Correa, V. F., G. Nieva, H. Pastoriza, and F. de la Cruz. "The true pinning force range in Bi2Sr2CaCu2O8 single crystals at low temperatures." Physica C 408-410 (2004): 531–532.
Abstract: We study the effective profile of the pinning potential well in Bi$2$Sr$2$CaCu$_2$O8+δ single crystals using transverse ac magnetic susceptibility. The results show that the harmonic approximation for the potential well (linear regime) is valid up to vortex displacements $r\simeqξ$, where ξ, is the coherence length. In spite of this, it is necessary to induce displacements of the vortex structure much larger than ξ to depin it from its potential. This is shown to take place even in the single vortex limit.
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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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Ridner, A., F. de la Cruz, and E. N. Martinez. "Surface superconductivity and Kapitza resistance." In Phonon Scattering in Condensed Matter, edited by H. J. Maris, 199–202. New York: Plenum Publishing Corp., 1980.
Abstract: It has been shown1 that surface superconductivity can be used as a localized thermomether to study the temperature close to an interface through which heat is being transported. Knowledge of the temperature profile in the interface region provides evidence which any theory of the heat transport mechanism must take into account. For interfaces between pure lead and HeII we have previously found1 clear differences between extrapolated surface temperatures Tk. and Tm, measured within some 1000Ã… of the interface using a superconducting thermometer. (The reader is refered to ref.1 for details on the experimental method).
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Monton, C., F. de la Cruz, and J. Guimpel. "Magnetic state modification induced by superconducting response in ferromagnet/superconductor Nb/Co superlattices." PHYSICAL REVIEW B 77, no. 10 (2008).
Abstract: Magnetization measurements in superconductor/ferromagnet Nb/Co superlattices show a complex behavior as a function of temperature, applied field, and sample history. Based on a simple model, it is shown that this behavior is due to an interplay between the superconductor magnetization temperature dependence, the ferromagnet magnetization time dependence, and the stray fields of both materials. It is also shown that the magnetic state of the Co layers is modified by the Nb superconducting response, implying that the problem of a superconductor/ferromagnetic heterogeneous sample has to be solved in a self-consistent manner.
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Monton, C., J. Guimpel, and F. de la Cruz. "Superconducting behaviour of Nb/Co superlattices." Applied Surface Science 254, no. 1 (2007): 375–377.
Abstract: We study the superconducting and magnetic behaviour of Nb/Co superlattices, for superconducting Nb layer thickness of 44 nm and Co layer thickness less than 1 nm. In this limit no ferromagnetism is observed for Co. The superlattice behaves as independent superconducting Nb layers. We obtain the penetration depth and superconducting gap of the material, and analyze the results in terms of microscopic models and theories. (C) 2007 Elsevier B.V. All rights reserved.
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Monton, C., F. de la Cruz, and J. Guimpel. "Magnetic behavior of superconductor/ferromagnet superlattices." PHYSICAL REVIEW B 75, no. 6 (2007).
Abstract: A study of the electromagnetic response of superconductor/ferromagnet Nb/Co superlattices is presented. The dc magnetization is measured as a function of Co layer thickness, applied field H-a, and temperature. For very thin Co layers, no ferromagnetism is detected and the observed response is essentially that of a collection of uncoupled Nb layers. When the Co layer is thick enough for ferromagnetism to be established, prior to the field-cooled magnetization measurements, the Co layers are magnetically saturated in the parallel or antiparallel directions to H-a. In this case, the magnetic response of the otherwise uncoupled Nb layers is found to depend on both H-a and the stray fields.
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Bressan, O. J., A. E. Ridner, and F. de la Cruz. "T^5 law and Matthiessen's rule." Journal of Physics F: Metal Physics 5, no. 3 (1975): 481.
Abstract: Precise electrical resistivity measurements on very dilute non magnetic indium alloys show no doubt in a T 5 dependence on temperature between 1-4K and strong deviations from Matthiessen rule. Measurements of thermal resistivity show that the extrapolation method to obtain the data to H=0 is correct. Comparison of the results with recent theories is discussed.
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Guimpel, J., M. E. de la Cruz, F. de la Cruz, H. J. Fink, O. Laborde, and J. C. Villegier. "Size dependence of the Superconducting critical temperature and fields of Nb/Al multilayers." Journal of Low Temperature Physics 63, no. 1-2 (1986): 151–165.
Abstract: The critical temperatureT cof Nb/Al multilayers decreases as the total sample thicknessd Tis decreased while the thickness of each Nb and Al layer is kept constant. To understand this behavior, models based on the proximity effect and on weak two-dimensional (2D) localization are employed. The latter uses a characteristic length, the thermal diffusion length, in relation tod Tto obtain 2D behavior and leads to a reasonable explanation ofT c(d T). It is also found that the slope atT c(d T) of the critical magnetic field perpendicular to the layers is independent ofd Twhen the Nb and Al layer thicknesses are kept constant. The angular dependence of the critical field is also measured.
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Bridoux, G., G. Nieva, and F. de la Cruz. "Phase-coherence effects in vortex transport entropy." PHYSICAL REVIEW LETTERS 101, no. 11 (2008): 117002.
Abstract: Nernst and electrical resistivity measurements in superconducting YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+delta with and without columnar defects show a distinctive thermodynamics of the respective liquid vortex matter. At a field-dependent high temperature region in the H-T phase diagram, the Nernst signal is independent of structural defects in both materials. At lower temperatures, in YBa2Cu3O7-delta, defects contribute only to the vortex mobility, and the transport entropy is that of a system of vortex lines. The transition to lower temperatures in Bi2Sr2CaCu2O8+delta has a different origin; the maximum in the Nernst signal when decreasing temperature is not associated with transport properties but with the entropy behavior of pancake vortices in the presence of structural defects.
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Bridoux, G., P. Pedrazzini, F. de la Cruz, and G. Nieva. "Angular field dependence of the Nernst effect in Bi2Sr2CaCu2O8+delta." PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460 (2007): 841–842.
Abstract: The anomalous Nernst effect in hole-doped cuprates has been interpreted in terms of the existence of a superconducting order parameter well above the transition temperature, T-c(H). In order to improve the understanding of this problem, we have measured the angular field dependence of the Nernst signal in Bi2Sr2CaCu2O8+delta single crystals. The experiment was done tilting the magnetic field with respect to the direction of the temperature gradient, above and below T,(H), with applied fields up to 16 T. We have found that all the curves are scaled on one curve against the reduced field Hcos theta at a fixed temperature. (c) 2007 Elsevier B.V. All rights reserved.
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