Current and field pattern in rectangular and inhomogeneous superconductors

Schuster, Thomas; Kühn, H.; Brandt, Ernst Helmut; Indenbom, M. V.; Kläser, M.; Müller‐Vogt, G.; Habermeier, H.–U.; Kronmüller, H.; Forkl, A.

doi:10.1103/physrevb.52.10375

Cited by 94 publications

(62 citation statements)

References 43 publications

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“…As a result, there is no cushion pattern observed in high-T c superconducting materials. 13 This observation is consistent with magnetization loops at low field region where the magnetization drops rapidly once over the magnetization peak. The easy vortex motion along the intergranular path was also demonstrated in Fig.…”

Section: 12supporting

confidence: 87%

Magnetic flux penetration in polycrystalline SmFeO0.75F0.2As

Lin

Zhu

et al. 2010

Journal of Applied Physics

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The recently discovered Fe-As superconducting materials which show high potential ability to carry current due to their low anisotropy have attracted a great number of attentions to understand their superconductivity mechanism and explore their applications. This paper presents a method to synthesis SmFeO 0 . 75 F 0.20 As polycrystalline by hot press in detail. The magnetization at different temperatures and applied fields obtained by a superconducting quantum interference device are also discussed. In addition, the local magnetization process is presented by magneto-optical imaging technique at the conditions of zero-field-cooling and fieldcooling. It is found that the collective magnetization process of the newly discovered Fe-As superconductors is very similar to that of high-T c cuprates. For instance, the Fe-As superconductors and high-T c cuprates have the same magnetization features due to strong pining and intergrain weak link. The global supercurrent is significantly lower than local grain supercurrent due to the weak line between the grains. The recently discovered Fe-As superconducting materials which show high potential ability to carry current due to their low anisotropy have attracted a great number of attentions to understand their superconductivity mechanism and explore their applications. This paper presents a method to synthesis SmFeO 0.75 F 0.20 As polycrystalline by hot press in detail. The magnetization at different temperatures and applied fields obtained by a superconducting quantum interference device are also discussed. In addition, the local magnetization process is presented by magneto-optical imaging technique at the conditions of zero-field-cooling and field-cooling. It is found that the collective magnetization process of the newly discovered Fe-As superconductors is very similar to that of high-T c cuprates. For instance, the Fe-As superconductors and high-T c cuprates have the same magnetization features due to strong pining and intergrain weak link. The global supercurrent is significantly lower than local grain supercurrent due to the weak line between the grains.

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Section: 12supporting

confidence: 87%

Magnetic flux penetration in polycrystalline SmFeO0.75F0.2As

Lin

Zhu

et al. 2010

Journal of Applied Physics

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“…Hence, large n means small creep, and the Bean critical state model 1 is regained in the limit n → ∞. For numerical simulations of flux penetration into the strip we use the formalism developed by Brandt 4,9,[11][12][13][14][15][16][17] that can be applied to thin type-II superconductors of various shapes. For a thin superconductor, it is appropriate to look at length scales larger than the thickness d, and introduce a sheet current…”

Section: Modelmentioning

confidence: 99%

Flux penetration in a superconducting strip with an edge indentation

et al. 2007

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The flux penetration near a semicircular indentation at the edge of a thin superconducting strip placed in a transverse magnetic field is investigated. The flux front distortion due to the indentation is calculated numerically by solving the Maxwell equations with a highly nonlinear E(j) law. We find that the excess penetration, ∆, can be significantly (∼ 50 %) larger than the indentation radius r0, in contrast to a bulk supercondutor in the critical state where ∆ = r0. It is also shown that the flux creep tends to smoothen the flux front, i.e. reduce ∆. The results are in very good agreement with magneto-optical studies of flux penetration into an YBa2Cu3Ox film having an edge defect.

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“…8 The equation was solved for the cases of quadratic, rectangular samples, 8 crosslike samples, and quadratic samples with semicircular indents. 9 A different situation arises if the superconducting thin film contains nonconducting regions which are not connected to the sample edge and which are large enough that they act not solely as a pinning center, but screening currents must flow around them. A model for the current and magnetic flux distribution in the critical state around a circular nonconducting defect in type-II superconductors was given by Campbell and Evetts.…”

Section: Introductionmentioning

confidence: 99%

“…Time-dependent solutions were given for superconducting thin films with different shapes of boundaries. 8,9 Unfortunately, only the sample boundaries have been varied and geometries of nonconducting areas within a superconducting media have not been considered.…”

mentioning

confidence: 99%

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

et al. 2001

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The magnetic flux penetration into thin type-II superconducting films with circular defects is investigated. The artificial circular defects ͑diameter ϭ40 m) in an YBa 2 Cu 3 O 7Ϫ␦ thin film ͑thickness Ϸ300 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 geometry͒ 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 geometry͒, 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 ( jϽ j c ) 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.

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Current and field pattern in rectangular and inhomogeneous superconductors

Cited by 94 publications

References 43 publications

Magnetic flux penetration in polycrystalline SmFeO0.75F0.2As

Magnetic flux penetration in polycrystalline SmFeO0.75F0.2As

Flux penetration in a superconducting strip with an edge indentation

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

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