Spin current in the Kondo lattice model
  By using the projection operator technique it is observed that the strong Hund's rule coupling and s-d interaction in transition metal elements may lead to an effective coupling between the spin current and spin spirality. As a result, the spin spirality can be regarded as a driving force to produce a spin current. The spin current may give rise to a novel type of field acting on the spins. A spin battery is designed based on the interactions between the spin current and spin spirality. 
S. Q. Shen and X. C. Xie