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Author Kaul, E.E.; Nieva, G.
Title Oxygen doping effects on the magnetization of Bi2Sr2CaCu2O8+delta single crystalline system in the mixed state Type Journal Article
Year 2000 Publication PHYSICA C Abbreviated Journal
Volume 341 Issue Pages (down) 1343-1344
Keywords
Abstract We present a systematic study of the oxygen overdoping effects on the de magnetization loops of Bi2Sr2CaCu2O8+delta single crystalline samples. The overdoping is produced by high oxygen pressure (from 1 to 190 bar) annealing at 500 degreesC. The super conducting critical temperature and the c-axis lattice parameter are used to identify the oxygen content of the samples. The dc magnetization loop measurements are performed with the applied magnetic field parallel to the c-axis of the crystals. The characteristic second peak in the magnetization is present far all the investigated oxygen contents. We show that the position of this second peak and the irreversibility field increase monotonically as a function of oxygen doping.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0921-4534 ISBN Medium
Area Expedition Conference
Notes ISI:000165855700271 Approved no
Call Number BT @ hernan @ Serial 222
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Author Correa, V.F.; Herbsommer, J.A.; Kaul, E.E.; de la Cruz, F.; Nieva, G.
Title Onset of the 0-dimensional vortex pinning behavior in the optimally doped and overdoped Bi2Sr2CaCu2O8+delta system Type Journal Article
Year 2000 Publication PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Abbreviated Journal
Volume 341 Issue Pages (down) 1285-1286
Keywords
Abstract We report results of transverse AC magnetic permeability in the linear regime and DC magnetization loops for optimally doped and oxygen overdoped samples of Bi2Sr2CaCu2O8+delta The data cover the low temperature (T < 25K) and low held (H-a < 1000 Oe) region of the magnetic (H-a-T) phase diagram. In optimally doped as well as in overdoped samples a crossover to a O-dimensional pinning regime (Larkin length, L-C(C), shorter than the inter-plane CuO2 distance) is observed at a characteristic temperature Too for all investigated fields. The order-disorder transition, identified by the second peak in magnetization and a non monotonous field dependence of the AC penetration depth, is quenched below T-0D.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0921-4534 ISBN Medium
Area Expedition Conference
Notes ISI:000165855700242 Approved no
Call Number BT @ hernan @ Serial 221
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Author Silhanek, K.; Guimpel, J.; Civale, L.; Lanza, H.; Levy, P.
Title Thickness effects on the pinning by columnar defects Type Journal Article
Year 2000 Publication PHYSICA C Abbreviated Journal
Volume 341 Issue Pages (down) 1217-1218
Keywords
Abstract We compare the angular dependence of the pinning of equivalent columnar defects in GdBa2Cu2O7 thin films and a thicker YBa2Cu3O7 single crystal. The tracks' related enhancement of the critical currents is much smaller for the case of the thin films. We interpret this thickness dependence as resulting from a competition between the pinning of the correlated structures, related to total sample thickness, and surface boundary conditions, which force the vortices to depin from the columnar defects near the sample surface.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0921-4534 ISBN Medium
Area Expedition Conference
Notes ISI:000165855700208 Approved no
Call Number BT @ hernan @ Serial 175
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Author Herbsommer, J.A.; Nieva, G.; Luzuriaga, J.
Title Reproducibility of the disordered vortex structure in twinned single crystals of YBCO Type Journal Article
Year 2000 Publication Physica C Abbreviated Journal Physica C
Volume 341 Issue Pages (down) 1087-1088
Keywords
Abstract Bitter decorations of the vortices in twinned single crystal YBCO have been obtained to study the disordered structure formed on successive cooldowns of the sample under the same conditions of field and temperature. Between succesive decorations, the iron dots could be removed completely, giving a surface clean enough for further decoration. It was found that successive realizations of the disordered vortex state were very similar at long range, and differed mostly on short scales, compared to the average vortex separation. We have quantified the correlation between successive structures, and double sided decorations have been also performed to compare with the extent of spatial correlation in the applied field direction. The coincidence of the position of the vortices in successive realizations of the structure, is unexpected, and indicates an unusual behavior for a glassy system. Our technique makes it possible to image the position of the vortices in detail and repeatedly, providing us with a model amorphous system in which to study the reproducibility of the disordered structure.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0921-4534 ISBN Medium
Area Expedition Conference
Notes ISI:000165855700143 Approved no
Call Number BT @ hernan @ Serial 220
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Author Pastoriza, H.; Candia, S.; Nieva, G.
Title Anisotropic vortex dynamics in twined YBaCuO single crystals Type Journal Article
Year 2000 Publication Physica B Abbreviated Journal
Volume 284-288 Issue 2 Pages (down) 763-764
Keywords
Abstract Rotating continuously the applied vortex force and measuring the vortex velocity vector, we were able to directly determine the role of twin boundaries in the vortex dynamics in YBa$2$Cu$3Ο_7$ single crystals with unidirectional twins. We show the different effect of these correlated pinning defects into the various vortex phases. In the entangled vortex liquid state, we observe a linear response but with an anisotropic viscosity. On the other hand, an anomalous guided motion by twin planes is found in the vortex solid.
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Language Summary Language Original Title
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ISSN ISBN Medium
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Notes Approved no
Call Number BT @ hernan @ pastoriza00 Serial 39
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Author Herbsommer, J.A.; Nieva, G.; Luzuriaga, J.
Title Repetition of the disordered pattern in successive solidifications of vortex matter observed by Bitter decoration Type Journal Article
Year 2000 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 62 Issue 1 Pages (down) 678-681
Keywords
Abstract Repeated images of the vortex structure in YBa2Cu3O7-delta Single crystals have been obtained, using the Bitter technique. By removing the iron dots between each decoration experiment, it is possible to image the vortices in different cooldown runs done under the same field and temperature conditions. The images show that these different realizations of a disordered vortex state found in twinned crystals are very similar at long range and differ only in small-scale detail. This is unusual behavior in glassy systems, where expectations are that successive configurations will differ over many scales. In contrast, ordered vortex crystals in clean samples can form with different orientations in different runs, therefore differing at long ranges. Double-sided decorations have been performed in twinned samples, and the correlation between images in both sides of the sample is similar in magnitude but slightly different qualitatively than that found in successive decorations.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0163-1829 ISBN Medium
Area Expedition Conference
Notes ISI:000088037000106 Approved no
Call Number BT @ hernan @ Serial 225
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Author Sereni, J.G.
Title Evanescence of magnetic transitions in Ce systems Type Journal Article
Year 2000 Publication Physica B – Condensed Matter Abbreviated Journal Physica B
Volume 281-282 Issue Pages (down) 337-339
Keywords
Abstract Three types of magnetic phase diagrams can be identified in Ce systems: (I) with ordering temperature T-ord --> 0 continuously, followed by a narrow non-Fermi-liquid (NFL) region, (II) with T-ord vanishing at finite temperature, followed by an extended NFL region, and (III) where the degrees of freedom condensed into the ordered phase decreases, without a concomitant decrease of T-ord. Intrinsic differences are found in the way that the degrees of freedom condense at T-ord and from the rising of the specific heat tails above T-ord. (C) 2000 Elsevier Science B.V. All rights reserved.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0921-4526 ISBN Medium
Area Expedition Conference
Notes ISI:000086570200141 Approved no
Call Number BT @ hernan @ Serial 79
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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.
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Corporate Author Thesis
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 André, M-O.; Polichetti, M.; Pastoriza, H.; Kes, P. H.
Title Vortex dynamics in 2H-NbSe$_2$ containing a periodic channel structure Type Journal Article
Year 2000 Publication Physica C Abbreviated Journal
Volume 338 Issue Pages (down) 179-188
Keywords
Abstract We have measured the resistivity and magnetic AC susceptibility of 2H-NbSe single crystals containing alternating 2 stripes of irradiated and non-irradiated regions of columnar defects created by heavy-ion bombardment. Without applied magnetic field, the sample undergoes a double-step transition into the superconducting state, each step corresponding to the transitions in the irradiated and non-irradiated regions, respectively. For fields smaller than half of the matching field and upon increasing the temperature, the onset of flux motion in the non-irradiated channels occurs, when the applied stress due to the electrical current equals the shear stress at the channel edges, while depinning in the irradiated stripes occurs at higher temperature. The weak amplitude dependence of the shear process suggests that it takes place at the melting transition. We observed only a single-step transition at DC magnetic fields larger than half the matching field, because pinning by the columnar defects in the irradiated stripes is much less effective, and consequently the shear stress at the channel edges is strongly reduced. The comparison between the shear stress deduced from I curves and the theoretical value $?max = AC66$ yields a value for the constant Α, which is in good agreement with theoretical predictions.
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Notes Approved no
Call Number BT @ hernan @ andre99 Serial 2
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Author Jaime, M.; Movshovich, R.; Stewart, G.R.; Beyermann, W.P.; Berisso, M.G.; Hundley, M.F.; Canfield, P.C.; Sarrao, J.L.
Title Closing the spin gap in the Kondo insulator Ce3Bi4Pt3 at high magnetic fields Type Journal Article
Year 2000 Publication Nature Abbreviated Journal
Volume 405 Issue 6783 Pages (down) 160-163
Keywords
Abstract Kondo insulator materials(1)-such as CeRhAs, CeRhSb, YbB12, Ce3Bi4Pt3 and SmB6-are 3d, 4f and 5f intermetallic compounds that have attracted considerable interest in recent years(2-5). At high temperatures, they behave like metals. But as temperature is reduced, an energy gap opens in the conduction band at the Fermi energy and the materials become insulating. This contrasts with other f-electron compounds, which are metallic at all temperatures. The formation of the gap in Kondo insulators has been proposed to be a consequence of hybridization between the conduction band and the f-electron levels(6,7), giving a 'spin' gap. If this is indeed the case, metallic behaviour should be recovered when the gap is closed by changing external parameters, such as magnetic field or pressure. Some experimental evidence suggests that the gap can be closed in SmB6 (refs 5, 8) and YbB12 (ref. 9). Here we present specific-heat measurements of Ce3Bi4Pt3 in d.c. and pulsed magnetic fields up to 60 tesla. Numerical results and the analysis of our data using the Coqblin-Schrieffer model demonstrate unambiguously a field-induced insulator-to-metal transition.
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0028-0836 ISBN Medium
Area Expedition Conference
Notes ISI:000087080100043 Approved no
Call Number BT @ hernan @ Serial 300
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