Magneto-optical studies of the uniform critical state in bulk MgB<sub>2</sub>

Polyanskii, Anatolii; Gurevich, A.; Jiang, J.; Larbalestier, D. C.; Bud’ko, S.L.; Finnemore, D. K.; Lapertot, G.; Canfield, Paul C.

doi:10.1088/0953-2048/14/10/301

Cited by 27 publications

(24 citation statements)

References 25 publications

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“…Given these promising results combined with weak current blocking by grain boundaries [97], the lack of electromagnetic granularity [98], and very slow thermally-activated flux creep [99,100], it is not surprising that MgB 2 is being regarded as a strong contender of traditional high-field magnet materials like NbTi and Nb 3 Sn. Despite these achievements, a detailed theory of pinning in MgB 2 is trill lacking.…”

Section: Discussionmentioning

confidence: 99%

Limits of the upper critical field in dirty two-gap superconductors

Gurevich

2007

Physica C: Superconductivity

175

189

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An overview of the theory of the upper critical field in dirty two-gap superconductors, with a particular emphasis on MgB2 is given. We focus here on the maximum Hc2 which may be achieved by increasing intraband scattering, and on the limitations imposed by weak interband scattering and paramagnetic effects. In particular, we discuss recent experiments which have recently demonstrated ten-fold increase of Hc2 in dirty carbon-doped films as compared to single crystals, so that the Hc2(0) parallel to the ab planes may approach the BCS paramagnetic limit, Hp[T ] = 1.84Tc[K] ≃ 60 − 70T . New effects produced by weak interband scattering in the two-gap Ginzburg-Landau equations and Hc2(T ) in ultrathin MgB2 films are addressed.

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Section: Discussionmentioning

confidence: 99%

Limits of the upper critical field in dirty two-gap superconductors

Gurevich

2007

Physica C: Superconductivity

175

189

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“…The relative lower J c in this study may be due to the fact A magneto-optical image of an air quenched MgB 2 slab demonstrates that almost no spatial variation of J c is visible. 2,18 This suggests that there is no inherent string suppression of current across the grain boundaries. Obviously, the current percolation behavior in the quenched MgB 2 is determined by the nanodomains that constituted the subgrains in the clusters.…”

mentioning

confidence: 99%

Intrinsic nanostructural domains: Possible origin of weaklinkless superconductivity in the quenched reaction product of Mg and amorphous B

Prabhakar

Tan

et al. 2002

Applied Physics Letters

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Smooth modulation structure of Mg–B alloy in the quenched reaction product of Mg and amorphous B was studied. It indicates that the MgB2 formed possibly in spinodal decomposition, thus resulting in MgB2 nanodomains. It was found that the nanodomains with small angle boundaries of atomic-scale width were distributed within the subgrains that constitute the clusters in MgB2 grains. This nanostructural characteristic may be intrinsic in the quenched reaction product of Mg and amorphous B. It makes the nanodomain boundaries not act as barriers to the current percolation path, thus exhibiting no weak-link problem in the MgB2.

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“…around entire regions consisting of many tiny grains, indicating a lack of any weak links between the grains. Many subsequent studies have confirmed this conclusion [24]- [26]. Subsequent experiments [27] have found that it is even possible to obtain high J c values in powder-in-tube wires by rolling without subsequent sintering.…”

Section: J C and Flux Pinningmentioning

confidence: 82%

Potential application of magnesium diboride for accelerator magnet applications

Cooley

Eom²,

Hellstrom³

et al.

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)

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This paper reviews the potential of the newly discovered and unexpected 39 K superconductor MgB 2 as a material for accelerator magnet strands. Unlike the high temperature cuprate superconductors, intergranular current flow in MgB 2 is not obstructed by weak links, removing one serious obstacle to the fabrication of wires. The critical current density J c exceeds 10 5 A/cm 2 in 1 T field at 4.2 K and in self-field at 20 K. However, the compound is anisotropic and the perpendicular upper critical field H c2^ in present bulk samples is comparable to or less than that in Nb47wt.%Ti at 4.2 K. Thin films have shown significantly higher J c and H c2 . Magnetization J c values at 4.2 K exceed 10 6 A/cm 2 in many reports, and approach 10 7 A/cm 2 for films with T c close to 39 K. In alloyed films with small grain size and high resistivity, the irreversibility field H* (~0.85H c2 ) is 16 T at 4.2 K in perpendicular field (and double that in parallel field), and J c exceeds 10 5 A/cm 2 up to 10 T at 4.2 K and 5 T at 20 K. Simple wires, which achieve the properties of sintered bulk samples, are being made by the powder-in-tube route, indicating potential application capability, particularly if alloyed MgB 2 wires replicating thin film properties can be made.

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Magneto-optical studies of the uniform critical state in bulk MgB₂

Cited by 27 publications

References 25 publications

Limits of the upper critical field in dirty two-gap superconductors

Limits of the upper critical field in dirty two-gap superconductors

Intrinsic nanostructural domains: Possible origin of weaklinkless superconductivity in the quenched reaction product of Mg and amorphous B

Potential application of magnesium diboride for accelerator magnet applications

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Magneto-optical studies of the uniform critical state in bulk MgB2

Cited by 27 publications

References 25 publications

Limits of the upper critical field in dirty two-gap superconductors

Limits of the upper critical field in dirty two-gap superconductors

Intrinsic nanostructural domains: Possible origin of weaklinkless superconductivity in the quenched reaction product of Mg and amorphous B

Potential application of magnesium diboride for accelerator magnet applications

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Magneto-optical studies of the uniform critical state in bulk MgB₂