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Author L
Title Dynamic softening of vortex lines in YBa2Cu3O7-? single crystals Type Journal Article
Year 1996 Publication (up) Physica C: Superconductivity and its Applications Abbreviated Journal Phys C Supercond Appl
Volume 260 Issue 3-4 Pages 211-216
Keywords Crystal defects; Magnetic anisotropy; Magnetic couplings; Mathematical models; Single crystals; Transport properties; Vortex flow; Yttrium compounds; Dynamic softening; Flux transformer configuration; Pinning potential; Transport measurements; Vortex correlation; Vortex line; Yttrium barium cuprates; High temperature superconductors
Abstract Transport measurements in the mixed state of oxygen-deficient YBa2Cu3O7-? single crystals using the flux transformer configuration show that the flux liquid changes with increasing anisotropy from strongly correlated to uncorrelated in the field direction. For intermediate coupling, the current inducing loss of vortex correlation has a maximum near the irreversibility temperature. Thus, an effective softening of vortex lines with decreasing temperature is detected. We propose a simple model that accounts for this behavior by including the effects of the pinning potential on the dynamics of vortices.
Address Comn. Nac. de Ener. At
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Notes Cited By (since 1996): 4; Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Righi, E.F.; Comn. Nac. de Ener. At Approved no
Call Number BT @ osquigui @ Serial 384
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Author Martin, J.I.; Wuyts, B.; Maenhoudt, M.; Osquiguil, E.; Vicent, J.L.; Moshchalkov, V.V.; Bruynseraede, Y.
Title Sign reversal of the flux flow Hall effect in oxygen deficient YBa2Cu3Ox films Type Journal Article
Year 1994 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 2 Pages 1451-1452
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Abstract The Hall effect of high temperature superconductors has been reported to slow in some cases a striking sign reversal near Tc, the origin of which is not yet fully understood. We report on measurements of the Hall effect in the mixed state of oxygen deficient YBa2Cu3Ox thin films, for 7?
Address Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Martin, J.I.; Dpto. Fisica de Materiales; Facultad de Ciencias Fisicas; Universidad Complutense 28040 Madrid, Spain Approved no
Call Number BT @ osquigui @ Serial 386
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Author Libbrecht, S.; van Dalen, A.J.J.; Wuyts, B.; Maenhoudt, M.; Gao, Z.X.; Osquiguil, E.; Griessen, R.; Bruynseraede, Y.
Title Magnetic properties of oxygen deficient Yba2Cu3Ox thin films Type Journal Article
Year 1994 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 5 Pages 2889-2890
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Abstract We have invesitgated several superconducting properties of oxygen defiecient YBa2Cu3Ox thin films, with oxygen contents ranging from x = 6.55 to x = 7. By means of torque magnetometry, the temperature dependence of the superconducting current dendity js and relaxation rate of the magnetization Q is measured in an (almost perpendicular) applied magnetic induction of 0.6 T. As the oxygen content is reduced, js decreases, whereas Q increases. Both properties are influenced by the decreased dpoing level as well as the enhanced anisotropy of oxygen depleted YBa2Cu3Ox. Using the Generalixed Inversion Scheme derived by Schnak et al. we obtain the current dependence of the activation energy U(f). We show that U(j) is lowered when the oxygen content is reduced.
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Libbrecht, S.; Laboratorium voor Vaste-Stoffysika en Magnetisme; Katholieke Universiteit B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 387
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Author El Azrak, A.; de Vaulchier, L.A.; Bontemps, N.; Thivet, C.; Guilloux-Viry, M.; Perrin, A.; Wuyts, B.; Osquiguil, E.
Title Optical and transport measurements of YBa2Cu3O6+x thin films (0.38?x?1) Type Journal Article
Year 1994 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 2 Pages 1431-1432
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Abstract We report optical reflectivity and transmission measurements at room temperature on a set of five YBa2Cu3O6+x films for 0.38?x?, and ?{variant}(T) resistivity data down to 10K, prepared from a single YBa2Cu3O7 thin film. In contrast with x=1, as x decreases, the scattering rate deduced from the optical conductivity departs from its linear variation with ?, in correlation with the absence of linearity of ?{variant}(T) versus temperature.
Address Centro Atomico, 8400 S.C. de Bariloche, R.N., Argentina
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: El Azrak, A.; Optique Physique (UPR 5 CNRS); ESPCI; 10 rue Vauquelin 75231 Paris Cedex 05, France Approved no
Call Number BT @ osquigui @ Serial 388
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Author Wuyts, B.; Maenhoudt, M.; Libbrecht, S.; Gao, Z.X.; Osquiguil, E.; Moshchalkov, V.V.; Bruynseraede, Y.
Title Linear relation between the Hall angle slope and the carrier density in YBa2Cu3Ox films Type Journal Article
Year 1994 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 2 Pages 1369-1370
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Abstract A universal relation cot?H??{variant}/RHB = ?T2 + C for the Hall angle ?H has been experimentally observed served in a wide variety of high-Tc systems. In contrast to the linear temperature dependence of the resistivity ?{variant} or the inverse Hall coefficient R-1H, the T2-dependence of cot?H remains valid in under- and overdoped systems. We present a systematic study of cot?H(T) in oxygen deficient epitaxial YBa2Cu3Ox thin films. We find evidence for a linear relation between ?, the slope of cot?H versus T2, and the carrier concentration. Moreover, we find a steep increase in the intercept C = cot?H (T = 0) below x ? 6.6.
Address Laboratorium voor Vaste-Stoffysika en Magnetisme, Katholieke Universiteit Leuven Celestijnenlaan 200D, B-3001 Leuven, Belgium
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Wuyts, B.; Laboratorium voor Vaste-Stoffysika en Magnetisme; Katholieke Universiteit Leuven Celestijnenlaan 200D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 392
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Author van Dalen, A.J.J.; Griessen, R.; Libbrecht, S.; Osquiguil, E.; Bruynseraede, Y.
Title Observation of quantum creep in oxygen deficient YBa2Cu3O7-? at fields up to 7 T Type Journal Article
Year 1994 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 5 Pages 2959-2960
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Abstract Superconducting current densities js and dynamic relaxation rates Q ? d ln js/d ln (dBe/dt) in an oxygen deficient YBa2Cu3O7-? epitaxial film were measured as a function of temperature (1.5K < T < Tirr) in magnetic fields up to 7 T by means of high sensitivity capacitance torquemeters. Below 5 K, the relaxation rate remains high and does not extrapolate to Q = 0 at T = 0K. This is associated to the quantum tunneling of vortices through the energy barrier separating two adjacent vortex configurations. In the case of ohmic dissipation the quantum creep rate is proportional to the normal state resistivity ?{variant}n(0) at T = 0 K. In order to check this theoretical prediction we measured Q as a function of the oxygen content of the sample. The quantum creep rate increases systematically with increasing ?{variant}n(0). However, Q remains finite even when ?{variant}n = 0.
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: van Dalen, A.J.J.; Faculty of Physics and Astronomy; Free University 1081 HV Amsterdam, Netherlands Approved no
Call Number BT @ osquigui @ Serial 393
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Author Libbrecht, S.; Osquiguil, E.; Bruynseraede, Y.
Title Influence of field inhomogeneity on the magnetization of YBCO films Type Journal Article
Year 1994 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 225 Issue 3-4 Pages 337-345
Keywords Magnetization; Superconducting films; SQUID magnetometers; Superconducting ceramics; YBCO superconductors; High temperature superconductors
Abstract DC magnetization data of superconducting thin YBCO films, measured by means of a magnetometer in which the sample is pulled through a set of pick-up coils, are often calculated from pick-up signals which clearly deviate from the ideal response. We show how these signal distortions influence the values obtained for the magnetization, and present a simple model that enables one to simulate the temperature dependence of these distorted pick-up signals, in the case of low-field magnetization measurements. The model is based on the magnetic field inhomogeneity of the magnetometer, in combination with the hysteretic magnetization of the superconducting sample. Optimum values for the model parameters are derived and discussed.
Address Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
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Notes Cited By (since 1996): 11; Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Bruynseraede, Y.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200 D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 394
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Author Wuyts, B.; Osquiguil, E.; Maenhoudt, M.; Libbrecht, S.; Gao, Z.X.; Bruynseraede, Y.
Title Relation between the Hall angle slope and the carrier density in oxygen-depleted YBa2Cu3Ox films Type Journal Article
Year 1994 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 222 Issue 3-4 Pages 341-348
Keywords Doping (additives); Electric conductivity; Hall effect; Mathematical models; Thermal effects; Thin films; Transport properties; Yttrium compounds; Carrier density; Hall angle slope; Oxygen content; Zero temperature intercept; Superconducting films
Abstract A detailed study of the Hall angle cot?H in YBa2Cu3Ox epitaxial thin films with various oxygen contents clearly shows the existence of a linear relation between the slope of cot?H versus T2 and the carrier density. The zero-temperature intercept C=cot?H(T=0 K) and the mobility at room temperature change substantially for an oxygen content x?6.6, indicating that both effects are closely related.
Address Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
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Notes Cited By (since 1996): 8; Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Bruynseraede, Y.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200 D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 395
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Author Libbrecht, S.; Osquiguil, E.; Wuyts, B.; Maenhoudt, M.; Gao, Z.X.; Bruynseraede, Y.
Title Effect of room temperature annealing on the properties of oxygen- deficient YBa2Cu3Ox films Type Journal Article
Year 1993 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 206 Issue 1-2 Pages 51-58
Keywords Annealing; Ceramic materials; Hall effect; Superconducting films; Yttrium compounds; Critical current density; Oxide superconductors; Yttrium barium copper oxides; High temperature superconductors
Abstract Annealing at room temperature of quenched oxygen-depleted YBa2Cu3Oxn (6.5?xn<6.8) films, produces a clear increase in the critical temperature Tc and current density Jc, while the normal state resistivity ?{variant}xx and Hall coefficient RH decrease as a function of annealing time, indicating an increase in carrier density. The enhancement of the critical current density Jc is more pronounced at high fields and temperatures due to a shift of the irreversibility line, which scales with the increasing Tc. The observed changes are accompanied by corresponding changes in the crystalline structure, which can be related to oxygen ordering effects.
Address Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
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Notes Cited By (since 1996): 11; Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Libbrecht, S.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 402
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Author Wuyts, B.; Gao, Z.X.; Libbrecht, S.; Maenhoudt, M.; Osquiguil, E.; Bruynseraede, Y.
Title Growth of particle-free YBa2Cu3O7 films by off-axis sputtering Type Journal Article
Year 1992 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 203 Issue 3-4 Pages 235-239
Keywords Copper oxides; Film growth; Film preparation; Magnetrons; Particles (particulate matter); Sputter deposition; Substrates; Superconductivity; Thin films; Yttrium compounds; Critical current density; Off axis single target magnetron sputtering; Particle free superconducting films; Yttrium barium copper oxides; Superconducting films
Abstract The preparation of good YBa2Cu3O7 thin films is often hindered by the production of non-stoichiometric particles which degrade the superconducting properties of the layer. A systematic study of films prepared by off-axis single target magnetron sputtering shows that the presence of copper-rich particles dramatically decreases the critical current density but does not affect the critical temperature. The formation of these particles can be avoided by carefully adjusting the position of the substrate with respect to the target. Films without off-stoichiometric particles have excellent superconducting properties.
Address Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
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Notes Cited By (since 1996): 10; Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Wuyts, B.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200 D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 403
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