Site random superconductivity of A15 compound Nb3Sn induced by mechanical milling

Abstract

We performed mechanical milling of the A15-type superconductor Nb3Sn with transition temperature Tc = 18K. Tc decreased with increasing milling time, a result similar to that of Di, Loeff and Bakker, except that Tc seemed to decrease discontinuously with milling time. X-ray diffraction (XRD) patterns were taken using a conventional X-ray diffractometer with CuKa radiation at room temperature. The height of the Bragg peaks lowered and their width broadened after milling, but the patterns of the A15 structure persisted for up to 48 h of milling. We compared the XRD patterns of Nb3Sn with simulations using REATAN-2000, and obtained evidence that the site random disorder of Nb and Sn atoms in the A15 structure caused the decrease in Tc.