Strong depression of Tc in superconducting disordered Cu50Zr50 with dilute magnetic impurities

Dilute magnetic impurities in a superconducting metallic glass are investigated. For two alloys with 1650 ppm of iron and with 11 ppm of manganese in a Zr50Cu50 host, there is a comparable reduction of the superconducting Tc by 40–50%. The upper critical field is measured for both samples down to t = T/Tc < 0.15 and the magnetic susceptibility is measured for the manganese-doped sample down to 2 K. From these measurements we conclude that there is strong pairbreaking in both alloys, which appears to decrease slightly with decreasing temperature. The manganese impurity has a spin of S = 2 and a Curie-Weiss temperature of −3.8 K, and an unusually strong effect on Tc with a depression rate of about 350 K (at.%)−1.