Measurements of critical data for some type II superconductors and comparison with theory

Hechler, K.; Horn, G.; Otto, G.; Saur, E.

doi:10.1007/bf00628332

Cited by 54 publications

(11 citation statements)

References 16 publications

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“…For theoretical connections to the fundamental parameters, as well as for corrections of the applied approximations, physically more exact descriptions have been developed [48][49][50][51][52] and applied. 1,17,53,54 These more exact descriptions all result, however, in an increased number of fitting parameters, the details of which are impossible to obtain for real, inhomogeneous wire samples. We therefore propose the use of the more simple MDG fit as an acceptable alternative for empirical descriptions of wire data.…”

Section: The Use Of the Mdg Descriptionmentioning

confidence: 99%

“…For wires, 0 H c2 ͑T͒ data are available in limited fields [15][16][17][18][19][20] while few publications report single high-field points at liquid-helium temperature. 17,18,[21][22][23] Extrapolation of data measured up to 22 T indicates a zero-temperature upper critical field ͓ 0 H c2 ͑0͔͒ in thin films ranging from 26 to 29 T, depending on resistivity.…”

Section: Introductionmentioning

confidence: 99%

“…17,18,[21][22][23] Extrapolation of data measured up to 22 T indicates a zero-temperature upper critical field ͓ 0 H c2 ͑0͔͒ in thin films ranging from 26 to 29 T, depending on resistivity. 1,2 Single-and polycrystal data, measured over the complete field range, indicate either 0 H c2 ͑0͒Ϸ24.5 T for the tetragonal phase or 29 T for the cubic phase.…”

Section: Introductionmentioning

confidence: 99%

“…1,2 Single-and polycrystal data, measured over the complete field range, indicate either 0 H c2 ͑0͒Ϸ24.5 T for the tetragonal phase or 29 T for the cubic phase. 3,4 The limited amount of wire 0 H c2 ͑0͒ data, mostly extrapolated from 4.2 K, ranges from about 20 T up to Ͼ30 T. 17,18,[21][22][23] This large spread causes confusion as to what value is to be regarded as realistic in multifilamentary conductors and was a prime motivation for us to make a more systematic study of the influence of the inhomogeneities that are present in wires. We believe that the broad range of performance boundaries for wires in the literature is mostly a side effect of property distributions caused by these inhomogeneities, combined with the use of either arbitrary or variable criteria for 0 H c2 .…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the zero-temperature Kramer 14 -extrapolated critical field ͓ 0 H K ͑0͔͒ often results in values far beyond 30 T. 10 This seems unrealistically high in comparison to actual measured results, which are limited to about 29.5 T for higher resistivity, slightly Sn-poor pure Nb-Sn film. 2 Expressions for the H-T phase transition, derived directly from the BCS theory, are readily available in the literature, [44][45][46][47][48][49][50][51][52] and have been applied with success to welldefined laboratory specimens, 1,17,53,54 but most of the H-T data on wires are empirically described. 36,37,41 This leads to continuing discussions in the literature, partly resulting from the use of extrapolated values of 0 H c2 ͑0͒ without taking into account the inhomogeneous nature of the conductors.…”

Section: Introductionmentioning

confidence: 99%

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The upper critical field of filamentary Nb3Sn conductors

Godeke

Jewell

Fischer

et al. 2005

Journal of Applied Physics

104

128

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We have examined the upper critical field of a large and representative set of present multifilamentary Nb 3 Sn wires and one bulk sample over a temperature range from 1.4 K up to the zero-field critical temperature. Since all present wires use a solid-state diffusion reaction to form the A15 layers, inhomogeneities with respect to Sn content are inevitable, in contrast to some previously studied homogeneous samples. Our study emphasizes the effects that these inevitable inhomogeneities have on the field-temperature phase boundary. The property inhomogeneities are extracted from field-dependent resistive transitions which we find broaden with increasing inhomogeneity. The upper 90%-99% of the transitions clearly separates alloyed and binary wires but a pure, Cu-free binary bulk sample also exhibits a zero-temperature critical field that is comparable to the ternary wires. The highest 0 H c2 detected in the ternary wires are remarkably constant: The highest zero-temperature upper critical fields and zero-field critical temperatures fall within 29.5± 0.3 and 17.8± 0.3 K, respectively, independent of the wire layout. The complete field-temperature phase boundary can be described very well with the relatively simple Maki-DeGennes model using a two-parameter fit, independent of composition, strain state, sample layout, or applied critical state criterion.

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Section: The Use Of the Mdg Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The upper critical field of filamentary Nb3Sn conductors

Godeke

Jewell

Fischer

et al. 2005

Journal of Applied Physics

104

128

View full text Add to dashboard Cite

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Metallkundliche Möglichkeiten zur Erhöhung der Sprungtemperatur zur Supraleitung von A15-Phasen

Wiesinger

1977

Phys. Stat. Sol. (a)

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Eine Bedingung fur maximale Sprungtemperaturen von A15-Phasen ist die stochiometrische Zusammensetzung A,B. Bei Abweichung von dieser fa11t die Sprungtemperatur innerhalb des Homogenitatsbereiches linear ab. Verschiedene A15-Phasen haben einen Homogenitatsbereich, der die stochiometrische Zusammensetzung nicht einschlieat. Fur diese werden demzufolge zu niedrige Sprungtemperaturen gemessen und durch Annaherung an die stochiometrische Zusammensetzung konnen Sprungtemperaturerhohungen erreicht werden. Es wird gepruft, a n welchen Phasen und in welchem MaBe das moglich sein konnte. Dazu werden alle A15-Phasen mit ihren Sprungtemperaturen, Valenzelektronenkonzentrationen und Zusammensetzungen der Phasengrenzen des Homogenitatsbereiches zusammengestellt.A condition for maximum transition temperatures of A15-phases is the stoichiometric composition A,B. With deviation from the stoichiometry the transition temperature drops linearly within the homogeneity range. Various A15-phases have a homogeneity range which does not include the stoichiometric composition. Hence for these phases too low transition temperatures are measured, by approximation to the stoichiometric composition, however, increases of the transition temperatures may be reached. It is investigated which phases are suited and to which extent i t is possible. For this end all A15-phases as well as their transition temperatures, valence-electron concentrations, and the compositions of the phase boundaries of the homogeneity range.are compiled.

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