbSe2.

  20. Chemical spray pyrolysis of Tl-Ba-Ca-Cu-O high-T(sub c) superconductors for high-field bitter magnets

    Science.gov (United States)

    Derochemont, L. Pierre; Zhang, John G.; Squillante, Michael R.; Hermann, A. M.; Duan, H. M.; Andrews, Robert J.; Kelliher, Warren C.

    1991-01-01

    The deposition of Tl-Ba-Ca-Cu-O thick films by spray pyrolyzing a Ba-Ca-Cu-O precursor film and diffusing thallium into the film to form the superconducting phase is examined. This approach was taken to reduce exposure to thallium and its health and safety hazards. The Tl-Ba-Ca-Cu-O system was selected because it has very attractive features which make it appealing to device and manufacturing engineering. Tl-Ba-Ca-Cu-O will accommodate a number of superconducting phases. This attribute makes it very forgiving to stoichiometric fluctuations in the bulk and film. It has excellent thermal and chemical stability, and appears to be relatively insensitive to chemical impurities. Oxygen is tightly bound into the systems, consequently there is no orthorhombic (conductor) to tetragonal (insulator) transition which would affect a component's lifetime. More significantly, the thallium based superconductors appear to have harder magnetic properties than the other high-Tc oxide ceramics. Estimates using magnetoresistance measurements indicate that at 77 K Tl2Ba2CaCu2O10 will have an upper critical field, H(sub c2) fo 26 Tesla for applied fields parallel to the c-axis and approximately 1000 Tesla for fields oriented in the a-b plane. Results to date have shown that superconducting films can be reproducibly deposited on 100 oriented MgO substrates. One film had a zero resistance temperature of 111.5 K. Furthermore, x ray diffraction analysis of the films showed preferential c-axis orientation parallel to the plane of the substrate. These results have now made it possible to consider the manufacture of a superconducting tape wire which can be configured into a topology useful for high-field magnet designs. The research which leads to the preparation of these films and plans for further development are reviewed.

  1. Thermal conductivity and dielectric properties of a TiO2-based electrical insulator for use with high temperature superconductor-based magnets

    Science.gov (United States)

    Ishmael, S. A.; Slomski, M.; Luo, H.; White, M.; Hunt, A.; Mandzy, N.; Muth, J. F.; Nesbit, R.; Paskova, T.; Straka, W.; Schwartz, J.

    2014-09-01

    Quench protection is a remaining challenge impeding the implementation of high temperature superconductor (HTS)-based magnet applications. This is due primarily to the slow normal zone propagation velocity (NZPV) observed in Bi2Sr2CaCu2OX (Bi2212) and (RE)Ba2Cu3O7 - x (REBCO) systems. Recent computational and experimental findings reveal significant improvements in turn-to-turn NZPV, resulting in a magnet that is more stable and easier to protect through three-dimensional normal zone growth (Phillips M 2009; Ishmael S et al 2013 IEEE Trans. Appl. Supercond. 23 7201311). These improvements are achieved by replacing conventional insulation materials, such as Kapton and mullite braid, with a thin, thermally conducting, electrically-insulating ceramic oxide coating. This paper reports on the temperature-dependent thermal properties, electrical breakdown limits and microstructural characteristics of a titanium oxide (TiO2) insulation and a doped-TiO2-based proprietary insulation (doped-TiO2) shown previously to enhance quench behavior (Ishmael S et al 2013 IEEE Trans. Appl. Supercond. 23 7201311). Breakdown voltages at 77 K ranging from ˜1.5 kV to over 5 kV are reported. At 4.2 K, the TiO2 increases the thermal conductivity of polyimide by about a factor of 10. With the addition of a dopant, thermal conductivity is increased by an additional 13%, and a high temperature heat treatment increases it by nearly an additional 100%. Similar increases are observed at 77 K and room temperature. These results are understood in the context of the various microstructures observed.

  2. Exploring nuclear magnetic resonance at the highest pressure. Closing the pseudogap under pressure in a high temperature superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Meissner, Thomas

    2013-05-13

    In the present work, a novel probe design for high pressure NMR experiments in gem anvil cells (GAC) was used which places a small microcoil inside the high pressure volume as the detection coil. Based on tests carried out at ambient pressure and high pressure of 42 kbar it is demonstrated that this approach is indeed feasible and results in an increase of sensitivity by two orders of magnitude compared to previous GAC-NMR designs. The design was then successfully employed in the investigation of the electronic properties of metallic aluminum and the high temperature superconductor YBa{sub 2}Cu{sub 4}O{sub 8} at pressures of up to 101 kbar. Because of its improved sensitivity and the potential to achieve even higher pressures, the microcoil GAC-NMR setup should prove useful in the investigation of materials under high pressure conditions in the future. In the case of metallic aluminum, the effect of pressure on the electronic density of states at the Fermi level was probed via the Knight-shift K and the spin-lattice relaxation time T{sub 1} at room temperature up to a pressure of 101 kbar, extending the pressure range of previous NMR measurements by a factor of 14 [72]. Most notably, a decrease of K(p) by 11% is detected in the investigated pressure range that is inconsistent with a free electron behavior of the density of states. Numerical band structure calculations that are in excellent agreement with the experimental data suggest that the observed changes of K and T{sub 1} are due to a kink in the electronic states at a Lifshitz-transition at about 75 kbar which has not been observed previously. A further decrease of K by a factor of 2 is predicted to occur in the pressure range up to 300 kbar. In addition, an increase of the NMR linewidths of the metallic aluminum signal was observed above about 42 kbar that is inconsistent with a pure dipolar linewidth. Based on an analysis of the field dependence of this effect it was ascribed to a small additional

  3. Flux pinning in superconductors

    CERN Document Server

    Matsushita, Teruo

    2014-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  4. Flux Pinning in Superconductors

    CERN Document Server

    Matsushita, Teruo

    2007-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  5. Superconductor bearings, flywheels and transportation

    Science.gov (United States)

    Werfel, F. N.; Floegel-Delor, U.; Rothfeld, R.; Riedel, T.; Goebel, B.; Wippich, D.; Schirrmeister, P.

    2012-01-01

    This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS-FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

  6. Persistent trigeminal artery: angio-tomography and angio-magnetic resonance finding

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Licia Pacheco; Nepomuceno, Lara A.M.; Coimbra, Pablo Picasso; Oliveira Neto, Sabino Rodrigues de [Hospital Geral de Fortaleza (HGF), CE (Brazil). Radiology Dept.], e-mail: licia_p@hotmail.com; Natal, Marcelo Ricardo C. [Hospital de Base do Distrito Federal, Brasilia, DF (Brazil)

    2009-09-15

    The trigeminal artery (TA) is the most common embryonic carotid-vertebrobasilar anastomosis to persist into adulthood. It typically extends from the internal carotid artery to the basilar artery. Persistent primitive arteries are usually found incidentally, but are often associated with vascular malformation, cerebral aneurysm and, in case of TA, with trigeminal neuralgia. We present one patient with TA as a cause of trigeminal neuralgia and in other three as an incidental finding, on TC and MR angiograms. (author)

  7. High-temperature superconductors

    CERN Document Server

    Saxena, Ajay Kumar

    2010-01-01

    The present book aims at describing the phenomenon of superconductivity and high-temperature superconductors discovered by Bednorz and Muller in 1986. The book covers the superconductivity phenomenon, structure of high-Tc superconductors, critical currents, synthesis routes for high Tc materials, superconductivity in cuprates, the proximity effect and SQUIDs, theories of superconductivity and applications of superconductors.

  8. Effects of chiral helimagnets on vortex states in a superconductor

    Science.gov (United States)

    Fukui, Saoto; Kato, Masaru; Togawa, Yoshihiko

    2016-12-01

    We have investigated vortex states in chiral helimagnet/superconductor bilayer systems under an applied external magnetic field {H}{appl}, using the Ginzburg-Landau equations. Effect of the chiral helimagnet on the superconductor is taken as a magnetic field {H}{CHM}, which is perpendicular to the superconductor and oscillates spatially. For {H}{appl}=0 and weak {H}{CHM}, there appear pairs of up- and down-vortices. Increasing {H}{appl}, down-vortices gradually disappear, and the number of up-vortices increases in the large magnetic field region. Then, up-vortices form parallel, triangular, or square structures.

  9. Manufacturing of Superconductors

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Bay, Niels

    Superconducting tapes based on the ceramic high temperature superconductor (HTS) is a new promising product for high current applications such as electro-magnets and current transmission cables. The tapes are made by the oxide powder in tube (OPIT) method implying drawing and rolling of silver...... on the mechanical and thermal processes applied. One of the most crucial processes is probably the flat rolling process, where the round or square wire is rolled to form a thin tape (about 3 mm x 0.2 mm), while the density of the powder fibres increase and the fibres obtain their final geometry. For instance...... rolling a tape to a thickness of 250 µm may give a very high Je, whereas further reduction to 200 µm may be fatal. In the present work the flat rolling process is analysed systematically from a mechanical forming point of view. This work implies · Mechanical characterisation of the plastic parameters...

  10. Atrial and ventricular volume and function in persistent and permanent atrial fibrillation, a magnetic resonance imaging study

    DEFF Research Database (Denmark)

    Therkelsen, Susette Krohn; Groenning, Bjoern Aaris; Svendsen, Jesper Hastrup

    2005-01-01

    Left atrial size is independently related to cardiovascular morbidity and mortality, and atrial fibrillation (AF) is strongly associated with atrial size. Our aims were to report atrial and ventricular dimensions in patients with AF evaluated with magnetic resonance imaging (MRI), and to assess...... the inter-study reproducibility of the measurements. Nineteen healthy volunteers, 19 patients with permanent AF, and 58 patients with persistent AF had cardiac dimensions evaluated by 6-mm cinematographic breath-hold MRI scans using a 1.5 Tesla Siemens Vision Magnetom scanner with a phased array chest coil...

  11. Aluminum-stabilized NB3SN superconductor

    Science.gov (United States)

    Scanlan, Ronald M.

    1988-01-01

    An aluminum-stabilized Nb.sub.3 Sn superconductor and process for producing same, utilizing ultrapure aluminum. Ductile components are co-drawn with aluminum to produce a conductor suitable for winding magnets. After winding, the conductor is heated to convert it to the brittle Nb.sub.3 Sn superconductor phase, using a temperature high enough to perform the transformation but still below the melting point of the aluminum. This results in reaction of substantially all of the niobium, while providing stabilization and react-in-place features which are beneficial in the fabrication of magnets utilizing superconducting materials.

  12. Magnetic irreversibility and pinning force density in the Mo{sub 100−x}Re{sub x} alloy superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sundar, Shyam [Homi Bhabha National Institute, Raja Ramanna Center for Advanced Technology, Indore 452 013 (India); Magnetic & Superconducting Materials Section, Raja Ramanna Center for Advanced Technology, Indore 452 013 (India); Chattopadhyay, M.K., E-mail: maulindu@rrcat.gov.in [Homi Bhabha National Institute, Raja Ramanna Center for Advanced Technology, Indore 452 013 (India); Magnetic & Superconducting Materials Section, Raja Ramanna Center for Advanced Technology, Indore 452 013 (India); Sharath Chandra, L.S. [Magnetic & Superconducting Materials Section, Raja Ramanna Center for Advanced Technology, Indore 452 013 (India); Roy, S.B. [Homi Bhabha National Institute, Raja Ramanna Center for Advanced Technology, Indore 452 013 (India); Magnetic & Superconducting Materials Section, Raja Ramanna Center for Advanced Technology, Indore 452 013 (India)

    2015-12-15

    Highlights: • We have studied the critical current and pinning force in the Mo{sub 100−x}Re{sub x} (15 ⩽ x ⩽ 48) alloys. • Dislocation networks and point defects are found to pin the flux lines in intermediate fields. • In high fields, the critical current density is affected by flux creep. • In low fields the pinning is influenced by the presence of two superconducting energy gaps. • The double gap also contributes to the asymmetry observed in the M–H hysteresis loops. - Abstract: We have measured the isothermal field dependence of magnetization of the Mo{sub 100−x}Re{sub x} (15 ⩽ x ⩽ 48) alloys, and have estimated the critical current and pinning force density from these measurements. We have performed structural characterization of the above alloys using standard techniques, and analyzed the field dependence of critical current and pinning force density using existing theories. Our results indicate that dislocation networks and point defects like voids and interstitial imperfections are the main flux line pinning centers in the Mo{sub 100−x}Re{sub x} alloys in the intermediate fields, i.e., in the “small bundle” flux line pinning regime. In this regime, the critical current density is also quite robust against increasing magnetic field. In still higher fields, the critical current density is affected by flux creep. In the low field regime, on the other hand, the pinning of the flux lines seems to be influenced by the presence of two superconducting energy gaps in the Mo{sub 100−x}Re{sub x} alloys. This modifies the field dependence of critical current density, and also seems to contribute to the asymmetry in the magnetic irreversibility exhibited by the isothermal field dependence of magnetization.

  13. Magnetic-field-induced charge-stripe order in the high-temperature superconductor YBa2Cu3Oy.

    Science.gov (United States)

    Wu, Tao; Mayaffre, Hadrien; Krämer, Steffen; Horvatić, Mladen; Berthier, Claude; Hardy, W N; Liang, Ruixing; Bonn, D A; Julien, Marc-Henri

    2011-09-07

    Electronic charges introduced in copper-oxide (CuO(2)) planes generate high-transition-temperature (T(c)) superconductivity but, under special circumstances, they can also order into filaments called stripes. Whether an underlying tendency towards charge order is present in all copper oxides and whether this has any relationship with superconductivity are, however, two highly controversial issues. To uncover underlying electronic order, magnetic fields strong enough to destabilize superconductivity can be used. Such experiments, including quantum oscillations in YBa(2)Cu(3)O(y) (an extremely clean copper oxide in which charge order has not until now been observed) have suggested that superconductivity competes with spin, rather than charge, order. Here we report nuclear magnetic resonance measurements showing that high magnetic fields actually induce charge order, without spin order, in the CuO(2) planes of YBa(2)Cu(3)O(y). The observed static, unidirectional, modulation of the charge density breaks translational symmetry, thus explaining quantum oscillation results, and we argue that it is most probably the same 4a-periodic modulation as in stripe-ordered copper oxides. That it develops only when superconductivity fades away and near the same 1/8 hole doping as in La(2-x)Ba(x)CuO(4) (ref. 1) suggests that charge order, although visibly pinned by CuO chains in YBa(2)Cu(3)O(y), is an intrinsic propensity of the superconducting planes of high-T(c) copper oxides.

  14. Anisotropic Field Dependence of the Superconducting Transition in the Magnetic Molecular Superconductor κ-(BETS)2FeBr4

    Science.gov (United States)

    Fukuoka, Shuhei; Yamashita, Satoshi; Nakazawa, Yasuhiro; Yamamoto, Takashi; Fujiwara, Hideki

    2017-01-01

    Angle-resolved heat capacity measurements of a π-d interacting system of κ-(BETS)2FeBr4 [BETS = bis(ethylenedithio)tetraselenafulvalene] with in-plane magnetic fields are performed. We observed a thermal anomaly in association with the superconducting transition of the π electrons in the π-d compound for the first time. By pursuing a systematic change in the thermal anomaly, we found that the thermodynamic feature of the superconducting state shows large anisotropy against in-plane magnetic fields. When the field is applied parallel to the c-axis, the thermal anomaly remains up to 2.6 T with a distinct peak structure. On the other hand, it is suppressed in synchrony with the decrease of the antiferromagnetic transition temperature, when the field is applied parallel to the a-axis. Our thermodynamic results indicate that the effect of the π-d interaction appears even when the π electrons are itinerant and that the anisotropic field-direction dependence of the superconducting transition originates from the correlation between superconductivity and magnetism.

  15. Spray-Deposited Superconductor/Polymer Coatings

    Science.gov (United States)

    Wise, Stephanie A.; Tran, Sang Q.; Hooker, Matthew W.

    1993-01-01

    Coatings that exhibit the Meissner effect formed at relatively low temperature. High-temperature-superconductor/polymer coatings that exhibit Meissner effect deposited onto components in variety of shapes and materials. Simple, readily available equipment needed in coating process, mean coatings produced economically. Coatings used to keep magnetic fields away from electronic circuits in such cryogenic applications as magnetic resonance imaging and detection of infrared, and in magnetic suspensions to provide levitation and/or damping of vibrations.

  16. Is the Long-Term Persistency of Circular Polarisation due to the Constant Helicity of the Magnetic Fields in Rotating Quasar Engines?

    OpenAIRE

    Ensslin, Torsten A.

    2003-01-01

    Many compact radio sources like quasars, blazars, radio galaxies, and micro-quasars emit circular polarisation (CP) with surprising temporal persistent handedness. We propose that the CP is caused by Faraday conversion of linear polarisation synchrotron light which propagates along a line-of-sight through helical magnetic fields. Jet outflows from radio galaxies should have the required magnetic helicity in the emission region due to the magnetic torque of the accretion disc. Also advection d...

  17. Magnetic Flux-Trapping of Anisotropic-Grown Y-Ba-Cu-O Bulk Superconductors during and after Pulsed-Field Magnetizing Processes

    Science.gov (United States)

    Oka, T.; Yamada, Y.; Horiuchi, T.; Ogawa, J.; Fukui, S.; Sato, T.; Yokoyama, K.; Langer, M.

    2014-05-01

    The magnetic flux penetration into the melt-textured Y-Ba-Cu-O high temperature superconducting bulk magnets were precisely evaluated during and after the pulsed field magnetization processes operated at 30 K. The bulk magnets were carefully fabricated by the cold seeding method with use of a single and a pair of seed crystals composed of the Nd-Ba-Cu-O thin films. These seed crystals were put on the top surfaces of the precursors to let the large grains grow during the heat treatments. We observed the flux penetrations which occurred in the lower applied-field regions at around 3.1 T for the samples bearing the twin seeds than those of the single-seeded crystals at around 3.8 T. This means that the magnetic fluxes are capable of invading into the twin-seeded samples more easily than the single-seeds. It suggests that the anisotropic grain growths of parallel and normal to the rows of seed crystals affects the variations of Jc values with different distributions of the pinning centers, results in the preferential paths for the invading magnetic fluxes.

  18. Persistence of magnetic field driven by relativistic electrons in a plasma

    CERN Document Server

    Flacco, A; Lifschitz, A; Sylla, F; Kahaly, S; Veltcheva, M; Silva, L O; Malka, V

    2015-01-01

    The onset and evolution of magnetic fields in laboratory and astrophysical plasmas is determined by several mechanisms, including instabilities, dynamo effects and ultra-high energy particle flows through gas, plasma and interstellar-media. These processes are relevant over a wide range of conditions, from cosmic ray acceleration and gamma ray bursts to nuclear fusion in stars. The disparate temporal and spatial scales where each operates can be reconciled by scaling parameters that enable to recreate astrophysical conditions in the laboratory. Here we unveil a new mechanism by which the flow of ultra-energetic particles can strongly magnetize the boundary between the plasma and the non-ionized gas to magnetic fields up to 10-100 Tesla (micro Tesla in astrophysical conditions). The physics is observed from the first time-resolved large scale magnetic field measurements obtained in a laser wakefield accelerator. Particle-in-cell simulations capturing the global plasma and field dynamics over the full plasma le...

  19. On n-quantum vortices in superconductors

    CERN Document Server

    Marchenko, V I

    2002-01-01

    The conditions of the n-quantum vortices observation in the superconductors are discussed. It is established in the course of calculating the coefficient by the |psi| sup 6 (psi - the order parameter) in the Ginzburg-Landau theory for the BCS standard model that the sign of this coefficient is negative. This favours the possibility of observing the n-quantum vortices in the superconductors, wherein the vortex lattice with gravitation is formed. The existence of gravitation is manifested in the magnetization finite jump in the H sub 0 = H sub c sub sup 1 field. When by the temperature change the superconductor behavior changes in such a way, that its magnetization in the H sub 0 = H sub c field reduces to the zero, than the observation of the n-quantum vortices near this transition is possible

  20. AC susceptibilities of grain-textured superconductors

    Science.gov (United States)

    Sakamoto, N.; Fukuda, Y.; Koga, M.; Akune, T.; Khan, H. R.; Lüders, K.

    2008-09-01

    In-phase χ n‧ and out-phase χ n″ components of nth harmonics of AC susceptibility with measuring parameters of a DC magnetic field Bdc, an amplitude Ba and a frequency f of the superimposed AC magnetic fields give substantial information of the superconducting properties. In low- Tc metallic superconductors, χ1‧ shows smooth transition and χ1″ does single peak. High- Tc oxide superconductors with anisotropic and grain-textured structures show deformed complex characteristics. Double peaks in χ1″ and shoulders in χ1‧ appear in AC susceptibility of Hg-1223 superconductors. Instead of simple Bean model, a grained model, where the superconducting grains are immersed in weak superconducting matrix, are proposed. The susceptibilities numerically analyzed using the model show varied and deformed curves and are successfully compared with the measured results.

  1. High-temperature superconductor applications development at Argonne National Laboratory

    Science.gov (United States)

    Hull, J. R.; Poeppel, R. B.

    1992-02-01

    Developments at Argonne National Laboratory of near and intermediate term applications using high-temperature superconductors are discussed. Near-term applications of liquid-nitrogen depth sensors, current leads, and magnetic bearings are discussed in detail.

  2. Theoretical studies of unconventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Groensleth, Martin Sigurd

    2008-07-01

    This thesis presents four research papers. In the first three papers we have derived analytical results for the transport properties in unconventional superconductors and ferromagnetic systems with multiple broken symmetries. In Paper I and parts of Paper II we have studied tunneling transport between two non-unitary ferromagnetic spin-triplet superconductors, and found a novel interplay between ferromagnetism and superconductivity manifested in the Josephson effect as a spin- and charge-current in the absence of an applied voltage across the junction. The critical amplitudes of these currents can be adjusted by the relative magnetization direction on each side of the junction. Furthermore, in Paper II, we have found a way of controlling a spin-current between two ferromagnets with spin-orbit coupling. Paper III considers a junction consisting of a ferromagnet and a non-unitary ferromagnetic superconductor, and we show that the conductance spectra contains detailed information about the superconducting gaps and pairing symmetry of the Cooper-pairs. In the last paper we present a Monte Carlo study of an effective Hamiltonian describing orbital currents in the CuO2 layers of high-temperature superconductive cuprates. The model features two intrinsically anisotropic Ising models, coupled through an anisotropic next-nearest neighbor interaction, and an Ashkin-Teller nearest neighbor fourth order coupling. We have studied the specific heat anomaly, as well as the anomaly in the staggered magnetization associated with the orbital currents and its susceptibility. We have found that in a limited parameter regime, the specific heat anomaly is substantially suppressed, while the susceptibility has a non-analytical peak across the order-disorder transition. The model is therefore a candidate for describing the breakup of hidden order when crossing the pseudo-gap line on the under-doped side in the phase diagram of high-temperature superconductors. (Author) 64 refs., figs

  3. Influence of the magnetic field orientation on the mixed state properties of high temperature superconductors: an ac shielding study

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, B

    1999-07-01

    This work deals with the influence of the orientation of an applied static magnetic field on the mixed state properties of high temperature superconducting cuprates. The mixed state is characterized by the presence of vortices (quanta of magnetic flux). Their properties have been tested via the dynamic approach of the shielding of an ac magnetic field. In pristine Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} crystals the first order transition of the vortex system from an ordered to a disordered state has been studied. It has been found that in the material the transition is mainly determined by the component of the field perpendicular to the superconducting copper oxide layers. However, the value of this component at the transition diminishes with the increase of the field component parallel to the layers. This is explained by the decrease of the Josephson coupling between 2D vortices in neighbouring planes in the presence of a parallel component. In heavy ion irradiated Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} the subject under investigation has been the pinning of the vortices by the irradiation tracks. These defects push the irreversibility line towards higher fields. In the field range that has become irreversible after irradiation pinning by columnar defects is anisotropic. This anisotropy in pinning indicates that a coupling exists between the 2D vortices that form a vortex line, in contrast to the behaviour in the pristine material in the same field range. HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8} with columnar defects shows essentially the same behaviour as Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, the differences being well explained by the lower anisotropy of HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8} which leads to a more linear character of the vortices. Finally, it has been shown that in pristine Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} the concentration of the vortices in the center of the sample is explained by the surface barrier alone. (author)

  4. Persistent-current switch for pancake coils of rare earth-barium-copper-oxide high-temperature superconductor: Design and test results of a double-pancake coil operated in liquid nitrogen (77-65 K) and in solid nitrogen (60-57 K)

    Science.gov (United States)

    Qu, Timing; Michael, Philip C.; Voccio, John; Bascuñán, Juan; Hahn, Seungyong; Iwasa, Yukikazu

    2016-08-01

    We present design and test results of a superconducting persistent current switch (PCS) for pancake coils of rare-earth-barium-copper-oxide, REBCO, high-temperature superconductor (HTS). Here, a REBCO double-pancake (DP) coil, 152-mm ID, 168-mm OD, 12-mm high, was wound with a no-insulation technique. We converted a ˜10-cm long section in the outermost layer of each pancake to a PCS. The DP coil was operated in liquid nitrogen (77-65 K) and in solid nitrogen (60-57 K). Over the operating temperature ranges of this experiment, the normal-state PCS enabled the DP coil to be energized; thereupon, the PCS resumed the superconducting state and the DP coil field decayed with a time constant of 100 h, which would have been nearly infinite, i.e., persistent-mode operation, were the joint across the coil terminals superconducting.

  5. Persistent-current switch for pancake coils of rare earth-barium-copper-oxide high-temperature superconductor: Design and test results of a double-pancake coil operated in liquid nitrogen (77–65 K) and in solid nitrogen (60–57 K)

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Timing; Michael, Philip C.; Bascuñán, Juan; Iwasa, Yukikazu, E-mail: iwasa@jokaku.mit.edu [Francis Bitter Magnet Laboratory, Plasma Science and Fusion Center, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139 (United States); Voccio, John [Wentworth Institute of Technology, 550 Huntington Ave, Boston, Massachusetts 02115 (United States); Hahn, Seungyong [National High Magnetic Field Laboratory, Florida State University, Tallahassee, 2031 Paul Dirac Drive, Florida 32310 (United States)

    2016-08-22

    We present design and test results of a superconducting persistent current switch (PCS) for pancake coils of rare-earth-barium-copper-oxide, REBCO, high-temperature superconductor (HTS). Here, a REBCO double-pancake (DP) coil, 152-mm ID, 168-mm OD, 12-mm high, was wound with a no-insulation technique. We converted a ∼10-cm long section in the outermost layer of each pancake to a PCS. The DP coil was operated in liquid nitrogen (77–65 K) and in solid nitrogen (60–57 K). Over the operating temperature ranges of this experiment, the normal-state PCS enabled the DP coil to be energized; thereupon, the PCS resumed the superconducting state and the DP coil field decayed with a time constant of 100 h, which would have been nearly infinite, i.e., persistent-mode operation, were the joint across the coil terminals superconducting.

  6. Giant supercurrent states in a superconductor-InAs/GaSb-superconductor junction

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Xiaoyan, E-mail: xshi@sandia.gov; Pan, W.; Hawkins, S. D.; Klem, J. F. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Yu, Wenlong; Jiang, Zhigang [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Andrei Bernevig, B. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)

    2015-10-07

    Superconductivity in topological materials has attracted a great deal of interest in both electron physics and material sciences since the theoretical predictions that Majorana fermions can be realized in topological superconductors. Topological superconductivity could be realized in a type II, band-inverted, InAs/GaSb quantum well if it is in proximity to a conventional superconductor. Here, we report observations of the proximity effect induced giant supercurrent states in an InAs/GaSb bilayer system that is sandwiched between two superconducting tantalum electrodes to form a superconductor-InAs/GaSb-superconductor junction. Electron transport results show that the supercurrent states can be preserved in a surprisingly large temperature-magnetic field (T – H) parameter space. In addition, the evolution of differential resistance in T and H reveals an interesting superconducting gap structure.

  7. An HTS flux pump operated by directly driving a superconductor into flux flow region in the E- J curve

    Science.gov (United States)

    Geng, Jianzhao; Coombs, T. A.

    2016-09-01

    High-T c superconducting (HTS) flux pumps are capable of compensating the persistent current decay in HTS magnets without electrical contact. In this paper, following work on a low-T c superconducting self-switching flux pump, we propose a new HTS flux pump by directly driving a high-T c superconductor into the flux flow region in the E- J curve. The flux pump consists of a transformer which has a superconducting secondary winding shorted by an YBCO-coated conductor bridge. A high alternating current with a much higher positive peak value than the negative peak value is induced in the secondary winding. The current always drives the bridge superconductor into the flux flow region only at around its positive peak value, thus resulting in flux pumping. The proposed flux pump is much simpler than existing HTS flux pumps.

  8. Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: I. Ag/Bi2Sr2CaCu2Ox multifilament round wires

    Science.gov (United States)

    Ye, Liyang; Li, Pei; Jaroszynski, Jan; Schwartz, Justin; Shen, Tengming

    2017-02-01

    The critical current of many practical superconductors is sensitive to strain, and this sensitivity is exacerbated during a quench that induces a peak local strain which can be fatal to superconducting magnets. Here, a new method is introduced to quantify the influence of the conductor stress and strain state during normal operation on the margin to degradation during a quench, as measured by the maximum allowable hot spot temperature T allowable, for composite wires within superconducting magnets. The first conductor examined is Ag-sheathed Bi2Sr2CaCu2Ox round wire carrying high engineering critical current density, J E, of 550 A mm-2 at 4.2 K and 15 T. The critical axial tensile stress of this conductor is determined to be 150 MPa and, in the absence of Lorentz forces, T allowable is greater than 450 K. With increasing axial tensile stress, σ a, however, T allowable decreases nonlinearly, dropping to 280 K for σ a = 120 MPa and to 160 K for σ a = 145 MPa. T allowable(σ a) is shown to be nonlinear and independent of magnetic field from 15 to 30 T. T allowable(σ a) dictates the balance between magnetic field generation, which increases with the magnet operating current and stress, and the safety margin, which decreases with decreasing T allowable, and therefore has important engineering value. It is also shown that T allowable(σ a) can be predicted accurately by a general strain model, showing that strain control is the key to preventing degradation of superconductors during a quench.

  9. Magnetic neutron scattering resonance of high-¤Tc¤ superconductors in external magnetic fields: An SO(5) study

    DEFF Research Database (Denmark)

    Mortensen, Asger; Rønnow, Henrik Moodysson; Bruus, Henrik

    2000-01-01

    space we find that (i) the scattering amplitude is zero at (pi/a,pi/a), (ii) the resonance peak is split into a ring with radius pi/d centered at (pi/a, pi/a), d being the vortex lattice constant, and consequently, (iii) the splitting pi/d scales with the magnetic field as root B....

  10. Noncontact Measurement Of Critical Current In Superconductor

    Science.gov (United States)

    Israelsson, Ulf E.; Strayer, Donald M.

    1992-01-01

    Critical current measured indirectly via flux-compression technique. Magnetic flux compressed into gap between superconductive hollow cylinder and superconductive rod when rod inserted in hole in cylinder. Hall-effect probe measures flux density before and after compression. Method does not involve any electrical contact with superconductor. Therefore, does not cause resistive heating and consequent premature loss of superconductivity.

  11. Fine uniform filament superconductors

    Science.gov (United States)

    Riley, Jr., Gilbert N.; Li, Qi; Roberts, Peter R.; Antaya, Peter D.; Seuntjens, Jeffrey M.; Hancock, Steven; DeMoranville, Kenneth L.; Christopherson, Craig J.; Garrant, Jennifer H.; Craven, Christopher A.

    2002-01-01

    A multifilamentary superconductor composite having a high fill factor is formed from a plurality of stacked monofilament precursor elements, each of which includes a low density superconductor precursor monofilament. The precursor elements all have substantially the same dimensions and characteristics, and are stacked in a rectilinear configuration and consolidated to provide a multifilamentary precursor composite. The composite is thereafter thermomechanically processed to provide a superconductor composite in which each monofilament is less than about 50 microns thick.

  12. Low Field Scaling of the Flux-Flow Resistivity in the Unconventional Superconductor UPt3

    Science.gov (United States)

    Kambe, S.; Huxley, A. D.; Rodière, P.; Flouquet, J.

    1999-08-01

    Measurements of the flux-flow resistivity in the unconventional superconductor UPt3 are reported for a large range of magnetic field. In agreement with a recent theory, ρf at low field is far larger than that found in conventional superconductors. Its field dependence at different temperatures shows a predicted scaling relation for clean superconductors. The crossover from localized to delocalized quasiparticle excitations around the vortex is also observed as the magnetic field increases.

  13. Remediation of hydrophobic, persistent pollutants using a magnetic permanently confined micelle array (Mag-PCMA)

    Science.gov (United States)

    Clark, K. K.; Keller, A. A.

    2009-12-01

    Natural and anthropogenic factors have resulted in the deposition of hydrophobic organic contaminants (HOCs) like PAHs and PCBs in elevated levels in soils and sediments. Currently there are 150 Superfund sites in the United States with contaminated sediments. Dredging is the most common practice for restoring Superfund sites to their preexisting conditions; this requires the transport of large volumes of material off-site for additional storage or processing. Our lab has designed a nano-hybrid material that can be used on-site; it combines a magnetic nanoscale iron oxide core coated with a cationic surfactant and is encased in a mesoporous silica matrix, called magnetic permanently confined micelle arrays, (Mag-PCMAs). This sorbent has been designed to remove HOCs from such scenarios. Surfactants are important in the enhancement of transport from binding sites in nature, such as organic matter, onto sorbents and other recoverable materials. The sorbent’s magnetic core allows for rapid separation by applying a magnetic field. It has also been shown to be reusable and maintain a removal efficiency of 95% over five cycles of reuse. Preliminary sorption studies show that the sorbent is capable of removing up to 98% of hydrophobic compounds from aqueous media. Current sorption studies are being done to test the efficiency of removing PAHs and PCBs from sediments, soils, and suspended sediments. Physicochemical properties that will influence the desorption/sorption hysteresis are being characterized to determine which properties enhance desorption from the contaminated media onto the Mag-PCMAs. Relevant applications are diverse as this material has the potential to recover a variety of HOCs in both ex situ and in situ remediation scenarios. Magnetic Permanently Confined Micelle Arrays

  14. Superconductor rotor cooling system

    Science.gov (United States)

    Gamble, Bruce B.; Sidi-Yekhlef, Ahmed; Schwall, Robert E.; Driscoll, David I.; Shoykhet, Boris A.

    2002-01-01

    A system for cooling a superconductor device includes a cryocooler located in a stationary reference frame and a closed circulation system external to the cryocooler. The closed circulation system interfaces the stationary reference frame with a rotating reference frame in which the superconductor device is located. A method of cooling a superconductor device includes locating a cryocooler in a stationary reference frame, and transferring heat from a superconductor device located in a rotating reference frame to the cryocooler through a closed circulation system external to the cryocooler. The closed circulation system interfaces the stationary reference frame with the rotating reference frame.

  15. Photothermal measurements of superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kino, G.S.; Studenmund, W.R.; Fishman, I.M. [Stanford Univ., Stanford, CA (United States)

    1996-12-31

    A photothermal technique has been used to measure diffusion and critical temperature in high temperature superconductors. The technique is particularly suitable for determining material quality and inhomogeneity.

  16. X-ray speckle experiments on the persistence and disintegration of magnetic memory

    Science.gov (United States)

    Pierce, Michael Scott

    Beautiful theories based on random microscopic disorder have been developed over the past ten years. My goal was to directly compare these theories with precise experiments. To do so, I first developed and then applied coherent x-ray speckle metrology to a series of thin multilayer perpendicular magnetic materials. To directly observe the effects of disorder, increasing degrees of disorder was deliberately introduced into a series of magnetic films. I used coherent x-rays, produced at the Advanced Light Source at Lawrence Berkeley National Laboratory, to generate highly speckled magnetic scattering patterns. The scattering patterns provided both the ensemble average characteristics of the magnetic domains, but were also directly sensitive to the microscopic magnetic domains. The apparently "random" arrangement of the speckles is due to the exact configuration of the magnetic domains in the sample. In effect, each speckle pattern acts as a unique fingerprint for the magnetic domain configuration. Small changes in the domain structure change the speckles, and comparison of the different speckle patterns provides a quantitative determination of how much the domain structure has changed. My experiments quickly answered one longstanding question: How is the magnetic domain configuration at one point on the major hysteresis loop related to the configurations at the same point on the loop during subsequent cycles? This is called microscopic return point memory (RPM). I found the RPM is partial and imperfect in the disordered samples, and completely absent when the disorder was not present. I also introduced and answered a second important, new question: How are the magnetic domains at one point on the major hysteresis loop related to the domains at the complementary point, the inversion symmetric point on the loop, during the same and during subsequent cycles? This is called microscopic complementary point memory (CPM). I found the CPM is also partial and imperfect in the

  17. Zeroth Order Phase Transition in a Holographic Superconductor with Single Impurity

    CERN Document Server

    Zeng, Hua Bi

    2014-01-01

    We studied the single normal impurity effect in superconductor by using the holographic method. When the size of impurity is much smaller compared to the host superconductor, we reproduced the Anderson theorem, which states that a conventional s-wave superconductor is robust to a normal (non-magnetic) impurity with small impurity strength or impurities with small concentration. While by increasing the size of impurity in a fixed host superconductor we also find a decrease $T_c$ of the host superconductor, the phase transition at the critical impurity strength is of zeroth order.

  18. Circulating persistent current and induced magnetic field in a fractal network

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Srilekha [Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Sector-I, Block-AF, Bidhannagar, Kolkata 700 064 (India); Maiti, Santanu K., E-mail: santanu.maiti@isical.ac.in [Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata 700 108 (India); Karmakar, S.N. [Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Sector-I, Block-AF, Bidhannagar, Kolkata 700 064 (India)

    2016-04-29

    We present the overall conductance as well as the circulating currents in individual loops of a Sierpinski gasket (SPG) as we apply bias voltage via the side attached electrodes. SPG being a self-similar structure, its manifestation on loop currents and magnetic fields is examined in various generations of this fractal and it has been observed that for a given configuration of the electrodes, the physical quantities exhibit certain regularity as we go from one generation to another. Also a notable feature is the introduction of anisotropy in hopping causes an increase in magnitude of overall transport current. These features are a subject of interest in this article. - Highlights: • Voltage driven circular current is analyzed in a fractal network. • Current induced magnetic field is strong enough to flip a spin. • Anisotropy in hopping enhances overall transport current.

  19. Temperature dependence of the upper critical field of high- Tc superconductors from isothermal magnetization data: influence of a temperature dependent Ginzburg-Landau parameter

    Science.gov (United States)

    Landau, I. L.; Ott, H. R.

    2003-11-01

    We show that the scaling procedure, recently proposed for the evaluation of the temperature variation of the normalized upper critical field of type-II superconductors, may easily be modified in order to take into account a possible temperature dependence of the Ginzburg-Landau parameter κ. As an example we consider κ( T) as it follows from the microscopic theory of superconductivity.

  20. Application of High Temperature Superconductors to Accelerators

    CERN Document Server

    Ballarino, A

    2000-01-01

    Since the discovery of high temperature superconductivity, a large effort has been made by the scientific community to investigate this field towards a possible application of the new oxide superconductors to different devices like SMES, magnetic bearings, flywheels energy storage, magnetic shielding, transmission cables, fault current limiters, etc. However, all present day large scale applications using superconductivity in accelerator technology are based on conventional materials operating at liquid helium temperatures. Poor mechanical properties, low critical current density and sensitivity to the magnetic field at high temperature are the key parameters whose improvement is essential for a large scale application of high temperature superconductors to such devices. Current leads, used for transferring currents from the power converters, working at room temperature, into the liquid helium environment, where the magnets are operating, represent an immediate application of the emerging technology of high t...