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Author Safar, H.; Gammel, P.L.; Huse, D.A.; Majumdar, S.N.; Schneemeyer, L.F.; Bishop, D.J.; Lopez, D.; Nieva, G.L.; de la Cruz, F.
Title Observation of a nonlocal conductivity in the mixed state of YBa2Cu3O7-d: Experimental evidence for a vortex line liquid Type Journal Article
Year 1994 Publication Physical Review Letters Abbreviated Journal Phys. Rev. Lett.
Volume 72 Issue 8 Pages 1272
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Abstract (up) We report on transport measurements in the mixed state of YBa2Cu3O7 single crystals using the dc flux transformer geometry. In the vortex fluid regime we have observed the onset of a nonlocal conductivity. At lower temperatures, close to but above the phase transition temperature the vortices become effectively three dimensional in character. This is in sharp contrast to recent flux transformer experiments on Bi2Sr2CaCu2O which have failed to see a nonlocal conductivity, confirming the two-dimensional character at high temperatures of the vortices in that system. These observations suggest that in a finite temperature interval, the vortex state in YBa2Cu3O7 is a line liquid.
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Call Number BT @ gnieva @ Serial 443
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Author López, D.; Righi, E. F.; Nieva, G.; de la Cruz, F.
Title Coincidence of Vortex-Lattice Melting and Loss of Vortex Correlation along the c Direction in Untwinned YBa2Cu3O7-δ Single Crystals Type Journal Article
Year 1996 Publication Physical Review Letters Abbreviated Journal Phys. Rev. Lett.
Volume 76 Issue Pages 4034
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Abstract (up) We report on transport measurements using the dc flux transformer configuration in clean and twinned single crystals of YBa2Cu3O7-δ. We show that correlated disorder changes not only the order of the solid-liquid phase transition but also the nature of the vortices in the liquid state. In clean crystals, melting is shown to take place between a solid of vortex lines and a liquid with no correlation in the direction of the magnetic field.
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Call Number BT @ gnieva @ Serial 448
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Author Correa, V.F.; Herbsommer, J.A.; Kaul, E.E.; de la Cruz, F.; Nieva, G.
Title Onset of the 0-dimensional vortex pinning behavior in the optimally doped and overdoped Bi2Sr2CaCu2O8+delta system Type Journal Article
Year 2000 Publication PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Abbreviated Journal
Volume 341 Issue Pages 1285-1286
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Abstract (up) We report results of transverse AC magnetic permeability in the linear regime and DC magnetization loops for optimally doped and oxygen overdoped samples of Bi2Sr2CaCu2O8+delta The data cover the low temperature (T < 25K) and low held (H-a < 1000 Oe) region of the magnetic (H-a-T) phase diagram. In optimally doped as well as in overdoped samples a crossover to a O-dimensional pinning regime (Larkin length, L-C(C), shorter than the inter-plane CuO2 distance) is observed at a characteristic temperature Too for all investigated fields. The order-disorder transition, identified by the second peak in magnetization and a non monotonous field dependence of the AC penetration depth, is quenched below T-0D.
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ISSN 0921-4534 ISBN Medium
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Notes ISI:000165855700242 Approved no
Call Number BT @ hernan @ Serial 221
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Author Safar, H.; Rodriguez, E.; de la Cruz, F.; Gammel, P.L.; Schneemeyer, L.F.; Bishop, D.J.
Title Observation of two-dimensional vortices in Bi2Sr2CaCu2Ox Type Journal Article
Year 1992 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 46 Issue 21 Pages 14238-14241
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Abstract (up) We report transport measurements in the mixed state of single crystals of Bi2Sr2CaCu2Ox using a modified version of the dc flux transformer geometry pioneered by Giaever in low-Tc materials. We find that over a wide range of the phase diagram the vortices are effectively two dimensional in character. Our results suggest that vortex cutting is an efficient process and that it is unlikely that the vortices are strongly entangled in this region of the phase diagram.
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Publisher American Physical Society Place of Publication Editor
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Call Number BT @ pedrazp @ 10.1103/PhysRevB.46.14238 Serial 801
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Author Arce, R.; de la Cruz, F.; Esquinazi, P.
Title Superconducting penetration depth in amorphous metals Type Journal Article
Year 1981 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 38 Issue 12 Pages 1253-1255
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Abstract (up) We show that temperature dependent penetration depth measurements can be used to characterize the superconductive behaviour of amorphous metals.
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ISSN 0038-1098 ISBN Medium
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Call Number BT @ pedrazp @ Serial 557
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Author Correa, V.F.; Nieva, G.; Pastoriza, H.; de la Cruz, F.
Title The true pinning force range in Bi2Sr2CaCu2O8 single crystals at low temperatures Type Journal Article
Year 2004 Publication Physica C Abbreviated Journal
Volume 408-410 Issue Pages 531-532
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Abstract (up) We study the effective profile of the pinning potential well in Bi$2$Sr$2$CaCu$_2$O8+δ single crystals using transverse ac magnetic susceptibility. The results show that the harmonic approximation for the potential well (linear regime) is valid up to vortex displacements $r\simeqξ$, where ξ, is the coherence length. In spite of this, it is necessary to induce displacements of the vortex structure much larger than ξ to depin it from its potential. This is shown to take place even in the single vortex limit.
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Call Number BT @ hernan @ correa04 Serial 9
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Author Monton, C.; Guimpel, J.; de la Cruz, F.
Title Superconducting behaviour of Nb/Co superlattices Type Journal Article
Year 2007 Publication Applied Surface Science Abbreviated Journal Appl. Surf. Sci.
Volume 254 Issue 1 Pages 375-377
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Abstract (up) We study the superconducting and magnetic behaviour of Nb/Co superlattices, for superconducting Nb layer thickness of 44 nm and Co layer thickness less than 1 nm. In this limit no ferromagnetism is observed for Co. The superlattice behaves as independent superconducting Nb layers. We obtain the penetration depth and superconducting gap of the material, and analyze the results in terms of microscopic models and theories. (C) 2007 Elsevier B.V. All rights reserved.
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ISSN 0169-4332 ISBN Medium
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Notes ISI:000250800100085 Approved no
Call Number BT @ hernan @ Serial 149
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Author de la Cruz, F.; Fink, H.J.; Luzuriaga, J.
Title Temperature dependence of the superconducting giant-vortex state. Theory and Experiment Type Journal Article
Year 1979 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 20 Issue 5 Pages 1947-1959
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Abstract (up) When a type-I superconductor with a surface nucleation field Hc3(T)>Hc(T) (thermodynamic critical field) is thermally cycled in an axially applied magnetic field H0 between the temperatures T(Hc3) and about T(Hc), experiments show that the magnetization changes reversibly. The latter is diamagnetic near T(Hc3) but can be paramagnetic just above T(Hc). This behavior is explained by assuming that the fluxoid quantum number b is fixed at the transition from the normal to the superconducting state and retained at lower temperatures. The value of b is determined almost entirely by the flux at the transition which is enclosed by a contour located at a distance ξ1.7 from the surface inside the cylinder (ξ is the coherence length). The temperature variation of the order parameter f at the surface of the cylinder, the magnetization m, and the temperature at which m=0 for f≠0 are calculated for R>>ξ. Conservation of the fluxoid quantum number, while T is varied causes the two opposing surface currents to become imbalanced. This is the source of the observed para- and diamagnetism.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:A1979HP51300019 Approved no
Call Number BT @ hernan @ Serial 275
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