Spin-orbital Gilbert damping in common magnetic metals

Understanding the damping of fast magnetization precession in ferromagnetic metals is important for many applications. Spin-orbital effective fields fluctuating as a result of electron collisions with the lattice defects are known to cause magnetic damping of the Gilbert type. Formulas convenient for numerical estimates derived using exact linear-response theory are discussed in terms of the Fermi golden rule. Estimates of the damping rates in Fe and Ni based on band structures matched to ab initio calculations and on the lifetime approximation account for a substantial part of the experimental values. The relevance of the lifetime approximation is discussed and supported by a simple model calculation.