Semiclassical theory of spin transport in magnetic multilayers

A semiclassical model of the spin momentum transfer in ferromagnetic film (FM)/normal metal (NM) structures is presented. It is based on the Landau-Lifshitz equation of motion and the exchange interaction in FM, and on the spin diffusion equation in NM. The internal magnetic field is treated by employing Maxwell's equations. A precessing magnetization in FM creates a spin current which is described by spin pumping proposed by Tserkovnyak The back flow of spins from NM into FM is assumed to be proportional to the spin accumulation in NM as proposed by Silsbee These theoretical calculations are tested against the experimental results obtained by different groups. A good agreement was found for Py/Cu samples, but spin pumping is significantly enhanced in Py/Pt systems. (C) 2003 American Institute of Physics.