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Author Rodriguez, D.S.; Rodriguez, E.; Luzuriaga, J.; Waszczak, J.V.; Cheong, S.W.
Title Role of anisotropy in the vortex lattice of superconductors high-Q oscillator measurements in 2H-NbSe2 and La1.825Sr.075CuO4 Type Journal Article
Year 1994 Publication (up) Physica C Abbreviated Journal
Volume 229 Issue 1-2 Pages 59-64
Keywords
Abstract Measurements of the response of the flux-line lattice in NbSe2 and La1.825Sr0.075CuO4 show important differences between these two materials. In particular, we have studied the magnetic-field and angular dependence of the response of a high-Q mechanical oscillator in fields of up to 1 T. The features seen in NbSe2 seem to be well explained in terms of a change in the pinning regime, usually termed the ''peak effect'' in the critical current, using the collective-pinning model of Larkin and Ovchivnikov within Ginzburg-Landau anisotropic theory. On the other hand the behavior found in the high-T(c) material LSCO seems to fall naturally into a description which takes into account the possibility of phase transitions in the vortex lattice and the quasi-two-dimensional character of the superconductivity.
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ISSN 0921-4534 ISBN Medium
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Notes ISI:A1994PF49500008 Approved no
Call Number BT @ hernan @ Serial 252
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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 (up) Physica C Abbreviated Journal Physica C
Volume 341 Issue Pages 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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ISSN 0921-4534 ISBN Medium
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Notes ISI:000165855700143 Approved no
Call Number BT @ hernan @ Serial 220
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Author Herbsommer, J.A.; Luzuriaga, J.; Cheong, S.-W.
Title Vortex glass melting in single crystal La1.825 Sr0.075CuO4 Type Journal Article
Year 1996 Publication (up) Physica C Abbreviated Journal Physica C
Volume 258 Issue 1-2 Pages 169-174
Keywords Copper compounds; Crystal lattices; Frequency response; Glass; Magnetic field measurement; Magnetic permeability measurement; Melting; Phase diagrams; Single crystals; Temperature; Vortex flow; AC susceptibility; Cuprates; Pinned flux lattice; Oxide superconductors
Abstract The vortex phase diagram in single crystalline La1.85Sr0.075CuO4 has been studied using an AC-susceptibility technique. A peak in the out-of-phase (x?) component of the susceptibility indicates a transition from a pinned flux lattice (FLL) to an unpinned one. This peak is frequency dependent for all the values of the magnetic field measured (0.01 to 4 T), and this, as well as the general behavior found in the cuprates, has prompted us to interpret our data as evidence for a vortex-glass to liquid transition in the FLL. The activation energies obtained can be fitted to a theory developed by Vinokur et al. Measurements with the magnetic field at an angle with the Cu-O planes may also be understood qualitatively within this framework.
Address AT and T Bell Laboratories, Murray Hill, NJ, United States
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Notes Cited By (since 1996): 2; Export Date: 28 April 2009; Source: Scopus; CODEN: PHYCE; doi: 10.1016/0921-4534(95)00812-8; Language of Original Document: English; Correspondence Address: Luzuriaga, J.; Centro At Approved no
Call Number BT @ luzuriag @ Serial 483
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Author Herbsommer, J.A.; Luzuriaga, J.; Civale, L.; Nieva, G.; Pasquini, G.; Lanza, H.; Levy, P.
Title Angular variation of pinning near the irreversibility temperature in single crystal Y Ba2Cu3O7-? with splayed columnar defects Type Journal Article
Year 1998 Publication (up) Physica C Abbreviated Journal Physica C
Volume 304 Issue 1-2 Pages 112-118
Keywords Columnar defects; Critical current density; Flux pinning; Pinning force; Anisotropy; Critical current density (superconductivity); Crystal defects; Single crystals; Columnar defects; Flux pinning; Yttrium barium copper oxides
Abstract We have studied vortex pinning through ac susceptibility measurements in single crystals of YBCO with columnar defects (CDs). The CDs have 0, 10 and 20 splay angle and average direction 108 off the c-axis. By studying the angular variation we can compensate for the anisotropy and effects of twins, etc. Using a simple expression we can obtain the angular spread when the field direction is outside the splay angle. An increase of pinning when the field direction is inside

the angle defined by the CDs can be attributed to vortex entanglement due to the splay and the suppression of the sliding of double kinks.
Address Departamento de F
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Notes Cited By (since 1996): 10; Export Date: 28 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Herbsommer, J.A.; Ctro. Atom. Bariloche Inst. Balseiro; CNEA and UNC 8400 Bariloche, Argentina; References: Civale, L., Marwick, A.D., Worthington, T.K., Kirk, M.A., Thompson, J.R., Krusin-Elbaum, L., Sun, Y., Holtzberg, F., (1991) Phys. Rev. Lett., 67, p. 648; Hwa, T., Doussal, P.L., Nelson, D.R., Vinokur, V.M., (1993) Phys. Rev. Lett., 71, p. 3545; Civale, L., Krusin-Elbaum, L., Thompson, J.R., Wheeler, R., Marwick, A.D., Kirk, M.A., Sun, Y.R., (1994) Phys. Rev. B, 50, p. 4102; Krusin-Elbaum, L., Thompson, J.R., Wheeler, R., Marwick, A.D., Li, C., Patel, S., Shaw, D.T., Ullmann, J., (1994) Appl. Phys. Lett., 64, p. 3331; Hardy, V., Whal, A., Hebert, S., Ruyler, A., Provost, J., Groult, D., Simon, C., (1996) Phys. Rev. B, 54, p. 656; Hardy, V., Ruyter, A., Whal, A., Maignan, A., Groult, D., Provost, J., Simon, C., Noel, H., (1996) Physica C, 257, p. 16; Krusin-Elbaum, L., Marwick, A.D., Wheeler, R., Feild, C., Vinokur, V.M., Leaf, G.K., Palumbo, M., (1996) Phys. Rev. Lett., 76, p. 2563; Prozorov, R., Konczykowski, M., Schmidt, B., Yeshurun, Y., Shaulov, A., Villard, C., Koren, G., (1996) Phys. Rev. B, 54, p. 15530; De La Cruz, F., L Approved no
Call Number BT @ luzuriag @ Serial 517
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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 (up) Physica C: Superconductivity Abbreviated Journal Physica C
Volume 165 Issue 3-4 Pages 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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Notes ISI:A1990CN49800014 Approved no
Call Number BT @ hernan @ Serial 261
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Author Safar, H.; Durán, C.; Guimpel, J.; Civale, L.; Luzuriaga, J.; Rodríguez, E.; de la Cruz, F.; Fainstein, C.; Schneemeyer, L.F.; Waszczak, J.V.
Title Logarithmic to nonlogarithmic flux creep transition and magnetic flux hardening in BiSrCaCuO superconducting ceramics Type Journal Article
Year 1989 Publication (up) Physica C: Superconductivity Abbreviated Journal
Volume 162-164, Part 1 Issue Pages 665-666
Keywords
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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ISSN 0921-4534 ISBN Medium
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Notes Approved no
Call Number BT @ jguimpel @ Serial 626
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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 (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 201 Issue 3-4 Pages 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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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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Author Núñez Regueiro, M.; Esquinazi, P.; Izbizky, M.A.; Duran, C.; Castello, D.; Luzuriaga, J.; Nieva, G.
Title Evidence of tunneling systems through thermal and acoustic measurements in ceramic materials Type Journal Article
Year 1988 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Physica C
Volume 153-155 Issue PART 2 Pages 1016-1017
Keywords Acoustic Variables Measurement--Wave Velocity; Ceramic Materials--Thermal Conductivity; Europium Barium Copper Oxides; Superconducting Materials
Abstract We have neasured the sound velocity, internal friction, thermal conductivity and specific heat of La-based and (Y/Eu)- based ceramics. The low temperature data can be understood in terms of the Tunneling Model assuming the existence of Tunneling Systems (TS). From these measured properties we obtain values for the parameter C=P?2/?v2, where P is the density of states of TS, ? the coupling constant between phonons and TS, ? the mass density and v the sound velocity close to those obtained for amorphous and “orientational” disordered crystalline materials. Our data would indicate that the TS are intrinsic defects independent of the sample porosity.
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Area Expedition Conference International Conference on High Temperature Superconductors and Materials and Mechanisms of Superconductivity
Notes Export Date: 28 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Regueiro, M.N.; Centro At Approved no
Call Number BT @ luzuriag @ Serial 496
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Author Herbsommer, J.A.; Nieva, G.; Luzuriaga, J.
Title Interplay between pinning energy and vortex interaction in YBa2Cu3O7-delta with oriented twin boundaries in tilted magnetic fields: Bitter decoration and tilt-modulus measurements Type Journal Article
Year 2000 Publication (up) Physical Review B Abbreviated Journal Phys. Rev. B
Volume 62 Issue 5 Pages 3534-3541
Keywords
Abstract We have performed Bitter decoration and ac susceptibility measurements in single-crystal YBa2Cu3O7-delta with oriented twin boundaries. The twin boundaries (TB's) pin vortices over approximately 65% of the sample. The pinned areas are unevenly distributed and some relatively large TB-free regions are present. The Bitter decorations were performed in a 52 Oe de magnetic field rotated off the c axis so that the plane defined by the field direction and the c axis is perpendicular to the TB's. Several decorations were performed in the same sample. Additional dynamical information was obtained from ac susceptibility measurements. Results show that for small tilts the vortices remain locked to the c-axis direction, for angles greater than 12 degrees they form a staircase pattern, and in this case pinning by the twin boundaries remains effective up to 75 degrees. We observe vortex chains in twin-free-zones of the sample for tilted fields at 65 degrees and 40 degrees. Due to our particular experimental arrangement, in the twinned regions the interplay of the potentials giving rise to the chains and the pinning potential produces a structure with a disordered square symmetry. The data allow us to estimate the dominant energy of the vortex system for some inclinations of the applied magnetic field.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:000088714200086 Approved no
Call Number BT @ hernan @ Serial 224
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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 (up) Physical Review B Abbreviated Journal Phys. Rev. B
Volume 62 Issue 1 Pages 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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ISSN 0163-1829 ISBN Medium
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Notes ISI:000088037000106 Approved no
Call Number BT @ hernan @ Serial 225
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