ELECTRONIC DISORDER IN SUPERCONDUCTING AMORPHOUS ZR-CO-P - COMPARISON WITH RESULTS FOR T(C) AND B(C2) OF AMORPHOUS-ALLOYS

The superconducting transition temperature and the upper critical magnetic field of amorphous Zr67Co33-xPx, x = 0, 5, 11, are studied. Comparison of critical-field parameters for several different amorphous alloys show that an anomalously enhanced critical field cannot be simply correlated to other material properties. Results from different methods to increase disorder in three-dimensions are compared. The normalized T(c) of Zr67Co33-xPx samples, and published results for H-doped samples and neutron-irradiated samples all show a similar dependence of the resistivity increase. This relation extends to below 20% of the initial T(c) and it can be obtained from the Fukuyama-Ebisawa-Maekawa theory with a single adjustable parameter. The widths of the superconducting transitions in the magnetic field decrease strongly with decreasing temperature for Zr-Co-P but remain finite at the lowest measuring temperatures. The critical magnetic field increases with increased disorder, which agrees with recent observations from neutron irradiation and cannot be explained by current theories for disorder effects.