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Author (up) André, M-O.; Polichetti, M.; Pastoriza, H.; Kes, P. H. doi  openurl
  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 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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  Call Number BT @ hernan @ andre99 Serial 2  
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Author (up) Correa, V.F.; Herbsommer, J.A.; Kaul, E.E.; de la Cruz, F.; Nieva, G. openurl 
  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 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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  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 (up) Decca, R.S.; Drew, H.D.; Osquiguil, E.; Maiorov, B.; Guimpel, J. openurl 
  Title Anomalous proximity effect in underdoped YBa2Cu3O6+x Josephson junctions Type Journal Article
  Year 2000 Publication Physical Review Letters Abbreviated Journal Phys Rev Lett  
  Volume 85 Issue 17 Pages 3708-3711  
  Keywords Critical currents; Energy gap; High temperature superconductors; Magnetic field effects; Magnetron sputtering; Mathematical models; Phase diagrams; Phase transitions; Physical properties; Scanning electron microscopy; Superconductivity; Yttrium barium copper oxides; Anomalous proximity effect; Fluctuating phase models; Josephson effect; Photodoping; Josephson junction devices  
  Abstract Experiments were carried out to probe the underdoped insulating material by the Josephson effect. Junctions were fabricated by exploiting the capability of locally photodoping insulating RBa2Cu3O6+x (R = rare earth) material. The existence of an anomalously large proximity effect was confirmed. The critical current of the junctions was consisted with the conventional Josephson relationship.  
  Address Centro At  
  Corporate Author Thesis  
  Publisher American Inst of Physics Place of Publication Woodbury, NY, United States Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 00319007 (ISSN) ISBN Medium  
  Area Expedition Conference  
  Notes Cited By (since 1996): 36; Export Date: 17 April 2009; Source: Scopus; CODEN: PRLTA; doi: 10.1103/PhysRevLett.85.3708; Language of Original Document: English; Correspondence Address: Decca, R.S.; Univ of Maryland College Park, United States; References: Ginsberg, D.M., (1996) Physical Properties of High Temperature Superconductors V, , World Scientific, Singapore; Zhang, S.C., (1997) Science, 275, p. 1089; Emery, V.J., Kivelson, S.A., (1995) Nature (London), 374, p. 434; Corson, J., (1999) Nature (London), 398, p. 291; Renner, Ch., (1998) Phys. Rev. Lett., 80, p. 149; Demler, E., (1998) Phys. Rev. Lett., 80, p. 2917; Den Hertog, B.C., Berlinsky, A.J., Kallin, C., (1999) Phys. Rev. B, 59, pp. R11645; Emery, V.J., Kivelson, S.A., Zachar, O., (1997) Phys Rev. B, 56, p. 6120; Tinkham, M., (1996) Introduction to Superconductivity, , McGraw-Hill, New York; Decca, R.S., (1998) Appl. Phys. Lett., 73, p. 120; (1999) J. Microsc., 194, p. 407; Osquiguil, E., (1992) Appl. Phys. Lett., 60, p. 1627; Kudinov, V.I., (1993) Phys. Rev. B, 47, p. 9017; Decca, R.S., Drew, H.D., Empson, K.L., (1997) Appl. Phys. Lett., 70, p. 1932; Orenstein, J., (1990) Phys. Rev. B, 42, p. 6342; Nieva, G., (1992) Appl. Phys. Lett., 60, p. 2159; (1992) Phys. Rev. B, 46, p. 14249; notenoteGray, K.E., (1992) Phys. Rev. B, 45, p. 10071; Pauza, A.J., (1997) J. Appl. Phys., 82, p. 5612; Katz, A.S., Woods, S.I., Dynes, R.C., (2000) J. Appl. Phys., 87, p. 2978; noteUR – http://www.scopus.com/scopus/inward/record.url?eid=2-s2.0-19244384844&partnerID=40 Approved no  
  Call Number BT @ osquigui @ Serial 373  
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Author (up) Fainstein, A.; Maiorov, B.; Guimpel, J.; Nieva, G.; Osquiguil, E. url  openurl
  Title Annealing disorder and photoinduced order of oxygen chains in detwinned YBa2Cu3O6.65 single crystals probed by Raman scattering Type Journal Article
  Year 2000 Publication Physical Review B – Condensed Matter and Materials Physics Abbreviated Journal Phys. Rev. B Condens. Matter Mater. Phys.  
  Volume 61 Issue 6 Pages 4298-4304  
  Keywords  
  Abstract Raman scattering in detwinned YBa2Cu3O6.65 single crystals is studied as a function of photoexcitation and annealing. Copper-oxygen chain-related forbidden Raman bands that are known to strongly bleach with illumination at low temperatures, increase their intensity with chain fragmentation induced by annealing at high temperature. This contrasting behavior proves the conjunction of short Cu-O fragments into longer chains on photoexcitation. We interpret the Raman modes as due to vibrations at the end of CuO chain fragments and Cu-O-Cu monomers, and use their evolution with illumination and annealing as anisotropic sensitive markers of oxygen reordering processes. The identification of the “forbidden” Raman bands is discussed in the context of our results and recent literature in the subject. We also present absorption measurements performed on GdBa2Cu3Ox thin films with varying oxygen content. These experiments show that the 2.2-eV absorption and the chain-related Raman peaks have different dependencies with oxygen content and illumination, ruling out an explanation that suggests that the Raman intensity reduction of these modes is due to a photobleaching of intermediate defect states. These results highlight the potentialities of Raman scattering for oxygen dynamics studies and demonstrate the presence of photoinduced oxygen ordering in these high-Tc superconductor compounds.  
  Address Centro At  
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  Series Volume Series Issue Edition  
  ISSN 01631829 (ISSN) ISBN Medium  
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  Notes Cited By (since 1996): 18; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Fainstein, A.; Centro At Approved no  
  Call Number BT @ osquigui @ Serial 374  
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Author (up) Fasano, Y.; Menghini, M.; de la Cruz, F.; Nieva, G. openurl 
  Title Weak interaction and matching conditions for replicas of vortex lattices Type Journal Article
  Year 2000 Publication PHYSICAL REVIEW B Abbreviated Journal  
  Volume 62 Issue 22 Pages 15183-15189  
  Keywords  
  Abstract We present experiments demonstrating the conditions under which weak interaction between replicas of vortex structures break their translational and rotational symmetry. The Fe clumps introduced by Bitter decorations of vortex structures are used to induce an extremely weak interaction fur subsequent vortex structures in low and high temperature superconducting crystals. The matching between the Fe pattern acid the vortex configuration require the structure to be prepared under quite stringent conditions: The field creating the structure has to be the same in magnitude although it can differ in orientation from that used for the preparation of the Fe pattern. The interaction between vortex replicas as represented by the Fe clumps of Bitter decorations makes it possible to differentiate the vortex nucleation and propagation mechanisms in low and high temperature superconductors.  
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  ISSN 0163-1829 ISBN Medium  
  Area Expedition Conference  
  Notes ISI:000165883800075 Approved no  
  Call Number BT @ hernan @ Serial 219  
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Author (up) Herbsommer, J.A.; Nieva, G.; Luzuriaga, J. doi  openurl
  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 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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  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 (up) Herbsommer, J.A.; Nieva, G.; Luzuriaga, J. doi  openurl
  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 Physical Review B Abbreviated Journal Phys. Rev. B  
  Volume 62 Issue 5 Pages 3534-3541  
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  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  
  Area Expedition Conference  
  Notes ISI:000088714200086 Approved no  
  Call Number BT @ hernan @ Serial 224  
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Author (up) Herbsommer, J.A.; Nieva, G.; Luzuriaga, J. doi  openurl
  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 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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Author (up) Herbsommer, J.A.; Nieva, G.; Luzuriaga, J. openurl 
  Title Interaction of vortices with oriented twin boundaries in single-crystal YBa2Cu3O7-delta Type Journal Article
  Year 2000 Publication Physical Review B Abbreviated Journal Phys. Rev. B  
  Volume 61 Issue 17 Pages 11745-11751  
  Keywords  
  Abstract We have studied the response of the vortex lattice (VL) in a YBa2Cu3O7-delta sample with oriented twin boundaries (TB's) and in an untwinned sample. In the twinned sample the density of twin boundaries is estimated from decoration experiments. The TB's affect the liquid-to-solid transition in the vortex structure, which is of first order in the twin free crystal and to a Bose glass in the twinned sample. We measure the ac susceptibility, and find that the response strongly depends on the orientation of the probing ac field with respect to the TB's. The ac field produces a tilting stress on the vortices. With the applied de magnetic field H-dc parallel to the c axis, the response of the VL is weaker when the tilt is parallel to the TB's than when it is perpendicular or at 45 degrees to the TB's. The results are explained by the fact that the VL is locked to the twin boundaries for small deviations of H-dc from the c axis and is partially pinned to them for larger angles. By measuring over the whole angular range we estimate the angles over which each regime is realized for different temperatures. The results of the detwinned sample are used for comparison.  
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  Series Volume Series Issue Edition  
  ISSN 1098-0121 ISBN Medium  
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  Notes ISI:000086937700090 Approved no  
  Call Number BT @ hernan @ Serial 228  
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Author (up) Herbsommer, Juan A. openurl 
  Title Dinámica y estática de vórtices en superconductores de alta temperatura crítica con defectos correlacionados Type Book Whole
  Year 2000 Publication Abbreviated Journal  
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  Address Instituto Balseiro  
  Corporate Author Thesis Ph.D. thesis  
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  Notes Approved no  
  Call Number BT @ hernan @ Serial 328  
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