Magnon scattering in the transport coefficients of CoFe alloys

Resistivity $\rho$, thermopower ${\cal S}$, and thermal conductivity $\kappa$ were measured simultaneously on a set of CoFe alloy films. Variation of the Co-content $x_\mathrm{Co}$ allows for a systematic tuning of the Fermi level through the band structure, and the study of the interplay between electronic and magnetic contributions to the transport coefficients. While band structure and magnon effects in $\rho$ and $\kappa$ are rather weak, they turn out to be very significant in ${\cal S}$. The evolution of Mott and magnon drag contributions to ${\cal S}$ is traced between the two limiting cases of pure Fe and pure Co. In addition, we find an interesting sign change of the magnon drag.