Spatially resolved studies of chemical composition, critical temperature, and critical current density of a YBa2Cu3O7−δ thin film

Gaevski, Mikhail; Bobyl, A. V.; Shantsev, D. V.; Suris, R. A.; Tret’yakov, V. V.; Galperin, Y. M.; Johansen, T. H.

doi:10.1063/1.368758

Cited by 8 publications

(6 citation statements)

References 16 publications

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“…In contrast, for continuously varying |j|, e.g. for a local field dependence of j c (B), or continuously varying transition temperatures (Gaevski et al 1998), no splitting of the current pattern into domains of different magnitudes can occur. We will consider now the case where the magnitude of the current density is sharply varying in an area, where the boundary condition for the sample requires a uniform current flow parallel to the sample edge.…”

Section: Domain Boundaries With Perpendicular Currentsmentioning

confidence: 96%

Magneto-optical studies of current distributions in high-T_csuperconductors

et al. 2002

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In the past few years magneto-optical flux imaging (MOI) has come to take an increasing role in the investigation and understanding of critical current densities in high-T c superconductors (HTS). This has been related to the significant progress in quantitative high-resolution magnetooptical imaging of flux distributions together with the model-independent determination of the corresponding current distributions. We review in this article the magneto-optical imaging technique and experiments on thin films, single crystals, polycrystalline bulk ceramics, tapes and melt-textured HTS materials and analyse systematically the properties determining the spatial distribution and the magnitude of the supercurrents. First of all, the current distribution is determined by the sample geometry. Due to the boundary conditions at the sample borders, the current distribution in samples of arbitrary shape splits up into domains of nearly uniform parallel current flow which are separated by current domain boundaries, where the current streamlines are sharply bent. Qualitatively, the current pattern is described by the Bean model; however, changes due to a spatially dependent electric field distribution which is induced by flux creep or flux flow have to be taken into account. For small magnetic fields, the Meissner phase coexists with pinned vortex phases and the geometry-dependent Meissner screening currents contribute to the observed current patterns. The influence of additional factors on the current domain patterns are systematically analysed: local magnetic field dependence of j c (B), current anisotropy, inhomogeneities and local transport properties of grain boundaries. We then continue to an overview of the current distribution and current-limiting factors of materials, relevant to technical applications like melt-textured samples, coated conductors and tapes. Finally, a selection of magneto-optical experiments which give direct insight into vortex pinning and depinning mechanisms are reviewed.

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Section: Domain Boundaries With Perpendicular Currentsmentioning

confidence: 96%

Magneto-optical studies of current distributions in high-T_csuperconductors

et al. 2002

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“…At least it is known that non-stoichiometric films prepared with molecular chemical vapour deposition (MOCVD) have a stoichiometric YBCO matrix with nonstoichiometric precipitates [3] and that Y-rich and Bapoor films have high J c [4]. However, there are also contradicting results showing that J c has a maximum near the stoichiometric 123 composition [5][6][7]. Therefore it is difficult to find a simple rule for how non-stoichiometric metallic compositions actually affect the value of J c in thin YBCO films.…”

Section: Introductionmentioning

confidence: 99%

Reason for high critical current in thin YBCO films prepared by laser ablation from nanostructured target

Paturi¹,

Huhtinen²,

Laajalehto³

et al. 2000

Supercond. Sci. Technol.

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Thin YBCO films prepared by laser ablation from a nanocrystalline target have a high critical current density Jc≈107 A cm-2 at 77 K. To clarify the reason for the high value of Jc, the composition and structure of these films are compared with those deposited from a typical coarse-grained target. According to energy-dispersive x-ray and photoelectron spectroscopic analysis the contents of Y, Ba and Cu are similar in the films of both origins, despite some differences in the compositions of the targets. It is concluded that the high value of Jc in the films prepared from the nanocrystalline target can be explained by pinning of magnetic flux vortices to extended structural defects.

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“…It may be caused, e. g., by a nonuniform chemical composition. 21 The kind of deviation shown in Fig. 4 can be explained by a suppressed j c near the strip edge.…”

Section: Discussionmentioning

confidence: 93%

Symmetry of the remanent-state flux distribution in superconducting thin strips: Probing the critical state

et al. 2001

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The critical-state in a thin strip of YBa 2 Cu 3 O 7Ϫ␦ is studied by magneto-optical imaging. The distribution of magnetic flux density is shown to have a specific symmetry in the remanent state after a large applied field. The symmetry was predicted ͓Phys. Rev. Lett. 82, 2947 ͑1999͔͒ for any j c (B), and is therefore suggested as a simple tool to verify the applicability of the critical-state model. At large temperatures we find deviations from this symmetry, which demonstrates a departure from the critical-state behavior. The observed deviations can be attributed to an explicit coordinate dependence of j c since both a surface barrier and flux creep would break the symmetry in a different way.

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Spatially resolved studies of chemical composition, critical temperature, and critical current density of a YBa2Cu3O7−δ thin film

Cited by 8 publications

References 16 publications

Magneto-optical studies of current distributions in high-T_csuperconductors

Magneto-optical studies of current distributions in high-T_csuperconductors

Reason for high critical current in thin YBCO films prepared by laser ablation from nanostructured target

Symmetry of the remanent-state flux distribution in superconducting thin strips: Probing the critical state

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Spatially resolved studies of chemical composition, critical temperature, and critical current density of a YBa2Cu3O7−δ thin film

Cited by 8 publications

References 16 publications

Magneto-optical studies of current distributions in high-Tcsuperconductors

Magneto-optical studies of current distributions in high-Tcsuperconductors

Reason for high critical current in thin YBCO films prepared by laser ablation from nanostructured target

Symmetry of the remanent-state flux distribution in superconducting thin strips: Probing the critical state

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Product

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Magneto-optical studies of current distributions in high-T_csuperconductors

Magneto-optical studies of current distributions in high-T_csuperconductors