The effect of non-hydrostatic strain on the superconducting properties of in-situ formed Cu-Nb3Sn filamentary composites

The effect of both hydrostatic and nonhydrostatic strains on the intrinsic properties of A15 compounds is well known; however, because of the experimental difficulties the underlying mechanisms are only poorly understood. In this study, we make use of the large elastic strains in the in-situ formed Cu-Nb3Sn filamentary composites due to differential thermal contraction. These strains can be greatly reduced by plastically deforming the sample and hence one can measure the properties of otherwise identical samples in two distinctly different stress states. The increase (upon deformation) in Hc2(2.1 Tesla) and in Tc(0.6K) is correlated with small but significant changes in the low-temperature heat capacity data. These changes are attributed to the increase in the density of states of Nb3Sn phase rather than to the lattice heat capacity. Changes in the critical current Icare shown to be entirely due to the increase in Hc2.