Grigera, S. A., E. Morré, E. Osquiguil, G. Nieva, and F. De la Cruz. "Nonlocal transport properties and size effects in heavily twinned YBa2Cu3O7-delta single crystals." Solid State Communications 107, no. 7 (1998): 335–339.
Abstract: We demonstrate experimentally that when the vortex correlation length in the liquid state becomes of the order of the sample thickness, size effects dominate the transport properties of the macroscopic vortex structures, implying a nonlocal response in the transformer experiments.
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Righi, E. F., S. A. Grigera, G. Nieva, and F. de la Cruz. "Vortex phase coherence along the c axis in YBa2Cu3O7-d." Superconduvtivity Reviews 2 (1998): 205.
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Grigera, S. A., E. Morre, E. Osquiguil, G. Nieva, and F. de la Cruz. "Two-step liquid-solid vortex transition with the field along the ab planes in YBa2Cu3O7-delta crystals." PHYSICAL REVIEW B 59, no. 17 (1999): 11201–11204.
Abstract: Resistivity measurements for different Lorentz force configurations and the detection of the longitudinal vortex velocity correlation length, with the magnetic field applied parallel to the ab planes, in the mixed state of clean and twinned YBa2Cu3O7-delta single crystals,' support the existence of a vortex-smectic phase when the vortices interact with an attractive periodic potential. The transition from the vortex-liquid to the vortex-solid state is shown to be achieved in two steps, a continuous transition from a liquid to a possible smectic phase and another continuous one from the smectic phase to a solid. [S0163-1829(99)09413-8].
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Fasano, Y., M. Menghini, F. de la Cruz, and G. Nieva. "Weak interaction and matching conditions for replicas of vortex lattices." PHYSICAL REVIEW B 62, no. 22 (2000): 15183–15189.
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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Correa, V. F., J. A. Herbsommer, E. E. Kaul, F. de la Cruz, and G. Nieva. "Onset of the 0-dimensional vortex pinning behavior in the optimally doped and overdoped Bi2Sr2CaCu2O8+delta system." PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 341 (2000): 1285–1286.
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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Correa, V. F., G. Nieva, and F. de la Cruz. "Vortex softening: Origin of the second peak effect in Bi2Sr2CaCu2O8+delta." PHYSICAL REVIEW LETTERS 87, no. 5 (2001): 057003.
Abstract: Magnetic hysteresis and transverse ac permeability measurements in Bi2Sr2CaCu2O8+delta allow a comparative analysis of the critical current with the elastic response of vortex structures, in equilibrium with their pinning potential, in the field and temperature region where the second peak is detected. This study provides strong evidence that the second peak has its origin in changes of the elastic equilibrium properties of the vortex structures.
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Correa, V. F., J. A. Herbsommer, E. E. Kaul, F. de la Cruz, and G. Nieva. "Order-disorder transition and the zero-dimensional vortex pinning regime in Bi2Sr2CaCu2O8+delta." PHYSICAL REVIEW B 63, no. 9 (2001): 092502.
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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Grigera, S. A., T. S. Grigera, E. F. Righi, G. Nieva, and F. de la Cruz. "Flux-cutting in YBa2Cu3O7-delta revisited." PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 371, no. 3 (2002): 237–242.
Abstract: In this paper we present an analysis of the response of the vortices in YBa2Cu3O7-delta to different configurations of applied driving forces. The use of inhomogeneous current allows us to induce vortex cutting. We determine the maximum current injected in different electrical contact distributions which preserves vortex integrity, and we show that vortex cutting cannot be explained by a single vortex picture. (C) 2001 Elsevier Science B.V. All rights reserved.
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Maiorov, B., A. V. Silhanek, F. De la Cruz, and E. Osquiguil. "Comment on “strong vortex liquid correlation from multiterminal measurements on untwinned YBa2Cu3O7-? single crystals”." Physical Review Letters 88, no. 13 (2002): 1397031.
Abstract: Multiterminal measurements using experimental technique on twinned and untwinned YBa2Cu3O7-? crystals were presented. Inhomogeneous current distribution acting upon an uncorrelated vortex system showed that the dissipation of voltage at the top was larger than at the bottom. The behavior of the current voltage curves showed that the result Vtop = Vbot was a consequence of the limited voltage sensitivity.
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Maiorov, B., A. V. Silhanek, F. De la Cruz, E. Osquiguil, A. Rydh, and Rapp. "Comment on “strong vortex liquid correlation from multiterminal measurements on untwinned YBa2Cu3O7-? single crystals” [2] (multiple letters)." Physical Review Letters 88, no. 13 (2002).
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