| Records |
| Author |
Van Dalen, A.J.J.; Griessen, R.; Libbrecht, S.; Bruynseraede, Y.; Osquiguil, E. |
| Title |
Quantum creep and pinning properties of oxygen-deficient YBa2Cu3Oxn films |
Type |
Journal Article |
| Year |
1996 |
Publication |
Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B Condens. Matter Mater. Phys. |
| Volume |
54 |
Issue |
2 |
Pages |
1366-1381 |
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| Abstract |
A high sensitivity capacitance torquemeter has been used for a comprehensive investigation of the induced current densities and dynamic relaxation rates in a YBa2Cu3Oxn film with nominal oxygen content varying between xn=6.55 and xn=7.0. The dynamic relaxation rate Q does not extrapolate to zero at T=0 K, indicating the presence of quantum creep. By changing the oxygen content of the film it is possible to investigate the relation between the quantum creep rate Q(0) and the normal-state resistivity pn(0) at low temperature. Although Q(0) increases monotonically with pn, it is found that Q(0) is not proportional to pn(0), in contrast to the predictions of a theory based on dissipative tunneling of collectively pinned single vortices [Blatter et al., Rev. Mod. Phys. 66, 1125 (1994)]. The experimental results imply that in YBa2Cu3O7 quantum creep takes place in a transition regime between Hall tunneling and dissipative tunneling. For lower oxygen contents the quantum creep regime moves towards the dissipative limit. For each oxygen content the characteristic pinning energy Uc(0) at T=0 is obtained by a linear extrapolation to T= 0 K of the T/Q versus T curves. The critical current density jc at T=0 is determined independently by a linear extrapolation of the measured Injs versus T curves. A power-law relation Uc(0)?[jc(0)]p with p? 0.5 is found, indicating single vortex pinning at higher temperatures. This is confirmed by a detailed analysis of the measured current densities and relaxation rates by means of the generalized inversion scheme developed by Schnack et al. [Phys. Rev. B 48, 13 178 (1993)]. For xn? 6.6 at Be= 0.6 T and for xn? 6.7 at Be= 2.0 T the calculated temperature dependence of jc and Uc agrees remarkably well with a model based on three-dimensional single vortex pinning caused by spatial fluctuations in the charge carrier mean free path. At lower oxygen contents and higher magnetic-fields the agreement gradually breaks down due to the increasing importance of thermal fluctuations. |
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Montell Polyolefins, Centre Ricerche G. Natta, P. Le P. to G. Donegani 12, 44100 Ferrara, Italy |
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01631829 (ISSN) |
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Cited By (since 1996): 27; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Van Dalen, A.J.J.; Materials Science Division; Argonne National Laboratory Argonne, IL 60439, United States; References: Mota, A.C., Pollini, A., Visani, P., M |
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BT @ osquigui @ |
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383 |
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Osquiguil, E.; Maenhoudt, M.; Wuyts, B.; Bruynseraede, Y.; Lederman, D.; Schuller, I.K. |
| Title |
Photoexcitation and oxygen ordering in YBa2Cu3Ox films |
Type |
Journal Article |
| Year |
1994 |
Publication |
Physical Review B |
Abbreviated Journal |
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| Volume |
49 |
Issue |
5 |
Pages |
3675-3678 |
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| 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. |
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Physics Department-0319, University of California-San Diego, San Diego, CA 92093-0319, United States |
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01631829 (ISSN) |
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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 |
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BT @ osquigui @ |
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385 |
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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 |
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? |
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Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium |
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09214534 (ISSN) |
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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 |
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BT @ osquigui @ |
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386 |
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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 |
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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09214534 (ISSN) |
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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 |
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BT @ osquigui @ |
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387 |
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Griessen, R.; Wen Hai-Hu; Van Dalen, A.J.J.; Dam, B.; Rector, J.; Schnack, H.G.; Libbrecht, S.; Osquiguil, E.; Bruynseraede, Y. |
| Title |
Evidence for mean free path fluctuation induced pinning in YBa2Cu3O7 and YBa2Cu4O8 films |
Type |
Journal Article |
| Year |
1994 |
Publication |
Physical Review Letters |
Abbreviated Journal |
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| Volume |
72 |
Issue |
12 |
Pages |
1910-1913 |
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| Abstract |
The critical current jc and the pinning energy Uc have been determined for three types of yttrium-based superconducting films from current js and dynamic relaxation Q=d lnjs/d ln(dB/dt) data by means of the generalized inversion scheme. For B<2 T and T<80 K the temperature dependence of jc and Uc for all films is found to be in excellent agreement with a model of single vortices pinned by randomly distributed weak pinning centers via spatial fluctuations of the charge carrier mean free path. Pinning due to spatial fluctuations of Tc is not observed. |
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Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, 4001-Leuven, Belgium |
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00319007 (ISSN) |
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Cited By (since 1996): 103; Export Date: 17 April 2009; Source: Scopus; doi: 10.1103/PhysRevLett.72.1910; Language of Original Document: English; Correspondence Address: Griessen, R.; Faculty of Physics and Astronomy; Free University 1081 HV Amsterdam, Netherlands |
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BT @ osquigui @ |
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389 |
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Lederman, D.; Hasen, J.; Schuller, I.K.; Osquiguil, E.; Bruynseraede, Y. |
| Title |
Photoinduced superconductivity and structural changes in high temperature superconducting films |
Type |
Journal Article |
| Year |
1994 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
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| Volume |
64 |
Issue |
5 |
Pages |
652-654 |
| Keywords |
Annealing; Electric conductivity measurement; Lighting; Oxygen; Praseodymium compounds; Quenching; Semiconducting films; Structure (composition); Superconductivity; Thermal effects; Thin films; Yttrium compounds; Contraction; Oxygen vacancy; Photoinduced superconductivity; Stoichiometry; Superconducting critical temperature; High temperature superconductors |
| Abstract |
The illumination of PryGd1-yBa2Cu 3Ox semiconducting and superconducting thin films increases their critical temperatures and decreases their normal state resistivities if and only if the films are oxygen deficient. Moreover, these changes are enhanced near the Pr-induced metal-insulator transition. Light also causes a contraction of the c-axis in YBa2Cu3Ox which is correlated with the observed photoinduced resistivity changes. These changes are similar to those observed when oxygen-deficient YBa 2Cu3Ox is enriched with oxygen or annealed at room temperature after quenching from high temperatures. |
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Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium |
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00036951 (ISSN) |
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Cited By (since 1996): 37; Export Date: 17 April 2009; Source: Scopus; doi: 10.1063/1.111078; Language of Original Document: English; Correspondence Address: Lederman, D.; Physics Department; University of California-San Diego San Diego, CA 92093-0319, United States |
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BT @ osquigui @ |
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390 |
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Gao, Z.X.; Heyvaert, I.; Wuyts, B.; Osquiguil, E.; Haesendonck, C.V.; Bruynseraede, Y. |
| Title |
Evidence for a “brick wall” microstructure in epitaxial YBa 2Cu3Ox films |
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Journal Article |
| Year |
1994 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
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| Volume |
65 |
Issue |
6 |
Pages |
770-772 |
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We have measured the in-plane (ab plane) critical current density J c in sputtered, c-axis oriented YBa2Cu3O x films as a function of the oxygen content x. The important reduction of Jc with decreasing x can be explained in terms of a “brick wall” microstructure, where the critical current density is dominated by the coupling strength (along the c axis) between the superconducting CuO 2 planes. Scanning tunneling microscopy images of the film surfaces are consistent with the presence of the brick wall structure, which apparently results from the overlap between terraces belonging to adjacent spiral-shaped islands. |
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Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium |
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00036951 (ISSN) |
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Export Date: 17 April 2009; Source: Scopus; doi: 10.1063/1.112225; Language of Original Document: English; Correspondence Address: Gao, Z.X.; Laboratorium voor Vaste-Stoffysica en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200D B-3001 Leuven, Belgium |
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no |
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BT @ osquigui @ |
Serial |
391 |
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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 |
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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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. |
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Laboratorium voor Vaste-Stoffysika en Magnetisme, Katholieke Universiteit Leuven Celestijnenlaan 200D, B-3001 Leuven, Belgium |
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09214534 (ISSN) |
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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 |
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BT @ osquigui @ |
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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 |
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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09214534 (ISSN) |
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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 |
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393 |
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Libbrecht, S.; Osquiguil, E.; Bruynseraede, Y. |
| Title |
Influence of field inhomogeneity on the magnetization of YBCO films |
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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. |
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Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium |
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09214534 (ISSN) |
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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 |
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394 |
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