Continuum versus discrete flux behaviour in large mesoscopic Bi(2)Sr(2)CaCu(2)O(8+delta) disks (original) (raw)
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The nucleation of superconductivity in a superconducting disk with a Co/Pt magnetic triangle was studied. We demonstrate that when the applied magnetic field is parallel to the magnetization of the triangle, the giant vortex state of vorticity three splits into three individual Φ0-vortices, due to a pronounced influence of the C3 symmetry of the magnetic triangle. As a result of a strong pinning of the three vortices by the triangle, their configuration remains stable in a broad range of applied magnetic fields. For sufficiently high fields, Φ0-vortices merge and the nucleation occurs through the giant vortex state. The theoretical analysis of this novel reentrant behaviour at the phase boundary, obtained within the Ginzburg -Landau formalism, is in excellent agreement with the experimental data. PACS numbers: 74.78.Na., 75.75.+a, 74.25.Dw
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We have experimentally investigated the magnetisation of a mesoscopic aluminum loop at temperatures well below the superconducting transition temperature T c . The flux quantisation of the superconducting loop was investigated with a µ-Hall magnetometer in magnetic field intensities between ±100Gauss. The magnetic field intensity periodicity observed in the magnetization measurements is expected to take integer values of the superconducting flux quanta Φ 0 = h/2e. A closer inspection of the periodicity, however, reveal a sub flux quantum shift. This fine structure we interpret as a consequence of a so called giant vortex state nucleating towards either the inner or the outer side of the loop. These findings are in agreement with recent theoretical reports.
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