Spin pumping and magnetization dynamics in ferromagnet–Luttinger liquid junctions

We study spin transport between a ferromagnet (FM) with time-dependent magnetization and a conducting carbon nanotube or quantum wire, modeled as a Luttinger liquid (LL). The precession of the magnetization vector of the ferromagnet due, for instance, to an outside applied magnetic field causes spin pumping into an adjacent conductor. Conversely, the spin injection causes increased magnetization damping in the ferromagnet. We find that, if the conductor adjacent to the ferromagnet is a Luttinger liquid, spin pumping/damping is suppressed by interactions, and the suppression has clear Luttinger-liquid power-law temperature dependence. We apply our result to a few particular setups. First we study the effective Landau-Lifshitz-Gilbert (LLG) coupled equations for the magnetization vectors of the two ferromagnets in a FM-LL-FM junction. Also, we compute the Gilbert damping for a FM-LL and a FM-LL-metal junction.