Libbrecht, S., E. Osquiguil, B. Wuyts, M. Maenhoudt, Z. X. Gao, and Y. Bruynseraede. "Effect of room temperature annealing on the properties of oxygen- deficient YBa2Cu3Ox films." Physica C: Superconductivity and its applications 206, no. 1-2 (1993): 51–58.
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.
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Wuyts, B., Z. X. Gao, S. Libbrecht, M. Maenhoudt, E. Osquiguil, and Y. Bruynseraede. "Growth of particle-free YBa2Cu3O7 films by off-axis sputtering." Physica C: Superconductivity and its applications 203, no. 3-4 (1992): 235–239.
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.
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Nieva, G., E. Osquiguil, J. Guimpel, M. Maenhoudt, B. Wuyts, Y. Bruynseraede, M. B. Maple, and I. K. Schuller. "Photoinduced enhancement of superconductivity." Applied Physics Letters 60, no. 17 (1992): 2159–2161.
Abstract: We show clear and conclusive experimental evidence for the enhancement of superconductivity in GdBa2Cu3Ox and YBa 2Cu3Ox thin films by photoexcitation. Upon laser illumination the critical temperature increases while the resistivity of the material decreases. The relaxation back to the original state is very slow, of the order of days at room temperature. The existence of this effect opens the possibility of fabricating weak-link devices with in situ tunable superconducting characteristics.
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Osquiguil, E., M. Maenhoudt, B. Wuyts, and Y. Bruynseraede. "Controlled preparation of oxygen deficient YBa2Cu 3Ox films." Applied Physics Letters 60, no. 13 (1992): 1627–1629.
Abstract: We describe a simple method based on the oxygen pressure-temperature phase diagram to prepare oxygen deficient YBa2Cu3Ox thin films. Systematic critical temperature and x-ray diffraction experiments clearly show that films with different oxygen contents (6.6?x?7) are obtained in a controlled, reproducible, and reversible way.
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Nieva, G., E. Osquiguil, J. Guimpel, M. Maenhoudt, B. Wuyts, Y. Bruynseraede, M. B. Maple, and I. K. Schuller. "Photoinduced changes in the transport properties of oxygen-deficient YBa2Cu3Ox." Physical Review B 46, no. 21 (1992): 14249–14252.
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.
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Vanacken, J., S. Libbrecht, M. Maenhoudt, C. Van Haesendonck, E. Osquiguil, and Y. Bruynseraede. "The magnetic moment relaxation in oxygen-deficient YBa2Cu3Ox." Physica C: Superconductivity and its applications 197, no. 1-2 (1992): 9–14.
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.
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Bruynseraede, Y., E. Osquiguil, M. Maenhoudt, B. Wuyts, G. Nieva, J. Guimpel, D. Lederman, and I. K. Schuller. "New Properties of Oxygen Depleted YBa2Cu3Ox Films." Proceedings of the II International Conference on Macroscopic Quantum Phenomena ICMQP-2 (1992): 253.
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