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López, D., E. A. Jagla, E. F. Righi, E. Osquiguil, G. Nieva, E. Morré, F. de la Cruz, and C. A. Balseiro. "Dynamic softening of vortex lines in YBa2Cu3O7−δ single crystals." Physica C: Superconductivity 260, no. 3-4 (1996): 211–216.
Abstract: Transport measurements in the mixed state of oxygen-deficient YBa2Cu3O7−δ single crystals using the flux transformer configuration show that the flux liquid changes with increasing anisotropy from strongly correlated to uncorrelated in the field direction. For intermediate coupling, the current inducing loss of vortex correlation has a maximum near the irreversibility temperature. Thus, an effective softening of vortex lines with decreasing temperature is detected. We propose a simple model that accounts for this behavior by including the effects of the pinning potential on the dynamics of vortices.
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Morré, E., S. Grigera, E. Osquiguil, G. Nieva, and F. de la Cruz. "Angular restrictions on the glass transition and on the c-axis correlated liquid phase in twinned YBa2Cu3O7-?" Physics Letters A 233, no. 1-2 (1997): 130–134.
Abstract: We have measured the angular dependence of the vortex velocity correlation temperature Tth(H) in twinned YBa2Cu3O7-? single crystals. The data show that the c-axis correlated vortex liquid phase exists up to angles much larger than expected within a single vortex pinning picture. Despite this, the second-order solid-liquid glass transition is shown to be restricted only to external magnetic fields applied within a few degrees from the c-axis direction.
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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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