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We discuss the form of the damping of magnetic excitations in a metal near aferromagnetic instability. The paramagnon theory predicts that the damping termshould have the form $\Omega/\Gamma (q)$ with $\Gamma (q) \propto q$ (theLandau damping). However, the experiments on uranium metallic compounds UGe$_2$and UCoGe showed that $\Gamma (q)$ tends to a constant value at vanishing $q$.A non-zero $\Gamma (0)$ is impossible in systems with one type of carriers(either localized or itinerant) because it would violate the spin conservation.It has been conjectured recently that a non-zero $\Gamma (q)$ in UGe$_2$ andUCoGe may be due to the presence of both localized and itinerant electrons inthese materials, with ferromagnetism involving predominantly localized spins.We present microscopic analysis of the damping of near-critical localizedexcitations due to interaction with itinerant carriers. We show explicitly howthe presence of two types of electrons breaks the cancellation between thecontributions to $\Gamma (0)$ from self-energy and vertex correction insertionsinto the spin polarization bubble and discuss the special role of theAslamazov-Larkin processes. We show that $\Gamma (0)$ increases with $T$ bothin the paramagnetic and ferromagnetic regions, but in-between it has a peak at$T_c$. We compare our theory with the available experimental data.

Non-Landau damping of magnetic excitations in systems with localized and itinerant electrons