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Author Sirena, M.; Steren, L.; Guimpel, J.
Title Thickness dependence of the properties of La0.6Sr0.4MnO3 thin films Type Journal Article
Year 2000 Publication (down) Thin Solid Films Abbreviated Journal
Volume 373 Issue 1-2 Pages 102-106
Keywords
Abstract We have studied the thickness dependence of the transport and magnetic properties of strongly textured La0.6Sr0.4MnO3 thin films grown on MgO and SrTiO3, for thickness between 5 and 500 nm. While the resistivity and the magnetoresistance are strongly affected, the magnetization is only moderately changed. The effect on the metal-insulator transition, the low field magnetoresistance and carrier localization is dependent on the substrate, evidencing the effect of the induced defects and strains. (C) 2000 Elsevier Science S.A. All rights reserved.
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ISSN 0040-6090 ISBN Medium
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Notes ISI:000090045900024 Approved no
Call Number BT @ hernan @ Serial 176
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Author Decca, R.S.; Drew, H.D.; Osquiguil, E.; Maiorov, B.; Guimpel, J.
Title Anomalous proximity effect in underdoped YBa2Cu3O6+x Josephson junctions Type Journal Article
Year 2000 Publication (down) 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.
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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
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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 Maiorov, B.; Nieva, G.; Osquiguil, E.
Title First-order phase transition of the vortex lattice in twinned YBa2Cu3O7 single crystals in tilted magnetic fields Type Journal Article
Year 2000 Publication (down) Physical Review B – Condensed Matter and Materials Physics Abbreviated Journal Phys. Rev. B Condens. Matter Mater. Phys.
Volume 61 Issue 18 Pages 12427-12432
Keywords
Abstract We present an exhaustive analysis of transport measurements performed in twinned YBa2Cu3O7 single crystals which establishes that the vortex solid-liquid transition is first order when the magnetic field H is applied at an angle ? away from the direction of the twin planes. We show that the resistive transitions are hysteretic and the V-I curves are nonlinear, displaying a characteristic S shape at the melting line Hm(T), which scales as ?(?)Hm(T,?), where ?(?) is the anisotropy factor. These features are gradually lost when the critical point H*(?) is approached. Above H*(?) the V-I characteristics show a linear response in the experimentally accessible V-I window, and the transition becomes reversible. Finally we show that the first-order phase transition takes place between a highly correlated vortex liquid in the field direction and a solid state of unknown symmetry. As a consequence, our data support the scenario for a vortex-line melting in twinned YBa2Cu3O7 crystals in contrast to a vortex sublimation as recently suggested for untwinned La2-xSrxCuO4, YBa2Cu3O7 and Bi2Sr2CaCu2O8 [T. Sasagawa et al., Phys. Rev. Lett. 80, 4297 (1998)].
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Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 01631829 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 5; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Maiorov, B.; Centro At Approved no
Call Number BT @ osquigui @ Serial 372
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Author Fainstein, A.; Maiorov, B.; Guimpel, J.; Nieva, G.; Osquiguil, E.
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 (down) 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.
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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 Fasano, Y.; Menghini, M.; de la Cruz, F.; Nieva, G.
Title Weak interaction and matching conditions for replicas of vortex lattices Type Journal Article
Year 2000 Publication (down) 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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Series Volume Series Issue Edition
ISSN 0163-1829 ISBN Medium
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Notes ISI:000165883800075 Approved no
Call Number BT @ hernan @ Serial 219
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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 (down) 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
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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 (down) 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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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 Herbsommer, J.A.; Nieva, G.; Luzuriaga, J.
Title Interaction of vortices with oriented twin boundaries in single-crystal YBa2Cu3O7-delta Type Journal Article
Year 2000 Publication (down) Physical Review B Abbreviated Journal Phys. Rev. B
Volume 61 Issue 17 Pages 11745-11751
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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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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1098-0121 ISBN Medium
Area Expedition Conference
Notes ISI:000086937700090 Approved no
Call Number BT @ hernan @ Serial 228
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Author Niebieskikwiat, D.; Civale, L.; Balseiro, C.A.; Nieva, G.
Title Nonglassy relaxation by double kinks in YBa2Cu3O7-delta with columnar defects Type Journal Article
Year 2000 Publication (down) PHYSICAL REVIEW B Abbreviated Journal
Volume 61 Issue 10 Pages 7135-7141
Keywords
Abstract We present long-term relaxation measurements of the irreversible magnetization in YBa2Cu3O7-delta Single crystals with columnar defects. Within the single vortex pinning regime we find a nonglassy response at intermediate currents, in between the half loops and superkinks glassy regimes. We demonstrate that such behavior is due to double kink excitations whose critical nucleus has a size independent of current, and occur even in the presence of pinning energy dispersion.
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Series Volume Series Issue Edition
ISSN 1098-0121 ISBN Medium
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Notes ISI:000085985800092 Approved no
Call Number BT @ hernan @ Serial 229
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Author Roa Rojas, J.; Jurelo, A.R.; Menegotto Costa, R.; Mendonca Ferreira, L.; Pureur, P.; Orlando, M.T.D.; Prieto, P.; Nieva, G.
Title Fluctuation conductivity and the dynamical universality class of the superconducting transition in the high-Tc cuprates Type Journal Article
Year 2000 Publication (down) Physica C: Superconductivity Abbreviated Journal Physica C
Volume 341-348 Issue 3 Pages 1911-1912
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Abstract Systematic measurements of the fluctuation conductivity in several high-temperature superconducting cuprates show the occurrence of a genuine critical regime. The conductivity exponent is consistent with the predictions of the 3D-XY universality class and yields a dynamical critical exponent z = 1.5.
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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:000165855900185 Approved no
Call Number BT @ hernan @ Serial 223
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