Superconducting properties variation with A15 composition in Nb3Sn

Abstract

We extend the Ginzburg-Landau-Abrikosov-Gor'kov (GLAG) theory to account for the variation of the upper critical field Hc2 with Sn content in A15-type Nb3Sn. Hc2 at the vicinity of the critical temperature Tc is related quantitatively to the electrical resistivity, specific heat capacity coefficient and Tc, with inclusion of the electron-phonon coupling correction, Pauli paramagnetic limiting and martensitic phase transformation of A15 lattices. Hc2 near Tc is then extrapolated to Hc2(0) at temperature 0K, and Hc2(0) versus tin content agrees well with experiments. We find that, as Sn content gradually approaches the stoichiometry, Nb3Sn undergoes a transition from the dirty limit to clean limit, split by the phase transformation boundary. The H-T phase boundary and the pinning force show different behaviors in the cubic and tetragonal phase. Applying the theoretical formulas in the technical Nb3Sn wire, we obtain the dependence of the composition gradient on the superconducting properties variation in the A15 layer, as well as the curved tail at vicinity of Hc2 in the Kramer plot of the Nb3Sn wire. This gives a better understanding of the inhomogeneous-composition inducing discrepancy between the results by the state-of-art scaling laws and experiments.

References in corpus (7)

• A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State
• A general scaling relation for the critical current density in Nb3Sn
• Refinement of Nb3Sn grain size by the generation of ZrO2 precipitates in Nb3Sn wires
• Internally Oxidized Nb3Sn Strands with Fine Grain Size and High Critical Current Density
• A theory of the strain-dependent critical field in Nb3Sn, based on anharmonic phonon generation
• Formation and upper critical fields of the two distinct A15 phases in the subelements of Powder-In-Tube Nb3Sn wires
• Assessing composition gradients in multifilamentary superconductors by means of magnetometry methods

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• Smooth, homogeneous, high-purity Nb3Sn superconducting RF resonant cavity by seed-free electrochemical synthesis
• Microscopic Investigation of rf Vortex Nucleation in Nb3Sn Films Using a Near-Field Magnetic Microwave Microscope