Fasano, Y., M. de Seta, M. Menghini, H. Pastoriza, and F. de la Cruz. "Imaging the structure of the interface between symmetries interconnected by a discontinuous transition." Solid State Communications 128, no. 3-4 (2003): 51–55.
Abstract: We have been able to observe with single particle resolution the interface between two structural symmetries that cannot be interconnected by a continuous transition. By means of an engineered 2D potential that pins the extremity of vortex strings a square symmetry was imposed at the surface of a 3D vortex solid. Using the Bitter decoration technique and on account of the continuous vortex symmetry, we visualize how the induced structure transforms along the vortex direction before changing into the expected hexagonal structure at a finite distance from the surface.
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Esquinazi, P., M. E. de la Cruz, A. Ridner, and F. de la Cruz. "Heat treatment effects in amorphous metals: Zr70Cu30 and La70Cu30." Solid State Communications 44, no. 6 (1982): 941–944.
Abstract: We measured the electrical resistivity (4–300 K), superconducting critical temperature and thermal conductivity (0.5–7 K) of the amorphous metals Zr70Cu30 and La70Cu30. Heat treatments below crystallization temperature induced changes in these properties. In particular, in the first stage of the annealing of Zr70Cu30 there are systematic changes in the thermal conductivity and the critical temperature, while the electrical resistivity remains constant. We show that there is no simple correlation between the thermal conductivity processes in the low temperature and plateau regions. We also show that the thermal conductivity of as quenched La70Cu30 is typical of amorphous metals, contrary to information previously reported.
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Esquinazi, P., M. E. de la Cruz, and F. de la Cruz. "Heat treatment effects in La70Cu30 amorphous system." Physica B+C 108B, no. 1-3 (1981): 1215–1216.
Abstract: It is shown that superconductivity is a useful tool to investigate the evolution of the amorphous state, when heat treatment below the crystallization temperature.
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Esquinazi, P., and F. de la Cruz. "Phonon thermal conductivity limited by electron scattering in amorphous Zr70Cu30." Physical Review B 27, no. 5 (1983): 3069–3072.
Abstract: The low-temperature thermal conductivity of amorphous Zr70Cu30 is investigated. The lattice thermal conductivity as limited by electrons in the superconducting state has been obtained at temperatures close to Tc. This has allowed for the first time the verification of the temperature dependence of the phonon conductivity as predicted by Bardeen, Rickayzen, and Tewordt. The analysis of the data in the normal and superconducting state shows that Matthiessen's rule can be used in amorphous metals to separate the different scattering processes.
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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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Duran, C., J. Yazyi, F. de la Cruz, D. J. Bishop, D. B. Mitzi, and A. Kapitulnik. "Flux-lattice melting, anisotropy, and the role of interlayer coupling in Bi-Sr-Ca-Cu-O single crystals." Physical Review B 44, no. 14 (1991): 7737–7740.
Abstract: We have used the high-Q mechanical-oscillator technique to probe the vortex-lattice structure in high-quality Bi-Sr-Ca-Cu-O single crystals over a wide range of magnetic fields (200 Oe to 40 kOe), and relative orientations θ between the magnetic field and the crystalline c^ axis. In addition to the large softening and dissipation peak previously observed and interpreted as due to flux-lattice melting, another distinctly different peak at higher temperatures is seen. The temperatures where the dissipation peaks take place are solely defined by the parallel component of the field cosθ, while the restoring force on the oscillator is due to both field components. We suggest that the two peaks are due to the softening of interplanar coupling at the low-temperature peak, and melting or depinning of the two-dimensional pancake vortices at the higher-temperature peak.
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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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de la Cruz, M. E., E. J. P. Godfrin, F. de la Cruz, and C. de Allende. "Superconducting intermediate state in cadmium." Solid State Communications 18, no. 6 (1976): 747–749.
Abstract: Perpendicular magnetic critical fields for cadmium foils were measured to thicknesses below the temperature dependent coherence length. The presence of supercooling indicates first-order thermodynamic transitions for all samples. A modification of Davies' model leads to a good fit of the experimental data.
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de la Cruz, F., H. Pastoriza, D. López, M. F. Goffman, A. Arribére, and G. Nieva. "Consequences of 3D-2D vortex decoupling on the phase diagram of HTS." Physica C: Superconductivity 235-240, no. 1 (1994): 83–86.
Abstract: We discuss the quench of the long range order in the direction parallel and perpendicular to the field, in the mixed state of BSCCO(2212) and YBCO(123) single crystals. The experimental data show that the high temperature vortex phase in both systems is an uncorrelated liquid phase in all directions.
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de la Cruz, F., M. D. Maloney, and M. Cardona. "Variation of the Ratio Hc3/Hc2 in the Immediate Vicinity of ${T}_{c}$." Physical Review 187, no. 2 (1969): 766–767.
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