Temperature Dependence of the Electrical Resistivity of Dilute Ferromagnetic Alloys

We present a theoretical discussion of the contribution to the temperature-dependent portion of the electrical resistivity from electron-magnon scattering in dilute ferromagnetic alloys. The transport relaxation rate may be written as a sum of two terms, one (the coherent part) which arises from wave-vector-conserving electron-magnon scattering, and a second (the incoherent part) arises from wave-vector-nonconserving scattering processes. The incoherent part is found to be proportional to $T^{\frac{3}{2}}$, and to the impurity concentration, at low concentrations. We also present new data on the temperature dependence of the electrical resistivity of dilute NiMn alloys. A term proportional to $T^{\frac{3}{2}}$ and to the Mn concentration is observed. We suggest that this term arises from the incoherent scattering of conduction electrons by magnons. The general features of the incoherent contribution to the resistivity relaxation rate are discussed. We have also applied the theory to the ferromagnetic alloys PdFe and PdMn to extract the concentration dependence of the spin-wave stiffness constant $D$. The results suggest that the Mn moment is localized at the impurity cell and its near vicinity, in contrast to the well-known giant character of the moment associated with Fe and Co in Pd.