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Bressan, O. J., A. E. Ridner, and F. de la Cruz. "Low angle electron scattering in thermal resistivity." Journal of Physics F: Metal Physics 5 (1975): 1902–1909.
Abstract: Electrical ( rho ) and thermal (W) resistivity measurements in very dilute In alloys between 1K and 4K show a temperature dependence expressed by rho = rho 0+ beta T5 and WT=(WT)0+AT3+BT5. The BT5 term in the thermal resistivity is due to a contribution from a 'diffusion-like process' of electrons over the Fermi surface, as is the one that describes the temperature dependence of the electrical resistivity. This claim is supported by the experimental fact that the Lorenz number defined as L= beta /B coincides with the value given by L= rho 0/(WT)0 which in turn agrees with the free electron value within 15%.
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Ridner, A., E. N. Martínez, and F. de la Cruz. "Surface-Temperature Determination in the Kapitza Problem." Physical Review Letters 35, no. 13 (1975): 855–858.
Abstract: It is shown that surface superconductivity can be used as a localized thermometer. Its application to the study of the thermal boundary resistance at a Pb-4He interface provides the first experimental evidence for the existence of a rapid temperature variation within microscopic distances from the surface.
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Arce, R., F. de la Cruz, and P. Esquinazi. "Superconducting penetration depth in amorphous La70Cu30." Physica B+C 108B (1981): 1253–1254.
Abstract: It is shown that weak field penetration depth measurements can be used to determine the change in the normal and superconducting behaviour of amorphous samples, when heat-treated below the crystallization temperature. The results are used to discuss the validity of BCS-Gorkov relations, when applied to these materials.
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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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Civale, L., and F. de la Cruz. "Anomalous behavior of superconducting samples with a fixed number of vortices." Physical Review B 36, no. 7 (1987): 3560–3564.
Abstract: We report an anomalous reversible temperature dependence of the magnetization of amorphous type-II superconductors. The experimental results were obtained studying the vortex pinning in samples with very low vortex concentration. The anomaly is shown to be a consequence of the lack of flux quantization in finite samples.
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López, D., R. Decca, and F. de la Cruz. "Topological pinning and flux flow in ceramic superconductors." Solid State Communications 79, no. 11 (1991): 959–962.
Abstract: The transport current dissipation in the high Tc superconducting ceramic La1.85Sr0.15CuO4−δ shows a sin2 Θ voltage dependence where Θ is the angle between the transport current and the magnetic field. This result and the experimental evidence of an angle independent critical current cannot be explained by the conventional description of flux motion in homogeneous type II superconductors. The results are analyzed in the framework of a granular system where pinning is induced by the topological distribution of current flowing through a multiply connected medium. The dissipation in the superconducting state is found to be due to two additive contributions, one induced by the movement of magnetic flux and the other associated to dissipation in the Josephson junction.
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Guimpel, J., C. Monton, N. Haberkorn, and F. de la Cruz. "Magnetic behaviour of superconductor/ferromagnet metallic and perovskite based superlattices." physica status solidi (c) 4, no. 11 (2007): 4174–4180.
Abstract: We present a study of the magnetic behaviour of superconducting/ferromagnetic superlattices, both for metallic and perovskite based systems. In the first case we find that the response is determined by the ferromagnetic layer regime. If these layers are very thin, no ferromagnetism is observed, but the superconducting layers are decoupled, and the superlattice behaves as a stack of independent superconducting films. For thicker ferromagnetic films, ferromagnetism is established and the effective field resulting from the superposition of stray and applied fields dominates the superconducting response of the superlattice. For the perovskite based superlattices, the physical properties are more affected by interface disorder. In this case we have found that the behaviour can be interpeted as charge carrier transfer between both materials, inducing a change in the magnetic character of the manganite. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Safar, H., C. Durán, J. Guimpel, L. Civale, J. Luzuriaga, E. Rodríguez, F. de la Cruz, C. Fainstein, L. F. Schneemeyer, and J. V. Waszczak. "Logarithmic to nonlogarithmic flux creep transition and magnetic flux hardening in BiSrCaCuO superconducting ceramics." Physica C: Superconductivity 162-164, Part 1 (1989): 665–666.
Abstract: A sharp temperature and field dependent transition from a logarithmic to a non-logarithmic flux creep behavior has been found in BiSrCaCuO superconductors. The transition is not followed by any noticeable change in the magnetization. However, vibrating reed measurements show that it coincides with a strong hardening of the magnetic structure. The transition occurs at fields and temperatures well below the reversibility line. The possible relation to the recently proposed flux lattice melting is discussed.
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Safar, H., C. Durán, J. Guimpel, L. Civale, J. Luzuriaga, E. Rodriguez, F. de la Cruz, C. Fainstein, L. F. Schneemeyer, and J. V. Waszczak. "Logarithmic-to-nonlogarithmic flux-creep transition and magnetic-flux hardening in Bi-Sr-Ca-Cu-O superconducting ceramics." Physical Review B 40, no. 10 (1989): 7380.
Abstract: A sharp temperature- and field-dependent transition from a logarithmic to a nonlogarithmic flux-creep behavior has been found in Bi-Sr-Ca-Cu-O superconductors. The transition is not followed by any noticeable change in the magnetization. However, vibrating-reed measurements show that it coincides with a strong hardening of the magnetic structure. The transition occurs at fields and temperatures well below the reversibility line. The possible relation to the recently proposed flux lattice melting is discussed.
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Safar, H., E. Rodriguez, F. de la Cruz, P. L. Gammel, L. F. Schneemeyer, and D. J. Bishop. "Observation of two-dimensional vortices in Bi2Sr2CaCu2Ox." Physical Review B 46, no. 21 (1992): 14238–14241.
Abstract: We report transport measurements in the mixed state of single crystals of Bi2Sr2CaCu2Ox using a modified version of the dc flux transformer geometry pioneered by Giaever in low-Tc materials. We find that over a wide range of the phase diagram the vortices are effectively two dimensional in character. Our results suggest that vortex cutting is an efficient process and that it is unlikely that the vortices are strongly entangled in this region of the phase diagram.
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