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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 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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ISSN 09214534 (ISSN) ISBN Medium
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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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Author Vanacken, J.; Libbrecht, S.; Maenhoudt, M.; Van Haesendonck, C.; Osquiguil, E.; Bruynseraede, Y.
Title The magnetic moment relaxation in oxygen-deficient YBa2Cu3Ox Type Journal Article
Year 1992 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 197 Issue 1-2 Pages 9-14
Keywords Magnetic Measurements – Relaxation; Oxygen – Concentration; Relaxation Processes – High Temperature Effects; Relaxation Processes – Magnetic Field Effects; Magnetic Moment Relaxation; Oxygen Deficiency; Yttrium Barium Copper Oxides; High Temperature Superconductors
Abstract The magnetic moment relaxation in polycrystalline YBa2Cu3Oxmaterial has been studied using zero-field-cooled measurements. The temperature dependence of the relaxation rate shows a field-dependent maximum. When the oxygen content is reduced, the maximum shifts towards lower temperatures. This shift is directly related to a decrease of the intragrain critical current density in the oxygen-deficient material, inducing a decrease of the field H* for complete flux penetration. The characteristic activation energies for depinning in the oxygen-deficient material are below 20 meV.
Address Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, 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: Vanacken, J.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200 D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 409
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Author Dhalle, M.; Boon, W.; Osquiguil, E.; Van Haesendonck, C.; Bruynseraede, Y.; Kwarciak, J.; Van Der Biest, O.
Title Correlation between critical current and resistivity in YBa2Cu3O7 Type Journal Article
Year 1991 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 185-189 Issue PART 4 Pages 2447-2448
Keywords Ceramic Materials; Yttrium Compounds--Electric Conductivity; Critical Currents; Oxide Superconductors; Yttrium Barium Copper Oxides; High Temperature Superconductors
Abstract Critical current versus temperature measurements were carried out in ceramic YBa2Cu3O7 samples. The samples were all prepared using the same sintering procedure, but starting from powders obtained by different wet and dry methods. All samples showed a linear Jc vs. T behaviour, typical of Josephson weak-link coupling, with a slope that depends on the preparation method. Using the Ambegaokar-Baratoff relation for Jc, the difference in slopes can be attributed to a change in the characteristic value of the junction resistance. This value turns out to be clearly correlated with the resistivity in the normal state.
Address Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, de Croylaan 2, 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: Dhalle, M.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 410
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Author Neerinck, D.; Temst, K.; Baert, M.; Osquiguil, E.; Van Haesendonck, C.; Bruynseraede, Y.; Gilabert, A.; Schuller, I.K.
Title Thermally induced transition in the vortex lattice of Ge/Pb multilayers Type Journal Article
Year 1991 Publication (up) Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 185-189 Issue PART 3 Pages 2061-2062
Keywords Germanium And Alloys; Lead And Alloys; Superconducting Films; Thermal Effects; Critical Currents; Multilayers; Metallic Films
Abstract We report on a novel magnetic field dependence of the critical current density of M.B.E. grown Ge/Pb insulator/superconductor multilayers. When the magnetic field is applied perpendicular to the layers, the critical current density Jc drops to a minimum, followed by a broad maximum before finally decaying monotonously to zezero with increasing magnetic field. The dependence of this effect on pinning strength, temperature, and layer thickness suggests either a thermally driven coupling/decoupling transition, or melting of the vortex lattice.
Address Physics Department, University of California, San Diego, CA 92093-0319, United States
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Neerinck, D.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; K.U. Leuven B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 412
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