A scaling law for the critical current of Nb(sub 3)Sn stands based on strong-coupling theory of superconductivity

The transition temperature T(sub c), the thermodynamic critical field B(sub c), and the upper critical fields B(sub c2) of Nb(sub 3)Sn were numerically calculated by Eliashberg theory of strongly coupled superconductors using the Einstein spectrum. It was found that the impurity concentration was relatively low and the strain effects were due to the phonon mode softening both at high and low frequencies.