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Author (up) Luzuriaga, J.; Andre, M.-O.; Benoit, W.
Title Frequency and amplitude response of the flux-line lattice to mechanical perturbation in ceramic YBa2Cu3O7 Type Journal Article
Year 1992 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 201 Issue 3-4 Pages 257-262
Keywords Copper oxides; Crystal lattices; Frequency response; Internal friction; Lattice vibrations; Magnetic fields; Mathematical models; Mechanical properties; Pendulums; Rheology; Thermal effects; Torque; Yttrium compounds; Amplitude response; Ceramic yttrium barium copper oxides; Extended dry friction model; Flux line lattices; Forced pendulum; Frequency independent dissipation peak; Mechanical response; Thermal activation; High temperature superconductors
Abstract The mechanical response of the flux-line lattice has been measured with a low-frequency forced pendulum in ceramic YBa2Cu3O7. A dissipation peak observed in temperature sweeps is frequency-independent between 1 mHz and 5 Hz. Dissipation depends strongly on applied torque, and for fixed temperatures this dependence is well fitted by a rheological model of extended dry friction. If the model is extended to take account of thermal activation, however, it does not agree with the measured frequency independence, which is hard to explain within simple models of thermal activation.
Address Institut de G
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Notes Export Date: 28 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Luzuriaga, J.; Institut de G Approved no
Call Number BT @ luzuriag @ Serial 487
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Author (up) Martin, J.I.; Wuyts, B.; Maenhoudt, M.; Osquiguil, E.; Vicent, J.L.; Moshchalkov, V.V.; Bruynseraede, Y.
Title Sign reversal of the flux flow Hall effect in oxygen deficient YBa2Cu3Ox films Type Journal Article
Year 1994 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 2 Pages 1451-1452
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Abstract The Hall effect of high temperature superconductors has been reported to slow in some cases a striking sign reversal near Tc, the origin of which is not yet fully understood. We report on measurements of the Hall effect in the mixed state of oxygen deficient YBa2Cu3Ox thin films, for 7?
Address Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Martin, J.I.; Dpto. Fisica de Materiales; Facultad de Ciencias Fisicas; Universidad Complutense 28040 Madrid, Spain Approved no
Call Number BT @ osquigui @ Serial 386
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Author (up) Massa, N. E.; Rasines, I.; Nieva, G.; Campá, J. A.; Fainstein, C.
Title Far infrared transmission spectra of Bi2Sr2Ca1(Cu1−x,Znx)2O8+δ, 0.0≤x≤0.05, crystallites in the normal state: Detection of superconducting gap precursors Type Journal Article
Year 1994 Publication Physica C: Superconductivity Abbreviated Journal Physica C
Volume 235-240 Issue 2 Pages 1065-1066
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Abstract We report transmission spectra of crystallites, taken from single crystal specimens of two plane Bi2Sr2Ca1(Cu1−x,Znx)2O8+δ, 0.0≤x≤0.05, diluted in CsI or polyethylene matrices In addition to weaker features assigned to unscreened phonons and a continuous background probably due to carriers, we found that the ratios of room temperature spectra to those taken lowering the temperature in 50 degrees intervals signal the presence of superconducting gap behavior with 2Δ/kBTc6. We verified this by down shifting frequency as a function of Zn increment and the lowering of Tc induced by this strong superconductivity suppressor. Our preliminary search for phonons self-energy effects close to the superconducting transition temperature gave negative results.
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Call Number BT @ gnieva @ Serial 452
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Author (up) Nakamura, O.; Fullerton, E.E.; Guimpel, J.; Schuller, I.K.
Title Disorder and superconductivity in YBa2Cu3O7−δ/GdBa2Cu3O7-δ superlattices Type Journal Article
Year 1991 Publication Physica C: Superconductivity Abbreviated Journal
Volume 185-189, Part 3 Issue Pages 2069-2070
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Abstract The structure of coriented YBa2Cu3O7−δ/GdBa2Cu3O7−δ superlattices is analyzed throug refinement of the X-ray diffraction spectrum. This novel technique, similar in spirit to the well known Rietveld refinement of powder X-ray diffraction spectra, allows quantitative determination of the interfacial roughness. The results show that for these superlattices the roughness consists in step disorder of one unit cell around the average thickness of the layer and interdiffusion of 15 to 25% between the Y and Gd sites within one unit cell from the interface.
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Call Number BT @ jguimpel @ Serial 617
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Author (up) Navarro, H.; Sirena, M.; Kim, J.; Haberkorn, N.
Title Smooth surfaces in very thin GdBa2Cu3O7−δ films for application in superconducting tunnel junctions Type Journal Article
Year 2015 Publication Physica C: Superconductivity and its Applications Abbreviated Journal Physica C
Volume 510 Issue Pages 21-26
Keywords Thin films; Superconductivity; Morphology
Abstract Abstract

This paper provides a systematic analysis of the morphology and the superconducting critical temperature obtained in very thin GdBa2Cu3O7−δ films grown on (0 0 1) SrTiO3 substrates by DC sputtering. We find that the use of a very thin SrTiO3 buffer layer (≈2 nm) modify the nucleation of GdBa2Cu3O7−δ on the surface of the substrate reducing the formation of 3 dimensional clusters. Our results demonstrate that 16 nm thick GdBa2Cu3O7−δ films with an average root-mean-square (RMS) smaller than 1 nm and large surface areas (up 10 μm2) free of 3 dimensional topological defects can be obtained. In films thinner than 24 nm the onset (zero resistance) of superconducting transition of the films is reduced, being close to liquid nitrogen. This fact can be associated with stress reducing the orthorhombicity and slightly drop in oxygen stoichiometry.
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Call Number BT @ pedrazp @ Serial 726
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Author (up) Núñez Regueiro, M.; Esquinazi, P.; Izbizky, M.A.; Duran, C.; Castello, D.; Luzuriaga, J.; Nieva, G.
Title Evidence of tunneling systems through thermal and acoustic measurements in ceramic materials Type Journal Article
Year 1988 Publication Physica C: Superconductivity and its applications Abbreviated Journal Physica C
Volume 153-155 Issue PART 2 Pages 1016-1017
Keywords Acoustic Variables Measurement--Wave Velocity; Ceramic Materials--Thermal Conductivity; Europium Barium Copper Oxides; Superconducting Materials
Abstract We have neasured the sound velocity, internal friction, thermal conductivity and specific heat of La-based and (Y/Eu)- based ceramics. The low temperature data can be understood in terms of the Tunneling Model assuming the existence of Tunneling Systems (TS). From these measured properties we obtain values for the parameter C=P?2/?v2, where P is the density of states of TS, ? the coupling constant between phonons and TS, ? the mass density and v the sound velocity close to those obtained for amorphous and “orientational” disordered crystalline materials. Our data would indicate that the TS are intrinsic defects independent of the sample porosity.
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Area Expedition Conference International Conference on High Temperature Superconductors and Materials and Mechanisms of Superconductivity
Notes Export Date: 28 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Regueiro, M.N.; Centro At Approved no
Call Number BT @ luzuriag @ Serial 496
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Author (up) Neerinck, D.; Temst, K.; Baert, M.; Osquiguil, E.; Van Haesendonck, C.; Bruynseraede, Y.; Gilabert, A.; Schuller, I.K.
Title Thermally induced transition in the vortex lattice of Ge/Pb multilayers Type Journal Article
Year 1991 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 185-189 Issue PART 3 Pages 2061-2062
Keywords Germanium And Alloys; Lead And Alloys; Superconducting Films; Thermal Effects; Critical Currents; Multilayers; Metallic Films
Abstract We report on a novel magnetic field dependence of the critical current density of M.B.E. grown Ge/Pb insulator/superconductor multilayers. When the magnetic field is applied perpendicular to the layers, the critical current density Jc drops to a minimum, followed by a broad maximum before finally decaying monotonously to zezero with increasing magnetic field. The dependence of this effect on pinning strength, temperature, and layer thickness suggests either a thermally driven coupling/decoupling transition, or melting of the vortex lattice.
Address Physics Department, University of California, San Diego, CA 92093-0319, United States
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Neerinck, D.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; K.U. Leuven B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 412
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Author (up) Nieva, G.; Lee, B. W.; Guimpel, J.; Iwasaki, H.; Maple, M. B.; Schuller, I.K.
Title Changes in the Pr-induced TC depression of 123 compounds by chemical pressure Type Journal Article
Year 1991 Publication Physica C: Superconductivity Abbreviated Journal Physica C
Volume 185-189 Issue 1 Pages 561-562
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Abstract We present structural data refined from X-ray spectra for R1−xPrxBa2Cu3O7−δ (R=Er, Gd, Eu, Sm, Nd) systems with x=0, 0.1, and 0.4. The evolution of Tc with the ionic radius of the rare earth for different values of x can be related to the Cu2---O4 distance. The effect of chemical pressure on Tc in R1−xPrxBa2Cu3O7−δ systems is opp osite to that of hydrostatic pressure on the Y1−xPrxBa2Cu3O7−δ system.
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Call Number BT @ gnieva @ Serial 439
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Author (up) Pasquini, G.; Levy, P.; Civale, L.; Nieva, G.; Lanza, H.
Title Linear response in the AC susceptibility of vortices in YBa2Cu3O7 crystals with columnar defects Type Journal Article
Year 1997 Publication Physica C: Superconductivity Abbreviated Journal
Volume 274 Issue 1-2 Pages 165-172
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Abstract We explore the AC magnetic susceptibility of YBa2Cu3O7 single crystals with columnar defects. For vortices parallel to the defects the linear response is mainly determined by the Campbell penetration depth with a field independent Labusch parameter indicating that vortices are individually pinned. The small dissipation in this limit is likely to arise from thermal fluctuations of vortex segments between pairs of metastable states (two-level systems) in the Bose glass phase. Tilting vortices away from the tracks results in a reduction of the Bose glass temperature and an increase of the dissipation due to the reduction of the pinning forces. We discuss the onset of nonlinear response as the AC field increases.
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Notes ISI:A1997WG88200021 Approved no
Call Number BT @ hernan @ Serial 243
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Author (up) Puig, J.; Cejas Bolecek, N.R.; Aragón Sánchez, J.; Dolz, M.I.; Konczykowski, M.; Fasano, Y.
Title Bridge in micron-sized Bi2Sr2CaCu2O8 sample act as converging lens for vortices Type Journal Article
Year 2021 Publication Physica C: Superconductivity and its Applications Abbreviated Journal Physica C
Volume 590 Issue Pages 1353948
Keywords Vortex matterMesoscopic samplesStructural properties
Abstract We report on direct imaging of vortex matter nucleated in micron-sized BiSrCaCuO superconducting samples that incidentally present a bridge structure. We find that when nucleating vortices in a field-cooling condition the deck of the bridge acts as a converging lens for vortices. By means of Bitter decoration images allowing us to quantify the enhancement of vortex-vortex interaction energy per unit length in the deck of the bridge, we are able to estimate that the deck is thinner than m. We show that the structural properties of vortex matter nucleated in micron-sized thin samples are not significantly affected by sample-thickness variations of the order of half a micron, an important information for type-II superconductors-based mesoscopic technological devices.
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Call Number BT @ pedrazp @ Serial 878
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