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Author Libbrecht, S.; Osquiguil, E.; Bruynseraede, Y.
Title (up) Influence of field inhomogeneity on the magnetization of YBCO films Type Journal Article
Year 1994 Publication 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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ISSN 09214534 (ISSN) ISBN Medium
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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 (up) Influence of the oxygen content on the normal-state Hall angle in YBa2Cu3Oxn films Type Journal Article
Year 1993 Publication Physical Review B Abbreviated Journal
Volume 47 Issue 9 Pages 5512-5515
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Abstract We report on measurements of in-plane resistivity ?ab(T) and Hall coefficient RH(T) in c-axis-oriented oxygen-deficient YBa2Cu3Oxn thin films. Independent of the changes induced in RH(T) and ?ab(T) by the oxygen depletion, a quadratic temperature dependence is observed for the Hall angle ?H. The slope of cot?H versus T2 decreases as the oxygen content xn is reduced and saturates in the Tc(xn)=60 K plateau region. The results are discussed in the framework of the two-dimensional Luttinger liquid theory as proposed by Anderson.
Address Laboratorium Voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
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ISSN 01631829 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 27; Export Date: 17 April 2009; Source: Scopus; doi: 10.1103/PhysRevB.47.5512; Language of Original Document: English; Correspondence Address: Wuyts, B.; Laboratorium Voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 398
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Author Vanacken, J.; Osquiguil, E.; Bruynseraede, Y.
Title (up) Irreversibility line and critical currents in oxygen deficient YBa2Cu3Ox ceramics Type Journal Article
Year 1991 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 183 Issue 1-3 Pages 163-166
Keywords Ceramic Materials; Crystals; Oxygen; Yttrium Compounds; Critical Currents; Oxide Superconductors; Yttrium Barium Copper Oxides; High Temperature Superconductors
Abstract The influence of oxygen concentration on the irreversibility line and critical current of polycrystalline YBa2Cu3Ox was determined using field and zero-field cooled magnetic measurements and magnetic hysteresis data. Although the field dependence of Tirr(H) is unchanged, the irreversibility line shifts to lower temperatures for decreasing oxygen content and the critical current density is strongly reduced.
Address Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
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ISSN 09214534 (ISSN) ISBN Medium
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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: Vanacken, J.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200D 3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 413
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Author Wuyts, B.; Maenhoudt, M.; Libbrecht, S.; Gao, Z.X.; Osquiguil, E.; Moshchalkov, V.V.; Bruynseraede, Y.
Title (up) Linear relation between the Hall angle slope and the carrier density in YBa2Cu3Ox films Type Journal Article
Year 1994 Publication 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 Libbrecht, S.; van Dalen, A.J.J.; Wuyts, B.; Maenhoudt, M.; Gao, Z.X.; Osquiguil, E.; Griessen, R.; Bruynseraede, Y.
Title (up) Magnetic properties of oxygen deficient Yba2Cu3Ox thin films Type Journal Article
Year 1994 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 5 Pages 2889-2890
Keywords
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 van Dalen, A.J.J.; Griessen, R.; Libbrecht, S.; Osquiguil, E.; Bruynseraede, Y.
Title (up) Observation of quantum creep in oxygen deficient YBa2Cu3O7-? at fields up to 7 T Type Journal Article
Year 1994 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 5 Pages 2959-2960
Keywords
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 Osquiguil, E.; Maenhoudt, M.; Wuyts, B.; Bruynseraede, Y.; Lederman, D.; Schuller, I.K.
Title (up) Photoexcitation and oxygen ordering in YBa2Cu3Ox films Type Journal Article
Year 1994 Publication Physical Review B Abbreviated Journal
Volume 49 Issue 5 Pages 3675-3678
Keywords
Abstract We report on the photoinduced enhancement of the critical temperature ?Tc and the in-plane conductivity ??ab measured in a c-axis-oriented YBa2Cu3Ox film as a function of oxygen concentration (6.4?x?7). Both ?Tc and ??ab decrease with the oxygen content, display a plateaulike behavior for 6.6?x?6.75, and become zero at x=7. This dependence of ?Tc on x is similar to that observed for the Tc enhancement due to ordering effects in oxygen-deficient YBa2Cu3Ox single crystals. We propose that the persistent photoinduced changes in YBa2Cu3Ox films are due to photoassisted oxygen ordering.
Address Physics Department-0319, University of California-San Diego, San Diego, CA 92093-0319, United States
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ISSN 01631829 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 86; Export Date: 17 April 2009; Source: Scopus; doi: 10.1103/PhysRevB.49.3675; Language of Original Document: English; Correspondence Address: Osquiguil, E.; Laboratorium Voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200 D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 385
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Author Osquiguil, E.; Maenhoudt, M.; Wuyts, B.; Bruynseraede, Y.; Lederman, D.; Nieva, G.; Guimpel, J.; Schuller, I.K.
Title (up) Photoexcitation effects in YBa2Cu3Ox Type Journal Article
Year 1993 Publication Journal of Alloys and Compounds Abbreviated Journal J Alloys Compd
Volume 195 Issue C Pages 667-670
Keywords Barium compounds; Ceramic materials; Copper oxides; High temperature superconductors; Oxides; Photoelectricity; Yttrium compounds; C-axis oriented films; Photoexcitation effects; Photoinduced phenomena; Yttrium barium cuprates; Superconducting films
Abstract We show through photoexcitation experiments carried out on YBa2Cu3Ox c-axis oriented films that photoinduced phenomena are not restricted to insulating samples. Superconducting films with critical temperatures varying between 2 K and 40 K show a clear enhancement of the superconducting transition after illumination. The increase in Tc is accompanied by a corresponding decrease in the resistivity ?, and an increase in the Hall coefficient RH, indicative of an increased carrier density. Furthermore, the carrier mobility is also affected by illumination.
Address Physics Department – 0319, University of California – San Diego, La Jolla, CA 92093-0319, United States
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ISSN 09258388 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 4; Export Date: 17 April 2009; Source: Scopus; CODEN: JALCE; Language of Original Document: English; Correspondence Address: Osquiguil, E.; Laboratorium voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 401
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Author Nieva, G.; Osquiguil, E.; Guimpel, J.; Maenhoudt, M.; Wuyts, B.; Bruynseraede, Y.; Maple, M.B.; Schuller, I.K.
Title (up) Photoinduced changes in the transport properties of oxygen-deficient YBa2Cu3Ox Type Journal Article
Year 1992 Publication Physical Review B Abbreviated Journal
Volume 46 Issue 21 Pages 14249-14252
Keywords
Abstract We show that illumination of oxygen-deficient metallic YBa2Cu3Ox films produces a change in the Hall coefficient, an increase in the critical temperature, and a decrease in the electrical resistivity. These changes relax to equilibrium with characteristic times of the order of days, and are due to variations in both the carrier density and mobility. The relaxation times are of the same order of magnitude as the ones measured in nonilluminated oxygen-deficient films immediately after quenching.
Address Laboratory for Solid State Physics and Magnetism, University of Leuven, B3001 Leuven, Belgium
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Notes Cited By (since 1996): 62; Export Date: 17 April 2009; Source: Scopus; doi: 10.1103/PhysRevB.46.14249; Language of Original Document: English; Correspondence Address: Nieva, G.; Physics Department; University of California(enSan Diego San Diego, CA 92093-0319, United States Approved no
Call Number BT @ osquigui @ Serial 407
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Author Lederman, D.; Osquiguil, E.; Nieva, G.; Guimpel, J.; Hasen, J.; Bruynseraede, Y.; Schuller, I.K.
Title (up) Photoinduced enhancement of superconductivity Type Journal Article
Year 1994 Publication Journal of Superconductivity Abbreviated Journal J Supercond
Volume 7 Issue 1 Pages 127-130
Keywords photoconduction; Superconductivity; thin films; Copper oxides; Hall effect; Order disorder transitions; Radiation effects; Superconductivity; X ray analysis; Josephson coupling; Oxide superconductors; Yttrium barium cuprates; High temperature superconductors
Abstract The photoinduced enhancement of superconductivity in RBa2Cu3Ox (R=rare earth or yttrium) and PryR1-yBa2Cu3Ox was explored through temperature-dependent resistivity, Hall coefficient and mobility, and x-ray diffraction measurements. The increases in Tc are enhanced near the metal-insulator transition, although photoinduced changes always exist in oxygendeficient samples. Several explanations, including intergrain Josephson coupling, photoassisted oxygen ordering, and the trapping of photogenerated electrons in oxygen vacancies, are discussed.
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Publisher Kluwer Academic Publishers-Plenum Publishers Place of Publication Editor
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ISSN 08961107 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 2; Export Date: 17 April 2009; Source: Scopus; CODEN: JOUSE; doi: 10.1007/BF00730382; Language of Original Document: English; Correspondence Address: Lederman, D.; Physics Department; University of California; San Diego La Jolla, 92093-0319, California, United States Approved no
Call Number BT @ osquigui @ Serial 397
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