Resistivity from magnetic impurity pairs in metallic alloys

Abstract

The spin-flip contributions to the electron scattering by a pair of magnetic impurities is found to exhibit a ${T}^{\mathrm{\ensuremath{-}}1}$ behavior in the temperature variation of the cross section. Our calculations provide an explanation for the sharp decrease in the low-temperature resistivities of several alloys in the intermediate concentration regime where the Kondo effect is inoperative and the Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling between impurities is substantial. Accordingly, the size and magnitude of the impurity pair contribution to the resistivity is a senstive function of the impurity concentration and the electronic structure of the host metal. Our computations agree with the data of ${\mathrm{CuMn}}_{\mathrm{x}}$, ${\mathrm{AgMn}}_{\mathrm{x}}$, ${\mathrm{AuMn}}_{\mathrm{x}}$, and ${\mathrm{AuCr}}_{\mathrm{x}}$, and they predict the observed variation of the resistivity maximum with impurity concentration using a standard RKKY coupling between impurities.