Magnetoresistance of Dilute Alloys

Measurements of the negative magnetoresistance in high fields of dilute Au-Mn and Au-Fe alloys reveal a qualitative difference between the anomalous scattering of the conduction electrons by manganese impurities and by iron impurities. The measurements were carried out on a series of alloys with impurity concentrations from 0.11 to 1.01 at.% Fe and 0.22 to 1.20 at.% Mn in pulsed magnetic fields up to 200 kOe and in the temperature range from 2.19 to 50°K. Whereas the effective exchange model of the $s-d$ scattering is adequate in the case of Au-Mn, it fails to account for the anomalous features of the temperature and field dependence of the magnetoresistance in Au-Fe. Furthermore, the magnetoresistance of Au-Fe exhibits an unexpectedly strong concentration dependence which was not observed in Au-Mn and which could not be explained by any magnetic ordering of the Fe impurities. Moreover, the decrease of the zero-field resistivity due to short-range order has been calculated from the magnetoresistance and is found to be consistent with the location of the maximum of the zero-field resistivity.