| 1. |
- Andersson, Magnus, et al.
(författare)
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H-T PHASE-DIAGRAM OF DYBA2CU3O7-DELTA(Y0.45PR0.55)BA2CU3O7-DELTA MULTILAYERS IN THE MIXED-STATE
- 1994
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Ingår i: Physica. C, Superconductivity. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 235, s. 2617-2618
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Tidskriftsartikel (refereegranskat)abstract
- From measurements of I-V characteristics of DyBa2Cu3O7-delta/(Y0.45Pr0.55)Ba2Cu3O7.delta multilayers, we have experimentally determined the characteristic temperature separating the vortex liquid from the vortex solid. We suggest that the cross-over temperature is determined by the anisotropy given by the artificially layered structure of these multilayers and that the studied system can be used as a test system for vortex dynamics.
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| 2. |
- Andersson, Magnus, et al.
(författare)
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Vortex solid-to-liquid transition in DyBa2Cu3O7-delta/(Y0.45Pr0.55)Ba2Cu3O7-delta multilayers
- 1996
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 54:1, s. 675-681
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Tidskriftsartikel (refereegranskat)abstract
- Current-voltage (I-V) characteristics of a coupled multilayer system consisting of thin (24 Angstrom) superconducting layers of DyBa2Cu3O7-delta each separated by 96 Angstrom of (Y0.45Pr0.55)Ba2Cu3O7-delta have been studied in the mixed state. Analyses of vortex glass scaling and signs of the clean system melting transition in the dynamics of our multilayers both suggest that the vortex system is close to three-dimensional for magnetic fields up to several T. Therefore, the theoretically predicted crossover when in-plane vortex correlations become more important than out-of-plane vortex correlations (occurring at a few tenths of a T in our multilayers) does not correspond to a complete decoupling of the superconducting layers in these materials.
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| 3. |
- Fabrega, Lourdes, et al.
(författare)
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Vortex dynamics and vortex phase diagram in artificial oxide superlattices
- 1996
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 222:4, s. 379-384
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Tidskriftsartikel (refereegranskat)abstract
- DyBa2Cu3O7/(Y1-xPrx)Ba2Cu3O7 multilayers are model materials to study the nature of the vortex system in high-temperature superconductors and its dynamics. Indeed, by changing in such structures the thickness of the superconducting and the alloy layers, and the composition of the alloy, we can control at wish the critical temperature, the anisotropy and the pinning strength. Additionally, finite thickness effects may be studied. We review here our results on the study of the flux motion and phase diagram in coupled multilayers, displaying an intermediate anisotropy between those of YBa2Cu3 O-7 and Bi2Sr2CaCu2O8. Transport measurements with an applied field H/c allow to identify the solid and liquid phases in the mixed state, and reveal the presence of a field-induced crossover in the thermally activated dynamics of both phases, which lead us to draw a possible mixed state phase diagram for these artificial superconductors and correlate it to the existing results for other HTS.
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| 4. |
- Fischer, Oystein, et al.
(författare)
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Investigation of coupled DyBa2Cu3O7-(Y1-xPrx)Ba2Cu3O7 multilayer structures
- 1994
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Ingår i: Superconducting Superlattices and Multilayers. - Bellingham : SPIE - International Society for Optical Engineering. - 0819414522 ; , s. 134-141
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Konferensbidrag (refereegranskat)abstract
- We report on the behavior of high Tc superconductor coupled multilayer structures in magnetic field perpendicular to the ab plane. In these structures the number N of superconducting layers in the sample has been systematically varied. We extract the activation energy for flux motion from resistive measurements of the superconducting transitions. For samples containing N 24 angstroms thick DyBa2Cu3O7 layers, each separated from the next by 96 angstroms of an (Y0.45Pr0.55)Ba2Cu3O7 alloy, we find that the activation energy U increases linearly with the number N of layers for N < 3 - 4, and then saturates. The linear increase of U is taken as an evidence that coupling through (Y0.45Pr0.55)Ba2Cu3O7 increases the correlated volume involved in the flux motion and thus U. For N = 3 stacked pancake vortices move rigidly and the vortex lattice is 2D. For N > 3 - 4 shear of the vortex lattice becomes important, the vortex lattice dimensionally crosses-over to 3D, and the activation energy saturates.
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| 5. |
- Fivat, Patrice, et al.
(författare)
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Parallel and perpendicular field investigations of coupled high-Tc multilayer structures
- 1994
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Ingår i: Superconducting Superlattices and Multilayers. - Bellingham : SPIE - International Society for Optical Engineering. ; , s. 192-198
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Konferensbidrag (refereegranskat)abstract
- We report on the behavior of high Tc superconductors coupled multilayer structures in magnetic field parallel and perpendicular to the ab plane. These structures consist of N 24 angstroms thick DyBa2Cu3O7 layers, each separated from the next by 96 angstroms of an (Y0.45Pr0.55)Ba2Cu3O7 alloy. This alloy allows a coupling of the superconducting layers as demonstrated by measurements of the activation energies for flux motion U. For a N = 15 sample one finds, in perpendicular fields, that a correlated motion of pancake vortices occurs with a characteristic length of about 480 angstroms. Additionally, U is found to be proportional to logB at low fields while at higher fields a power law behavior is observed. In parallel field we find U to be field independent up to 1 T, suggesting that the vortices are trapped at low fields in the material where weak superconductivity is induced by proximity effect.
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| 6. |
- Obara, Haruhiko, et al.
(författare)
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Critical current properties of DyBa2Cu3O7/(Y1−xPrx)Ba2Cu3O7 multilayers
- 1994
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Ingår i: Physica. C, Superconductivity. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 235-240:PART 5, s. 2997-2998
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Tidskriftsartikel (refereegranskat)abstract
- Transport critical currents of DyBa2Cu3O7/(Y1−xPrx)Ba2Cu3O7 (DyBCO/YPrBCO) multilayers have been measured. Using careful meausurements of the temperature and magnetic field dependence of critical current density Jc of the multilayers, we observed two distinct regions in the solid vortex state. From these experimental results, we discuss the dimensionality, the vortex states, and the vortex pinning in the multilayers.
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| 7. |
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| 8. |
- Obara, Haruhiko, et al.
(författare)
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Vortex system in coupled DyBa2Cu3O7-delta(Y0.45Pr0.55)Ba2Cu3O7-delta heterostructures
- 1996
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Ingår i: Czechoslovak Journal of Physics. - 0011-4626 .- 1572-9486. ; 46:SUPPL. 3, s. 1565-1566
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Tidskriftsartikel (refereegranskat)abstract
- Transport measurements have been used to determine the vortex phase diagram (H parallel to c) of coupled heterostructures made of superconducting ultra-thin DyBa2Cu3O7-delta layers separated by semiconducting (Y0.45Pr0.55)Ba2Cu3O7-delta layers. These structures have an intermediate anisotropy between those of YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+d. The solid-to-liquid transition and the flux dynamics have been investigated as a function of the total sample thickness d. Analyses of the parameters describing the thermally activated dissipation in the solid and liquid phases reveal a field induced crossover characterized by two fields, H-on(T) and H*>H-on. We discuss the meaning of these features and their relationship with results in bulk high temperature superconductors.
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| 9. |
- Triscone, Jean-Marc, et al.
(författare)
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2-DIMENSIONAL AND 3-DIMENSIONAL VORTEX LATTICE-DYNAMICS IN DYBA2CU3O7-(Y1-XPRX)BA2CU3O7 COUPLED HETEROSTRUCTURES
- 1994
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 50:2, s. 1229-1236
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Tidskriftsartikel (refereegranskat)abstract
- Vortex dynamics is studied in coupled multilayer structures, containing N 24-angstrom-thick DyBa2Cu3O7 layers, each separated from the next by 96 angstrom of (Y1-xPrx)Ba2Cu3O7 (x = 0. 4, 0.55). When the magnetic field is parallel to the c axis, we find that the activation energy U for flux motion increases linearly with the number of superconducting layers N in the structure for N < 3. This linear increase is the result of the coupled motion of pancake vortices belonging to different DyBa2Cu3O7 layers. For larger N samples the activation energy saturates meaning that the vortex lattice is turning three dimensional. In contrast to samples whose vortex lattice is purely two dimensional and for which we find the activation energy for flux motion proportional to log10B, samples in these series show a crossover to a power-law behavior, U almost-equal-to B-0.5, at a magnetic field H* which decreases as N increases.
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