  We propose and analyze surface-plasmon-driven electron spin currents in a
thin metallic film. The electron gas in the metal follows the transversally
rotating electric fields of the surface plasmons (SPs), which leads to a static
magnetization gradient. We consider herein SPs in a thin-film
insulator-metal-insulator structure and solve the spin diffusion equation in
the presence of a magnetization gradient. The results reveal that the SPs at
the metal interfaces generate spin currents in the metallic film. For thinner
film, the SPs become strongly hybridized, which increases the magnetization
gradient and enhances the spin current. We also discuss how the spin current
depends on SP wavelength and the spin-diffusion length of the metal. The
polarization of the spin current can be controlled by tuning the wavelength of
the SPs and/or the spin diffusion length.
