The determination of collective spin excitations and their contribution to the intrinsic resistivity via spin-flip electronic scattering are addressed for $3d$ ferromagnets using magnetotransport experiments. We present longitudinal high-field magnetoresistance (MR) measurements from 4 to 500 K and up to 40 T on Fe-, Co-, and Ni-patterned thin films. Well above the technical saturation of the magnetization—i.e., in the paraprocess regime—we report an almost linear and nonsaturating negative MR of around 0.01–0.03 μΩ cm ${\mathrm{T}}^{\mathrm{-}1}$ at 300 K for the three magnets. We demonstrate its magnetic origin, and we assign this high-field resistivity decrease to the electron-magnon scattering and the spin-wave damping in high fields. We propose a theoretical calculation of the magnetic resistivity originating from spin-flip intraband $s-s$ and $d-d$ and interband $s-d$ transitions via electron-magnon diffusion including both the high-field effect on the magnon spectrum and the magnon mass renormalization. Convincing agreements between the high-field measurements and our model provide a unique estimate of the pure magnetic resistivity in $3d$ ferromagnets. Our analysis also gives an insight into the low-energy spin waves—i.e., the theoretical magnon saturation field and the magnon mass renormalization consistent with neutron scattering results for the three magnets.

• Received 26 November 2001

DOI:https://doi.org/10.1103/PhysRevB.66.024433