Magneto-optical investigation of flux penetration in a superconducting ring

Pannetier, M.; Klaassen, F.M.; Wijngaarden, Rinke J.; Welling, M. S.; Heeck, K.; Huijbregtse, J.M.; Dam, B.; Griessen, R.

doi:10.1103/physrevb.64.144505

Cited by 22 publications

(22 citation statements)

References 21 publications

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“…2͑d͒ is qualitatively not different from the one observed in the experiment for a pure superconducting ring of Ref. 23. Nor from the simulated profiles of a bare superconductor, shown for comparison in Fig.…”

Section: Simulations and Discussioncontrasting

confidence: 37%

“…1͑b͒ and 1͑c͒ whereas its outer edge becomes dark, indicating a small magnetic field. This situation is exactly the opposite from what is observed for a superconducting ring without a magnetic layer, 23 where the local field is large ͑and parallel to the applied field͒ at the outer edge and small at the inner edge.…”

mentioning

confidence: 57%

“…This self-field is parallel to the applied field at the outer edge of the ring and antiparallel at its inner edge. 23 Hence, the z component of the local field at the outer edge of the ring is enhanced while it is reduced at its inner edge. The corresponding simulated field pattern is given in Fig.…”

Section: Simulations and Discussionmentioning

confidence: 98%

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Magnetization rotation in a superconductor/ferromagnet bilayer ring structure

et al. 2009

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The magnetic-flux distribution in a bilayer ring consisting of superconducting Nb and ferromagnetic amorphous Gd 19 Ni 81 is studied at low temperature by magneto-optical imaging. The ring is macroscopic with an outer diameter of 500 m and an inner diameter of 300 m. Below the superconducting transition and with a small magnetic field applied along the ring axis, we observe a field enhancement at the inner edge and a field reduction at the outer edge, opposite to what is observed for a bare superconducting ring. With help from numerical simulations we show this to be due to an in-plane rotation of the magnetization of the Gd 19 Ni 81 layer toward the radial direction, under the influence of shielding currents in the superconductor. In the superconductor, the resulting stray field of the magnetic layer is in the same direction as the field due to the superconducting shielding currents. As a consequence, these shielding currents are reduced. Alternatively, for a fixed critical current, the superconductor will be able to withstand a larger external field if coated by the magnetic material; it is hardened by it.

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Section: Simulations and Discussioncontrasting

confidence: 37%

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confidence: 57%

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Magnetization rotation in a superconductor/ferromagnet bilayer ring structure

et al. 2009

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“…In particular, for the tube, the component B z is negative near the opening and close to the inner boundary, as seen in the dashed circle of figure 5(b). Such a behaviour is reminiscent of the field distribution found in the proximity of a thin ring [35][36][37][38].…”

Section: Modelling Of the Field Penetration Into A Hts Tubementioning

confidence: 69%

Spectra of quantum systems in superstrong inertial force fields

Денисов¹,

Kravtsov²

2002

Quantum Electron.

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We have experimentally studied the magnetic shielding properties of a cylindrical shell of BiPbSrCaCuO subjected to low frequency AC axial magnetic fields. The magnetic response has been investigated as a function of the dimensions of the tube, the magnitude of the applied field and the frequency. These results are explained quantitatively by employing the method of Brandt (1998 Phys. Rev. B 58 6506) with a J c (B) law appropriate for a polycrystalline material. Specifically, we observe that the applied field can sweep into the central region either through the thickness of the shield or through the opening ends, the latter mechanism being suppressed for long tubes. For the first time, we systematically detail the spatial variation of the shielding factor (the ratio of the applied field over the internal magnetic field) along the axis of a high-temperature superconducting tube. The shielding factor is shown to be constant in a region around the centre of the tube, and to decrease as an exponential in the vicinity of the ends. This spatial dependence comes from the competition between two mechanisms of field penetration. The frequency dependence of the shielding factor is also discussed and shown to follow a power law arising from the finite creep exponent n.

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“…Thus, these measurements are restricted both by the surface S of the weld and by its quality j w which, in turn, imposes the lowest-temperature margin. On the other hand, prevalent contactless methods ͑e.g., levitation force technique, 9,19 magneto-optical image analysis, 9,17,22 scanning Hall-sensor magnetometry, [8][9][10][11][12][13][14][15] and magnetization loop studies 8,9,18,23 ͒ are not free of ambiguities in the processing of experimental data unless, as mentioned above, the welded sample has the shape of a thin ring. In this case, the circular current throughout a ring is limited by the weakest link which is, in turn, usually associated with a joint.…”

Section: Introductionmentioning

confidence: 99%

Intergrain and intragrain currents in bulk melt-grownYBa2Cu3O7

Surzhenko¹,

Zeisberger²,

Habisreuther³

et al. 2003

Phys. Rev. B

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A simple contactless method suitable for discerning between the intergrain ͑circular͒ current, which flows in the thin superconducting ring, and the intragrain current, which does not cross the weakest link, has been proposed. At first, we show that the intergrain current may directly be estimated from the magnetic flux density B(Ϯz 0 ) measured by the Hall sensor positioned in the special points Ϯz 0 above or below the ring center. The experimental and numerical techniques to determine the value z 0 are discussed. Being very promising for the characterization of a current flowing across the joints in welded YBaCuO rings ͑its dependences on the temperature and external magnetic field as well as the time dissipation͒, the approach has been applied to study the corresponding properties of the intragrain and intergrain currents flowing across the a-twisted grain boundaries which are frequent in bulk melt-textured ͑MT͒ YBaCuO samples. We present experimental data related to the flux penetration inside a bore of MT YBaCuO rings both in the nonmagnetized, virgin state, and during the field reversal. The shielding properties and their dependence on external magnetic fields are also studied. Besides, we consider flux creep effects and their influence on the current redistribution during a dwell.

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Magneto-optical investigation of flux penetration in a superconducting ring

Cited by 22 publications

References 21 publications

Magnetization rotation in a superconductor/ferromagnet bilayer ring structure

Magnetization rotation in a superconductor/ferromagnet bilayer ring structure

Spectra of quantum systems in superstrong inertial force fields

Intergrain and intragrain currents in bulk melt-grownYBa2Cu3O7

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