Records |
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 |
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Journal Article |
Year |
1994 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
Volume |
72 |
Issue |
8 |
Pages |
1272 |
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Abstract  |
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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BT @ gnieva @ |
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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 |
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Pages |
4034 |
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Abstract  |
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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BT @ gnieva @ |
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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 |
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Volume |
341 |
Issue |
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Pages |
1285-1286 |
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Abstract  |
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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0921-4534 |
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ISI:000165855700242 |
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BT @ hernan @ |
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221 |
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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 |
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Journal Article |
Year |
1992 |
Publication |
Physical Review B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
46 |
Issue |
21 |
Pages |
14238-14241 |
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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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American Physical Society |
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BT @ pedrazp @ 10.1103/PhysRevB.46.14238 |
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801 |
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Author |
Arce, R.; de la Cruz, F.; Esquinazi, P. |
Title |
Superconducting penetration depth in amorphous metals |
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Journal Article |
Year |
1981 |
Publication |
Solid State Communications |
Abbreviated Journal |
Solid State Commun. |
Volume |
38 |
Issue |
12 |
Pages |
1253-1255 |
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We show that temperature dependent penetration depth measurements can be used to characterize the superconductive behaviour of amorphous metals. |
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0038-1098 |
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BT @ pedrazp @ |
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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 |
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Journal Article |
Year |
2004 |
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Physica C |
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408-410 |
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Pages |
531-532 |
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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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BT @ hernan @ correa04 |
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9 |
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Author |
Monton, C.; Guimpel, J.; de la Cruz, F. |
Title |
Superconducting behaviour of Nb/Co superlattices |
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Journal Article |
Year |
2007 |
Publication |
Applied Surface Science |
Abbreviated Journal |
Appl. Surf. Sci. |
Volume |
254 |
Issue |
1 |
Pages |
375-377 |
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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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0169-4332 |
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ISI:000250800100085 |
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BT @ hernan @ |
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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 |
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Journal Article |
Year |
1979 |
Publication |
Physical Review B |
Abbreviated Journal |
Phys. Rev. B |
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20 |
Issue |
5 |
Pages |
1947-1959 |
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Abstract  |
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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0163-1829 |
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ISI:A1979HP51300019 |
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BT @ hernan @ |
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275 |
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