Exact solution of the Boltzmann equation for low-temperature transport coefficients in metals. II. Scattering by ferromagnons

In a previous paper (Paper I) we developed a technique for exactly solving the linearized Boltzmann equation for the electrical and thermal transport coefficients in metals in the low-temperature limit. Here we adapt this technique to determine the magnon contribution to the electrical and thermal conductivities, and to the thermopower, in metallic ferromagnets. For the electrical resistivity rho at asymptotically low temperatures we find rho proportional to exp (-T-min/T), with T-min an energy scale that results from the exchange gap and a temperature-independent prefactor of the exponential. The corresponding result for the heat conductivity is sigma(h) proportional to T-3 exp (T-min/T), and thermopower is S proportional to T. All of these results are exact, including the prefactors.