The paper discusses a novel mechanism for enhanced Gilbert damping in thin ferromagnetic films contacted with normal metal layers. The authors propose that the precession of the magnetization in the ferromagnetic layer acts as a spin pump, transferring angular momentum into the adjacent normal metal layers. This effect is mathematically formulated in terms of the scattering matrix of the ferromagnetic layer, which can be calculated using model or first-principles methods. The damping constant is found to be renormalized by the interface parameters, leading to an increased damping coefficient. The authors estimate the damping coefficient for permalloy thin films and find that it agrees well with recent experimental results. The mechanism explains the trends observed in experiments on permalloy films and provides a theoretical framework for understanding the enhanced Gilbert damping in thin magnetic films.The paper discusses a novel mechanism for enhanced Gilbert damping in thin ferromagnetic films contacted with normal metal layers. The authors propose that the precession of the magnetization in the ferromagnetic layer acts as a spin pump, transferring angular momentum into the adjacent normal metal layers. This effect is mathematically formulated in terms of the scattering matrix of the ferromagnetic layer, which can be calculated using model or first-principles methods. The damping constant is found to be renormalized by the interface parameters, leading to an increased damping coefficient. The authors estimate the damping coefficient for permalloy thin films and find that it agrees well with recent experimental results. The mechanism explains the trends observed in experiments on permalloy films and provides a theoretical framework for understanding the enhanced Gilbert damping in thin magnetic films.