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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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Decca, R., E. Osquiguil, F. de la Cruz, C. D'Ovidio, M. T. Malachevski, and D. Esparza. "Non linear temperature dependence of the resistivity of LaSrCuO: Effects of Sr content." Solid State Communications 69, no. 4 (1989): 355–357.
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.
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Osquiguil, E., R. Decca, G. Nieva, L. Civale, and F. de la Cruz. "La1.80 Sr0.20 CuO4-delta a clean limit superconductor." Solid State Communications 65, no. 6 (1988): 491–494.
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.
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De La Cruz, F., J. Luzuriaga, E. N. Martinez, and E. J. Osquiguil. "Current-voltage characteristics in collective pinning." Physical Review B 36, no. 13 (1987): 6850–6852.
Abstract: The critical-current curves of amorphous samples which exhibit collective flux pinning have been analyzed, and it was found that the nonlinear part can be fitted by an expression of the form V(I)[(I-IK)/IK]. This form, which could be due to critical behavior, is consistent with an interpretation of the unpinning of vortices in the collective regime as a phase transition between the static flux-line lattice (FLL) and the FLL in steady-state movement as has been proposed by Fisher.
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Esparza, D. A., C. A. D'Ovidio, J. Guimpel, E. Osquiguil, L. Civale, and F. de la Cruz. "The granular nature of bulk superconductivity at 40K in La1.8Sr0.2CuO4." Solid State Communications 63, no. 2 (1987): 137–140.
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.
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Martinez, E. N., V. L. P. Frank, E. J. Osquiguil, and F. de la Cruz. "Dimensional crossovers in collective flux pinning." Solid State Communications 60, no. 2 (1986): 151–155.
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.
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Osquiguil, E., V. L. P. Frank, and F. de la Cruz. "Two dimensional collective flux pinning in melt spun superconducting amorphous Zr70Cu30." Solid State Communications 55, no. 3 (1985): 227–230.
Abstract: We have measured the critical currents in melt spun amorphous Zr70Cu30 and their evolution with heat treatment. We found that the pinning forces may be interpreted in terms of the Larkin-Ovchinnikov two dimensional collective pinning theory.
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Nieva, G., E. N. Martinez, F. de la Cruz, D. A. Esparza, and C. A. D'Ovidio. "Specific heat of La1.8Sr0.2CuO4: Anomaly at the superconducting transition." Physical Review B 36, no. 16 (1987): 8780–8782.
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Osquiguil, E., L. Civale, R. Decca, H. Safar, E. Martinez, G. Nieva, and F. de la Cruz. "The Granular Behavior of LaSrCuO: Oxygen Concentration Effects on the Electrical Resistivity." In High Temperature Superconductors, Mat. Res. Soc. Symposium Proceedings, edited by K. Kitazawa and H. L. Tutler R. C. Dynes ed. M.B. Brosdky, 985. Vol. 99. Pittsburgh, PA: Mater. Res. Soc., 1988.
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López, D., E. Rodríguez, G. Nieva, F. de la Cruz, and S. W. Cheong. "Three-dimensional vortex flux flow in LSCO and YBCO through pseudo dc flux transformer measurements." Physica B: Condensed Matter 194-196, no. 2 (1994): 1977–1978.
Abstract: A pseudo dc flux transformer configuration shows that the flux flow in La2−xSrxCuO4 (x=0.075) and YBa2Cu3O7 single crystals is due to the movement of 3-D vortices across the sample. We show that the loss of c-axis long range vortex correlation is achieved either by thermal fluctuations or by an inhomogeneus Lorentz force acting on the vortices.
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