First-principles study of magnetization relaxation enhancement and   spin-transfer in thin magnetic films
  The interface-induced magnetization damping of thin ferromagnetic films in contact with normal-metal layers is calculated from first principles for clean and disordered Fe/Au and Co/Cu interfaces. Interference effects arising from coherent scattering turn out to be very small, consistent with a very small magnetic coherence length. Because the mixing conductances which govern the spin transfer are to a good approximation real valued, the spin pumping can be described by an increased Gilbert damping factor but an unmodified gyromagnetic ratio. The results also confirm that the spin-current induced magnetization torque is an interface effect. 
M. Zwierzycki (1), Y. Tserkovnyak (2), P.J. Kelly (1), A. Brataas (3),   G.E.W. Bauer (4) ((1) University of Twente, The Net...