抄録
The change in Tc of the superconducting transition temperature of aluminum due to the addition of 3d transitional impurities Ti, V, Cr, Mn, Fe and Ni is measured as a function of the residual resistance ratio ρ in the region of dilute concentrations ranging from 0.001 to 0.04 atomic percent. The contribution due to the smearing out of the energy gap anisotropy (ΔTc)anis is estimated by assuming that it can be accounted for by the theory of Markowitz and Kadanoff. (ΔTc)anis thus estimated is found to depend only on the mean free path and very little on the type of impurity. The remaining part (ΔTc)v obtained by subtracting (ΔTc)anis from the observed change in the transition temperature, is found to be negative showing a dependence on impurity similar to that found for the residual resistance but differing that it shows a rather sharp minimum at Mn. Comparison with theories based on the Anderson model of localized states in metals are made. It is shown that the overall behavior shows fair agreement with theories which include the effect of the d-d coulomb correlation energy.
