Observation of current-discontinuity lines in type-II superconductors

Schuster, Thomas; Indenbom, M. V.; Koblischka, Michael Rudolf; Kühn, H.; Kronmüller, H.

doi:10.1103/physrevb.49.3443

Cited by 130 publications

(48 citation statements)

References 27 publications

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“…It could be experimentally observed that the magnetic flux distribution around a circular defect in a superconducting thin film cannot be described by a model which was often used in the case of thin films, [11][12][13][14] though it was originally reduced by Campbell and Evetts for a cylindrical defect in an infinitely long sample. 10 We explain our observation by screening currents in the Meissner region ( jϽ j c ) which are present in thin superconducting films exposed to a perpendicular magnetic field in contrast to infinitely long samples exposed to a parallel field.…”

Section: Discussionmentioning

confidence: 99%

“…The parameter p of the parabolic discontinuity line with the equation yϭx 2 /2p corresponds to the defect diameter 2R. Since Schuster and co-workers, 11,12 this model has also been used to describe the influence of circular defects in superconducting thin films. 13,14 In contrast to the sample geometry considered by Campbell and Evetts, the demagnetizing factor of a thin film cannot be neglected, and screening currents flow not only in the outer parts of the sample which are already in the critical state ( jϭ j c ), but also in the central parts even if they are still in the Meissner state ( jϽ j c ).…”

Section: Introductionmentioning

confidence: 99%

“…This could be a reason for observing only a single discontinuity parabola in thin films in the past. [11][12][13][14] Apart from the discussed four defects in the center of Fig. 7, there are two additional ones located on the far lower right-hand side of the upper figure ͑prepared in the same manner͒.…”

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confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2001

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“…Evidently, the excess penetration is not equal to the indentation radius, r 0 , as in the case of the bulk Bean model. 2,3,19 Moreover, ∆ turns out to be fielddependent. Initially, ∆ increases, then reaches a maximum followed by a decrease at larger H a .…”

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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“…In that case, however, it may cost us the reduction of the critical current. So, there is a method of patterning filaments on the HTSC coated conductors to reduce the hysteresis loss while keeping almost the area of conductors [6][7][8][9][10][11][12]. It is required to analyze the sample which is patterned filamentary but most of the measurement method gives information only about the whole sample.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the local superconducting properties in YBCO coated conductors with striations

Kim¹,

Park²,

Park³

et al. 2015

Progress in Superconductivity and Cryogenics

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In order to realize economical applications, it is important to reduce the ac loss of 2G high-temperature superconductor coated conductors. It seems to be reasonable that a multi-filamentary wire can decrease the magnetization loss. In this study, we prepared two samples of YBCO coated conductors with striations. We measured local superconducting properties of both samples by using Low Temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). The distribution of the local critical temperature of samples was analyzed from experimental results of Low Temperature Scanning Laser Microscopy (LTSLM) near the superconducting transition temperature. According to LTSLM results, spatial distributions of the local critical temperature of both samples are homogeneous. The local current density and the local magnetization in samples were explored from measuring stray fields by using Scanning Hall Probe Microscopy (SHPM). From SHPM results, the remanent field pattern of the one bridge sample in an external magnetic field confirms the Bean's critical state model and the three bridge sample has similar remanent field pattern of the one bridge sample. The local magnetization curve in the three bridge sample was measured from external fields from -500 Oe to 500 Oe. We visualized that the distribution of local hysteresis loss are related in the distribution of the remanent field of the three bridge sample. Although the field dependence of the critical current density must be taken into account, the relation of the local hysteresis loss and the remanent field from Bean's model was useful.

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Observation of current-discontinuity lines in type-II superconductors

Cited by 130 publications

References 27 publications

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

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

Flux penetration in a superconducting strip with an edge indentation

Analysis of the local superconducting properties in YBCO coated conductors with striations

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