Planar approximation for spin transfer systems with application to   tilted polarizer devices
  Planar spin-transfer devices with dominating easy-plane anisotropy can be described by an effective one-dimensional equation for the in-plane angle. Such a description provides an intuitive qualitative understanding of the magnetic dynamics. We give a detailed derivation of the effective planar equation and use it to describe magnetic switching in devices with tilted polarizer. 
Ya. B. Bazaliy
cond-mat.mtrl-sci