The Role of Spin-Dependent Interface Scattering in Generating   Current-Induced Torques in Magnetic Multilayers
  We present a calculation of current-induced torques in metallic magnetic multilayers derived from the spin-dependent transmission and reflection properties of the magnetic layers. A scattering formalism is employed to calculate the torques in a magnetic-nonmagnetic-magnetic trilayer, for currents perpendicular to the layers, in both the ballistic and diffusive regimes. 
Xavier Waintal, Edward B. Myers, Piet W. Brouwer, and D. C. Ralph