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.