Haberkorn, N., G. Bridoux, E. Osquiguil, G. Nieva, and J. Guimpel. "Hall effect in a GdBa2Cu3O7-?/La0.75 Sr0.25MnO3 perovskite bilayer." Applied Surface Science 254, no. 1 SPEC. ISS. (2007): 222–224.
Abstract: We present results on the Hall coefficient RH in the normal state for a GdBa2Cu3O7-?/La0.75 Sr0.25MnO3 bilayer and a La0.75Sr0.25MnO3 film grown by dc magnetron sputtering on (1 0 0) SrTiO3. We find that the electric transport on the bilayer can be qualitatively described using a simple parallel layers model. The GdBa2Cu3O7-? layer presents a carrier density approximately equal to that reported for 7 – ? = 6.85 oxygen doping. Also we observe an unexpected presence of two Hall resistivity regimes, effects that may be associated with the internal magnetic field induced on the superconducting layer by the ferromagnetic layer.
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Lederman, D., J. Hasen, I. K. Schuller, E. Osquiguil, and Y. Bruynseraede. "Photoinduced superconductivity and structural changes in high temperature superconducting films." Applied Physics Letters 64, no. 5 (1994): 652–654.
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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Osquiguil, E., R. Decca, G. Nieva, L. Civale, and F. de la Cruz. "La1.80 Sr0.20 CuO4-delta a clean limit superconductor." Solid State Communications 65, no. 6 (1988): 491–494.
Abstract: The electrical resistivity of the superconductor La1.80Sr0.20Cu04-? has been measured in a wide range of temperatures as a function of oxygen and vacuum heat treatments. The resistivity changes reversibly orders of magnitude with oxygen concentration. There is no sign of saturation at high temperatures, even for samples where the resistivity is increased by heat treatment in vacuum. Using the experimental data and general arguments it is concluded that the ceramic superconductors are high ? materials in the clean limit.
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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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Vanacken, J., E. Osquiguil, and Y. Bruynseraede. "Irreversibility line and critical currents in oxygen deficient YBa2Cu3Ox ceramics." Physica C: Superconductivity and its applications 183, no. 1-3 (1991): 163–166.
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.
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Watt. "Photoinduced changes in Raman spectra of YBa2Cu3O6.4 films." Journal of Superconductivity 7, no. 1 (1994): 131–136.
Abstract: The evolution of Raman spectra with illumination has been studied in YBa2Cu3O6.4 films at temperatures between 5-300 K. Low laser power has always been used to avoid local overheating, which was controlled by measuring the local temperature by the Stokes/anti-Stokes ratio. Three important photoinduced effects have been found: (i) the enhancement of the intensity of the observed phonon modes: (Cu(2) at 141 cm-1, O(2)-O(3) at 338 cm-1, and O(4) at 488 cm-1), which may be related to the ordering of oxygen vacancies, (ii) the increase of the electronic scattering background for low Raman frequencies ?, which is in agreement with the enhancement of the static conductivity ?(??0) after illumination, and (iii) the suppression of the intensity of the two-magnon band, which may be caused by the increase of charge carriers due to photodoping.
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Wuyts, B., E. Osquiguil, M. Maenhoudt, S. Libbrecht, Z. X. Gao, and Y. Bruynseraede. "Relation between the Hall angle slope and the carrier density in oxygen-depleted YBa2Cu3Ox films." Physica C: Superconductivity and its applications 222, no. 3-4 (1994): 341–348.
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.
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