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de la Cruz, F., D. López, and G. Nieva. "Thermally induced change in the vortex dimensionality of YBa2Cu3O7 single crystals." Philosophical Magazine Part B 70, no. 3 (1994): 773–786.
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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de la Cruz, F., D. López, E. F. Righi, and G. Nieva. "Comparative Study of Vortex Correlation in Twinned and Untwinned YBa2Cu3O7 Single Crystals." In Proceedings of the 10th Anniversary Hts Workshop on Physics, Materials and Applications, edited by B. Batlogg, 395. Singapore: World Scientific Publishing Company, 1996.
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López, D., E. F. Righi, G. Nieva, F. de la Cruz, W. K. Kwok, J. A. Fendrich, G. W. Crabtree, and L. Paulius. "Discontinuous Onset of the c-axis Vortex Correlation at the Melting Transition in YBa2Cu3O7." In Proceedings of the 10th Anniversary Hts Workshop on Physics, Materials and Applications, edited by B. Batlogg, 411. Singapore: World Scientific Publishing Company, 1996.
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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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Arce, R., F. de la Cruz, and H. J. Fink. "Model relating superconductive penetration depth and metallurgical phase separation in amorphous La70Cu30." Solid State Communications 42, no. 8 (1982): 575–577.
Abstract: A model is proposed to account for the large increase in the measured penetration depth of superconducting, amorphous La70Cu30 when the specimens are annealed sufficiently long near, but below, the crystallization temperature. It is suggested that a metallurgical phase separation occurs with domain dimensions in the submicrometer range. Penetration depth measurements as a function of temperature in a weak magnetic field are a useful tool to detect changes in phase separation in high-K materials.
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Luzuriaga, J., C. D'Ovidio, and F. de la Cruz. "Ideal two dimensional flux pinning induced by annealing in superconducting amorphous Zr75Rh25." Solid State Communications 57, no. 9 (1986): 753–756.
Abstract: By annealing amorphous Zr75Rh25 prepared by melt spinning an ideal behaviour of the critical current was observed, in which the measured pinning forces are seen to follow the two dimensional Larkin-Orchivnikov theory. In the region where this theory is valid the changes in the pinning forces can be explained by the changes in the superconducting matrix and it can be assumed that the pinning centers do not change with the heat treatment.
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Arce, R., L. Civale, J. Luzuriaga, J. Guimpel, and F. de la Cruz. "Surface normal regions in superconducting Zr70Cu30 induced by thermal relaxation." Solid State Communications 48, no. 12 (1983): 1027–1030.
Abstract: Penetration depth measurements show that thermal heat treatment in amorphous Zr70Cu30 induces a normal region 5000 Å thick at the surface of ultrarapid quenched ribbons. Upper critical field measurements indicate that the new induced phase is a normal one while the rest of the sample remains as a homogeneous superconducting phase.
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Civale, L., F. de la Cruz, and J. Luzuriaga. "Critical temperature and density of states in amorphous Zr70Cu30." Solid State Communications 48, no. 4 (1983): 389–391.
Abstract: By means of thermal heat treatment of amorphous Zr70Cu30 it is shown that the induced decrease in critical temperature is followed by a reduction in the electronic density of states of the same magnitude as that obtained by changing the Cu concentration. This result indicates that the density of states is the fundamental microscopic parameter determining the superconducting behavior.
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Arce, R., F. de la Cruz, and P. Esquinazi. "Superconducting penetration depth in amorphous metals." Solid State Communications 38, no. 12 (1981): 1253–1255.
Abstract: We show that temperature dependent penetration depth measurements can be used to characterize the superconductive behaviour of amorphous metals.
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Luzuriaga, J., and F. de la Cruz. "Reversible magnetization of surface superconductivity." Solid State Communications 25, no. 8 (1978): 605–607.
Abstract: Direct measurements of the surface superconducting magnetization of the PbTl system shows that this state is a thermodynamic reversible one.
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