Optimum condition for spin-current generation from magnetization precession in thin film systems

The generation efficiency of spin currents induced by a magnetization-precession motion in a thin film system has been investigated in terms of a magnetization-precession trajectory. By using the Landau–Lifshitz–Gilbert equation combined with the phenomenological model of the spin pumping, the generation efficiency is calculated to be equal to the elliptical orbit area of magnetization precession, which is maximized when the precession trajectory is distorted. This calculation well reproduces experimental results on the magnetization-angle dependence of the inverse spin-Hall signal induced by the spin pumping in a Ni81Fe19/Pt bilayer film.