First-principles analysis of spin-disorder resistivity of Fe and Ni

Spin-disorder resistivity of Fe and Ni and its temperature dependence are analyzed using noncollinear density functional calculations within the supercell method. Different models of thermal spin disorder are considered, including the mean-field approximation and the nearest-neighbor Heisenberg model. If the local moments are kept frozen at their zero-temperature values, very good agreement with experiment is obtained for Fe but for Ni the resistivity at elevated temperatures is significantly overestimated. Agreement with experiment for Fe is improved if the local moments are made self-consistent. The effect of short-range order on spin-disorder resistivity is more pronounced in Ni compared to Fe but it is too weak to explain the overestimation of the resistivity for paramagnetic Ni; the latter is therefore attributed to the reduction in the local moments down to 0.35 mu(B). Overall, the results suggest that low-energy spin fluctuations in Fe and Ni are better viewed as classical rotations of local moments rather than quantized spin fluctuations that would require an (S+1)/S correction.