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

TL;DR

This study uses first-principles calculations to analyze how spin disorder affects electrical resistivity in Fe and Ni, revealing the importance of local moments and spin fluctuations in their temperature-dependent behavior.

Contribution

It provides a detailed first-principles analysis of spin-disorder resistivity in Fe and Ni, comparing models and highlighting the role of local moments and spin fluctuations.

Findings

Good agreement with experiment for Fe when local moments are self-consistent.

Overestimation of resistivity in Ni due to reduced local moments at high temperatures.

Spin fluctuations are better modeled as classical rotations of local moments.

Abstract

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. Spin-disorder resistivity is found to depend weakly on magnetic short-range order. 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 iterated to self-consistency. The overestimation of the resistivity for paramagnetic Ni is attributed to the reduction of the local moments down to 0.35 Bohr magnetons. 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.