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Heyvaert, I., E. Osquiguil, C. Van Haesendonck, and Y. Bruynseraede. "Etching of screw dislocations in YBa2Cu3O7 films with a scanning tunneling microscope." Applied Physics Letters 61, no. 1 (1992): 111–113.
Abstract: We report on the systematic unrolling of screw dislocations with the scanning tunneling microscope at the surfaces of sputtered, c-axis oriented YBa2Cu3O7 films. The etching is dominated by field induced evaporation and not by mechanical milling of the surface. The process also enables the controlled drawing of nanometer scale grooves on the film surface.
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Neerinck, D., K. Temst, M. Baert, E. Osquiguil, C. Van Haesendonck, Y. Bruynseraede, A. Gilabert, and I. K. Schuller. "Softening of the flux line lattice in Ge/Pb multilayers." Superconductor Science and Technology 5, no. 1S (1992).
Abstract: The authors measured the critical current density Jc of artificially grown Ge/Pb multilayers as a function of the magnetic field H perpendicular to applied perpendicular to the layers. In these layered structures Jc(Hperpendicular to) rapidly drops to a pronounced minimum at a field H*perpendicular to, then increases through a broad maximum and finally decays to zero at H c2 perpendicular to. The systematic evolution of this minimum as a function of temperature, layer thickness and pinning strength allows us to conclude that this peculiar behavior is due to a thermally driven softening of the flux line lattice which can be related either to a magnetic decoupling or a melting of the vortex structure.
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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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Dhalle, M., W. Boon, E. Osquiguil, C. Van Haesendonck, Y. Bruynseraede, J. Kwarciak, and O. Van Der Biest. "Correlation between critical current and resistivity in YBa2Cu3O7." Physica C: Superconductivity and its applications 185-189, no. PART 4 (1991): 2447–2448.
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.
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Neerinck, D., K. Temst, M. Baert, E. Osquiguil, C. Van Haesendonck, Y. Bruynseraede, A. Gilabert, and I. K. Schuller. "Transition in the flux lattice of artificially layered superconductors." Physical Review Letters 67, no. 18 (1991): 2577–2580.
Abstract: We report a novel magnetic-field dependence of the critical-current density Jc in artificially grown Ge/Pb superlattices. In these layered structures Jc exhibits an unexpected minimum as a function of perpendicular applied field, unlike any ever observed in other superconductor systems. The systematic evolution of this minimum as a function of layer thicknesses, temperature and pinning strength is related to either flux-lattice decoupling or melting.
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Neerinck, D., K. Temst, M. Baert, E. Osquiguil, C. Van Haesendonck, Y. Bruynseraede, A. Gilabert, and I. K. Schuller. "Thermally induced transition in the vortex lattice of Ge/Pb multilayers." Physica C: Superconductivity and its applications 185-189, no. PART 3 (1991): 2061–2062.
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.
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