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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 (down) 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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Call Number BT @ gnieva @ Serial 443
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Author de la Cruz, F.; López, D.; Nieva, G.
Title Thermally induced change in the vortex dimensionality of YBa2Cu3O7 single crystals Type Journal Article
Year 1994 Publication Philosophical Magazine Part B Abbreviated Journal Philos. Mag. B
Volume (down) 70 Issue 3 Pages 773 - 786
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Abstract Transport measurements in YBa2Cu3O7 single crystals using a modification of the d.c. flux transformer configuration are reported. We show that, for applied magnetic fields in the crystallographic c direction, the vortex correlation length in this direction is reduced to values smaller than the thickness of the sample. The reduction can be induced either by thermal disorder (linear response) or by flux cutting after the vortices reach a critical velocity (nonlinear response). The results show that, in the transition from a vortex-glass state to a vortex-liquid state, the vortices are effectively three dimensional in character. A two-dimensional regime is induced at higher temperatures well inside the reversibility region.
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Call Number BT @ gnieva @ Serial 456
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Author Valenzuela, S.O.; Ferrari, H.; Bekeris, V.; Marconi, M.C.; Guimpel, J.; de la Cruz, F.
Title Nonconventional short-time dc magnetometer for superconducting films Type Journal Article
Year 1998 Publication REVIEW OF SCIENTIFIC INSTRUMENTS Abbreviated Journal
Volume (down) 69 Issue 1 Pages 251-254
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Abstract A nonconventional technique for the measurement of magnetic relaxation in superconducting films at short times (similar to 10(-5) s) is described. This technique combines the application of a pulsed magnetic field and a synchronized high-energy pulsed laser. Remanent magnetic relaxation in (Y;Gd)Ba2Cu3O7-delta thin films is reported over five decades time at reduced temperatures above 0.8. (C) 1998 American Institute of Physics.
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ISSN 0034-6748 ISBN Medium
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Notes ISI:000071578800041 Approved no
Call Number BT @ hernan @ Serial 185
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Author Decca, R.; Osquiguil, E.; de la Cruz, F.; D'Ovidio, C.; Malachevski, M.T.; Esparza, D.
Title Non linear temperature dependence of the resistivity of LaSrCuO: Effects of Sr content Type Journal Article
Year 1989 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume (down) 69 Issue 4 Pages 355-357
Keywords Ceramic Materials; Lanthanum Compounds--Electric Conductivity; Superconductivity; Ceramic Superconductors; Superconducting Materials
Abstract The linear temperature dependence of the electrical resistivity has been taken to be one of the characteristic features of the ceramic superconductors. Measurements of the electrical resistance of the LaSrCuO system in a wide temperature range show that the previous statement is only an approximation valid for some values of the Sr concentration.
Address Applied Research Department, Centro At'omico Bariloche
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ISSN 00381098 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 2; Export Date: 17 April 2009; Source: Scopus; CODEN: SSCOA; Language of Original Document: English; Correspondence Address: Decca, R.; Basic Research Department; Centro At Approved no
Call Number BT @ osquigui @ Serial 414
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Author Osquiguil, E.; Decca, R.; Nieva, G.; Civale, L.; de la Cruz, F.
Title La1.80 Sr0.20 CuO4-delta a clean limit superconductor Type Journal Article
Year 1988 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume (down) 65 Issue 6 Pages 491-494
Keywords CERAMIC MATERIALS; LANTHANUM COMPOUNDS – Electric Conductivity; CERAMIC SUPERCONDUCTORS; CLEAN LIMIT SUPERCONDUCTOR; HIGH-TEMPERATURE SUPERCONDUCTORS; OXYGEN CONCENTRATION; SUPERCONDUCTING MATERIALS
Abstract The electrical resistivity of the superconductor La1.80Sr0.20Cu04-? has been measured in a wide range of temperatures as a function of oxygen and vacuum heat treatments. The resistivity changes reversibly orders of magnitude with oxygen concentration. There is no sign of saturation at high temperatures, even for samples where the resistivity is increased by heat treatment in vacuum. Using the experimental data and general arguments it is concluded that the ceramic superconductors are high ? materials in the clean limit.
Address Instituto Balseiro 8400 Bariloche, R.N., Argentina# # Comisi
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: SSCOA; Language of Original Document: English; Correspondence Address: Osquiguil, E. Approved no
Call Number BT @ osquigui @ Serial 416
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Author Guimpel, J.; de la Cruz, M.E.; de la Cruz, F.; Fink, H.J.; Laborde, O.; Villegier, J.C.
Title Size dependence of the Superconducting critical temperature and fields of Nb/Al multilayers Type Journal Article
Year 1986 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume (down) 63 Issue 1-2 Pages 151-165
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Abstract The critical temperatureT cof Nb/Al multilayers decreases as the total sample thicknessd Tis decreased while the thickness of each Nb and Al layer is kept constant. To understand this behavior, models based on the proximity effect and on weak two-dimensional (2D) localization are employed. The latter uses a characteristic length, the thermal diffusion length, in relation tod Tto obtain 2D behavior and leads to a reasonable explanation ofT c(d T). It is also found that the slope atT c(d T) of the critical magnetic field perpendicular to the layers is independent ofd Twhen the Nb and Al layer thicknesses are kept constant. The angular dependence of the critical field is also measured.
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ISSN 0022-2291 ISBN Medium
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Notes ISI:A1986C112200008 Approved no
Call Number BT @ hernan @ Serial 193
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Author Correa, V.F.; Herbsommer, J.A.; Kaul, E.E.; de la Cruz, F.; Nieva, G.
Title Order-disorder transition and the zero-dimensional vortex pinning regime in Bi2Sr2CaCu2O8+delta Type Journal Article
Year 2001 Publication PHYSICAL REVIEW B Abbreviated Journal
Volume (down) 63 Issue 9 Pages 092502
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Abstract We make a comparative study between the ab plane's dc critical current and the ac transverse magnetic permeability μ(perpendicular to) in the Campbell limit for optimally doped and overdoped Bi2Sr2CaCu2O8+delta samples. We focus attention on the low-temperature region [T/T-c(0) < 0.25], where the transition to the zero-dimensional Larkin limit is detected by the critical current as well as by a rapid change of the Labusch parameter with temperature. The order-disorder transition, characterized by the second peak in magnetization, disappears in the presence of this zero-dimensional pinning regime.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:000167312000016 Approved no
Call Number BT @ hernan @ Serial 218
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Author Esparza, D.A.; D'Ovidio, C.A.; Guimpel, J.; Osquiguil, E.; Civale, L.; de la Cruz, F.
Title The granular nature of bulk superconductivity at 40K in La1.8Sr0.2CuO4 Type Journal Article
Year 1987 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume (down) 63 Issue 2 Pages 137-140
Keywords CERAMIC MATERIALS; GRANULAR MATERIALS; LANTHANUM COMPOUNDS – Electric Conductivity; CRITICAL FIELDS; HIGH TEMPERATURE SUPERCONDUCTOR; MAGNETIC FLUX EXPULSION; TEMPERATURE DEPENDENCE; SUPERCONDUCTING MATERIALS
Abstract We have measured the electrical resistivity, magnetic flux expulsion and critical fields of the new high temperature superconductor La1.8Sr0.2CuO4 after different heat treatments. Our data show that the complete flux expulsion in these samples is consistent with the presence of shielding currents induced in multiple connected structures. The magnetization measurements indicate that the lowest field where flux penetrates into the sample should not be taken to be the bulk Hcl. It is shown that the absolute value of the electrical resistivity and its temperature dependence are not correlated with the superconducting critical field and temperature. We discuss the behaviour of the superconducting parameters and their relation with the electrical resistivity.
Address Basic Research Department, Centro At
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ISSN 00381098 (ISSN) ISBN Medium
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: SSCOA; Language of Original Document: English; Correspondence Address: Esparza, D.A.; Applied Research Department; Centro At Approved no
Call Number BT @ osquigui @ Serial 418
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Author Fasano, Y.; Menghini, M.; de la Cruz, F.; Nieva, G.
Title Weak interaction and matching conditions for replicas of vortex lattices Type Journal Article
Year 2000 Publication PHYSICAL REVIEW B Abbreviated Journal
Volume (down) 62 Issue 22 Pages 15183-15189
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Abstract We present experiments demonstrating the conditions under which weak interaction between replicas of vortex structures break their translational and rotational symmetry. The Fe clumps introduced by Bitter decorations of vortex structures are used to induce an extremely weak interaction fur subsequent vortex structures in low and high temperature superconducting crystals. The matching between the Fe pattern acid the vortex configuration require the structure to be prepared under quite stringent conditions: The field creating the structure has to be the same in magnitude although it can differ in orientation from that used for the preparation of the Fe pattern. The interaction between vortex replicas as represented by the Fe clumps of Bitter decorations makes it possible to differentiate the vortex nucleation and propagation mechanisms in low and high temperature superconductors.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:000165883800075 Approved no
Call Number BT @ hernan @ Serial 219
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Author Martinez, E.N.; Frank, V.L.P.; Osquiguil, E.J.; de la Cruz, F.
Title Dimensional crossovers in collective flux pinning Type Journal Article
Year 1986 Publication Solid State Communications Abbreviated Journal Solid State Commun
Volume (down) 60 Issue 2 Pages 151-155
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Abstract The pinning force density in ribbons of melt spun (a) Zr70Cu30 is found to obey the Larkin-Ovchinnikov theory of collective pinning by dislocation loops, and shows two and three dimensional behaviour, besides an intermediate regime not contemplated by the theory. The dimensional crossovers allow determination of the radius of action of the pinning forces which is shown to be proportional to the coherence length. Its magnitude is too small, which points to quantitative shortcomings of the current theory.
Address Centro At
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ISSN 00381098 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 1; Export Date: 17 April 2009; Source: Scopus; CODEN: SSCOA; Language of Original Document: English; Correspondence Address: Martinez, E.N. Approved no
Call Number BT @ osquigui @ Serial 419
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