Gap anisotropy and electron-phonon interaction in dilute Al-Mg alloys

The resistivity of dilute AlMg is measured between 0 and 90 degrees C for Mg concentrations up to 8 at.%. From these results and McMillan's formula (1968), a value for the change of the superconducting transition temperature, Tc, with Mg concentration is calculated which is found to describe accurately the observations in the whole solid solution range outside the gap anisotropy region, ie from about 2 to 18 at.% Mg. In the gap anisotropy region an attempt is made to analyse the depression of Tc by a combination of the Markowitz-Kadanoff theory and the resistivity measurements. The results suggest that the Markowitz-Kadanoff parameter (1963) can be obtained quantitatively by this approach.