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Author Conte, V.; Giordano, J.L.; Zarate, J.J.; Luzuriaga, J.
Title Superconducting Devices for Radioastronomy; First Steps in Chile: SNS-junction Fabrication Type Conference Article
Year 2010 Publication Abbreviated Journal
Volume 1 Issue Pages (down) 424-427
Keywords
Abstract We present results of the microfabrication of Josephson Junctions (JJs) of Superconductor-Normal-superconductor (SNS) type, as a first step in the acquisition of the know-how of superconducting devices applied to radioastronomy. A twojunction SQUID was built using a Nb/Al bilayer deposited on a Si wafer. The procedure needs only one mask and a single UV exposure (i.e., one photolithography step). We show the micrograph and the observed non linear characteristic I-V curve at 4K of the first device fabricated in the framework of ALMA Grant 31090010.
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Area Expedition Conference Twenty-First International Symposium on Space Terahertz Technology
Notes Approved no
Call Number BT @ pedrazp @ Serial 736
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Author Núñez Regueiro, M.; Esquinazi, P.; Izbizky, M.A.; Durán, C.; Castello, D.; Luzuriaga, J.
Title Tunneling systems in high temperature superconductors Type Journal Article
Year 1988 Publication Annales de Physique Abbreviated Journal Ann. Phys. Fr.
Volume 13 Issue 5 Pages (down) 401-406
Keywords acoustic wave absorption; acoustic wave velocity; barium compounds; high temperature superconductors; lanthanum compounds; rare earth compounds; strontium compounds; superconductive tunnelling; thermal conductivity of solids; tunnelling systems; high temperature superconductors; thermal conductivity; sound attenuation; sound velocity; model; low temperature specific heat; La Sr Cu O
Abstract We have measured the thermal conductivity, sound attenuation and relative variation of sound velocity of compounds of the La-Sr-Cu-O and RBa2Cu3O7 families, where R is a rare-earth. We have found that all these properties can be quantitatively correlated within a tunneling system model similar to that used in amorphous materials. This interpretation would naturally explain the anomalous linear term of the low temperature specific heat observed in these materials.
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ISSN 0003-4169 ISBN Medium
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Notes ISI:A1988Q715000009 Approved no
Call Number BT @ hernan @ Serial 264
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Author Civale, L.; de la Cruz, F.; Luzuriaga, J.
Title Critical temperature and density of states in amorphous Zr70Cu30 Type Journal Article
Year 1983 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 48 Issue 4 Pages (down) 389-391
Keywords ZIRCONIUM COPPER ALLOYS
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.
Address Centro Atomico Bariloche
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ISSN 00381098 (ISSN) ISBN Medium
Area Expedition Conference
Notes Cited By (since 1996): 1; Export Date: 28 April 2009; Source: Scopus; CODEN: SSCOA; Language of Original Document: English; Correspondence Address: Civale, L.; Centro At Approved no
Call Number BT @ luzuriag @ Serial 503
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Author Giordano, J.L.; Luzuriaga, J.; Badía-Majós, A.; Nieva, G.; Ruiz-Tagle, I. A.
Title Magnetization collapse in polycrystalline YBCO under transport current cycles Type Journal Article
Year 2006 Publication Superconducting Science and Technology Abbreviated Journal Supercond. Sci. Technol.
Volume 19 Issue 4 Pages (down) 385-391
Keywords
Abstract We report measurements of the hysteretic magnetization of YBCO under superimposed transport current cycles, together with numerical simulations of magnetization and current density profiles in the corresponding parallel configuration. Field cooled (FC) and zero-field-cooled (ZFC) experiments were carried out on polycrystalline YBa2Cu3O7?x cylinders, with both the applied magnetic field and transport current in the axial direction, and the current cycled several times, around and above the dissipative threshold. As in previously reported multicomponent field configuration experiments, the magnetization is seen to collapse to a more stable state both in FC and ZFC, because of the interplay between the shielding and transport currents. The results of our numerical simulations are in good qualitative agreement with the measurements, and the competition between shielding and transport due to vortex-pinning interactions and equilibrium magnetization effects are shown to play an important role in the range of our experiments.
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ISSN 0953-2048 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ gnieva @ Serial 467
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Author Rodríguez, E.; Duran, C.; Luzuriaga, J.; de la Cruz, F.; Fainstein, C.
Title Anomalous behaviour of the vortex structure in Bi4Ca2Sr4Cu4O16+y measured with a vibrating reed at low magnetic fields Type Journal Article
Year 1990 Publication Physica C: Superconductivity Abbreviated Journal Physica C
Volume 165 Issue 3-4 Pages (down) 315-320
Keywords
Abstract The response of the vortex structure in ceramic samples of Bi4Ca2Sr4Cu4O16+y has been measured by means of a vibrating reed technique in magnetic fields below 0.2 T. An anomally in the response of the reed is seen at temperatures of around 30 to 40 K, well below the critical temperature, indicating a transition similar to that attributed to a melting of the Flux Line Lattice. There is a shift in the temperature at which the anomaly is detected when one increases the driving force on the reed, while the dissipation shows a maximum associated to the transition which scales with the square of the applied magnetic field. Comparison with magnetization measurements shows that there is non-zero critical current at the same temperature where the anomalous behaviour is detected with our technique.
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ISSN 0921-4534 ISBN Medium
Area Expedition Conference
Notes ISI:A1990CN49800014 Approved no
Call Number BT @ hernan @ Serial 261
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Author Zemma, E.; Tsubota, M.; Luzuriaga, J.
Title Possible visualization of a superfluid vortex loop attached to an oscillating Beam Type Journal Article
Year 2015 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 179 Issue 5 Pages (down) 310-319
Keywords Quantum fluids; Superfluid helium; Flow visualization; Vortex loops
Abstract Visualization using tracer particles is a relatively new tool available for the study of superfluid turbulence and flow, which is applied here to oscillating objects submerged in the liquid. We report observations of a structure seen in videos taken from outside a cryostat filled with superfluid helium at 2 K, which is possibly a vortex loop attached to an oscillator. The feature, which has the shape of an incomplete arch, is visualized due to the presence of solid H2 tracer particles and is attached to a beam oscillating at 38 Hz in the liquid. It has been recorded in videos taken at 240 frames per second, fast enough to take ∼6 images per period. This makes it possible to follow the structure, and to see that it is not rigid. It moves with respect to the oscillator, and its displacement is in phase with the velocity of the moving beam. Analyzing the motion, we come to the conclusion that we may be observing a superfluid vortex attached to the beam and decorated by the hydrogen particles. An alternative model, considering a solid hydrogen filament, has also been analyzed, but the observed phase between the movement of the beam and the filamentary structure is better explained by the superfluid vortex hypothesis.
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Notes Approved no
Call Number BT @ pedrazp @ Serial 734
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Author Ceva, H.; Luzuriaga, J.
Title Correlations in the sand pile model: From the log-normal distribution to self-organized criticality Type Journal Article
Year 1998 Publication Physics Letters A Abbreviated Journal Phys. Lett. A
Volume 250 Issue 4-6 Pages (down) 275-280
Keywords
Abstract We have studied the approach of the Abelian sand pile model towards the stationary, self-organized criticality state. The uncorrelated limit is shown both numerically and by a simple analysis to follow the log-normal distribution. We introduce and evaluate several correlation functions to study the correlated region.
Address Ctro. Atom. Bariloche Inst. Balseiro, CNEA, UNC, 8400 Bariloche, Argentina
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ISSN 03759601 (ISSN) ISBN Medium
Area Expedition Conference
Notes Cited By (since 1996): 2; Export Date: 28 April 2009; Source: Scopus; CODEN: PYLAA; Language of Original Document: English; Correspondence Address: Ceva, H.; Departamento de F Approved no
Call Number BT @ luzuriag @ Serial 479
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Author Luzuriaga, J.
Title Measurements in the laminar and turbulent regime of superfluid4He by means of an oscillating sphere Type Journal Article
Year 1997 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 108 Issue 3-4 Pages (down) 267-277
Keywords Calculations; Laminar flow; Oscillations; Spheres; Turbulence; Turbulent flow; Vibrations (mechanical); Oscillating sphere; Translational oscillation; Superfluid helium
Abstract The translational oscillations of a sphere in liquid helium have been measured as a way of studying superfluid turbulence. Experiments were carried out in the laminar flow regime for reference purposes, and good agreement found between measured and calculated quantities. In the turbulent region, the dissipation is found to be proportional to the square of the velocity of the sphere, as found previously by other workers. For high vibration amplitudes there is an increase in the hydrodynamic mass. This seems to scale with the superfluid fraction in a way that strongly suggests that the superfluid component plays an important role in the turbulent regime.
Address Comisi
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ISSN 00222291 (ISSN) ISBN Medium
Area Expedition Conference
Notes Cited By (since 1996): 2; Export Date: 28 April 2009; Source: Scopus; CODEN: JLTPA; Language of Original Document: English; Correspondence Address: Luzuriaga, J.; Comisi Approved no
Call Number BT @ luzuriag @ Serial 518
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Author Luzuriaga, J.
Title Sphere on a vibrating reed for measurements of turbulence in superfluid helium Type Journal Article
Year 2000 Publication Journal of Alloys and Compounds Abbreviated Journal J Alloys Compd
Volume Issue Pages (down) 265-268
Keywords Cantilever beams; Computational methods; Laminar flow; Oscillators (electronic); Phase transitions; Turbulent flow; Vibrations (mechanical); Oscillating spheres; Spherical geometries; Vibrating reeds; Superfluid helium
Abstract A modification of the vibrating reed, in which a massive sphere is made to oscillate at the end of a cantilevered beam, has been used for measurements in superfluid helium. The apparatus operates in the same way as a conventional vibrating reed with capacitive detection and drive. However, when operating submerged in the liquid, the frequency changes give information on the superfluid fraction, and the dissipation can be used to obtain information on the change of liquid flow, from laminar to turbulent. The spherical geometry allows an exact calculation of all parameters in the laminar regime, so departures due to the turbulence can be better quantified. The method has been found to work well in practice, and some measurements on the turbulent regime in the superfluid are presented.
Address Centro At
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Publisher Elsevier Sequoia SA Place of Publication Buenos Aires, Argent Editor
Language Summary Language Original Title
Series Editor Series Title 12th International Conference on Internal Friction and Ultrasonic Attenuation in Solids (ICIFUAS-12) Abbreviated Series Title
Series Volume 310 Series Issue 1-2 Edition
ISSN 09258388 (ISSN) ISBN Medium
Area Expedition Conference
Notes Conference code: 57483; Export Date: 28 April 2009; Source: Scopus; CODEN: JALCE; doi: 10.1016/S0925-8388(00)00962-2; Language of Original Document: English; Correspondence Address: Luzuriaga, Javier; Centro Atomico Bariloche Bariloche, Argentina; Sponsors: ABDUS SALAM International Centre for Theoretical Physics; Centre for Industrial Research (CINI); Comision Nacional de Actividades Espaciales (CONAE) Approved no
Call Number BT @ luzuriag @ Serial 478
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Author Luzuriaga, J.; Andre, M.-O.; Benoit, W.
Title Frequency and amplitude response of the flux-line lattice to mechanical perturbation in ceramic YBa2Cu3O7 Type Journal Article
Year 1992 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 201 Issue 3-4 Pages (down) 257-262
Keywords Copper oxides; Crystal lattices; Frequency response; Internal friction; Lattice vibrations; Magnetic fields; Mathematical models; Mechanical properties; Pendulums; Rheology; Thermal effects; Torque; Yttrium compounds; Amplitude response; Ceramic yttrium barium copper oxides; Extended dry friction model; Flux line lattices; Forced pendulum; Frequency independent dissipation peak; Mechanical response; Thermal activation; High temperature superconductors
Abstract The mechanical response of the flux-line lattice has been measured with a low-frequency forced pendulum in ceramic YBa2Cu3O7. A dissipation peak observed in temperature sweeps is frequency-independent between 1 mHz and 5 Hz. Dissipation depends strongly on applied torque, and for fixed temperatures this dependence is well fitted by a rheological model of extended dry friction. If the model is extended to take account of thermal activation, however, it does not agree with the measured frequency independence, which is hard to explain within simple models of thermal activation.
Address Institut de G
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN 09214534 (ISSN) ISBN Medium
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Notes Export Date: 28 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Luzuriaga, J.; Institut de G Approved no
Call Number BT @ luzuriag @ Serial 487
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