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Influence of microscopic defects in type-II superconducting thin films on the magnetic flux penetration

Johannes Eisenmenger, Paul Leiderer, Michael Wallenhorst, Horst Dötsch

DOI 10.1103/PhysRevB.64.104503 · Physical Review B

T1

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Abstract

The magnetic flux penetration into thin type-II superconducting films with circular defects is investigated. The artificial circular defects (diameter =40 μm) in an YBa2Cu3O7−δ thin film (thickness ≈300 nm) were prepared by pulse-laser irradiation. The flux penetration into the zero-field-cooled superconducting film was visualized by means of the magneto-optic method. A stepwise increase of the external magnetic field allowed a detailed investigation of the influence of local defects on the flux penetration. For a magnetic field parallel to a long sample (longitudinal geometry) with a long cylindrical defect a single parabolic discontinuity line appears. Also in the case of a thin superconducting film exposed to a transverse magnetic field (transverse geometry), a single parabolic discontinuity line has been supposed in the vicinity of a local defect. On the contrary, our investigations show that the flux and current distribution around a single defect in a superconducting thin film can be determined not by a single, but by two discontinuity parabolas. In thin superconducting films in transverse geometry screening currents in the Meissner region (j<jc) are present in contrast to extended infinitely long samples in the longitudinal geometry. We explain our experimental results by the influence of these Meissner screening currents on the temporal formation of the shape of an approaching flux front.

Source-reported materials — not catalogue approval

FormulaReported Tc (K)Pressure (GPa)Type
YBa2Cu3O7-δ

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89Pressure not reportedunknown
YBa2Cu3O7

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Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

89Pressure not reportedunknown
Bi2Sr2CaCu2O8

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—Pressure not reportedunknown
Bi2Sr2CaCu2Ox

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—Pressure not reportedunknown

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