Effect of Spin Current on Uniform Ferromagnetism: Domain Nucleation
  Large spin current applied to a uniform ferromagnet leads to a spin-wave instability as pointed out recently.   In this paper, it is shown that such spin-wave instability is absent in a state containing a domain wall, which indicates that nucleation of magnetic domains occurs above a certain critical spin current.   This scenario is supported also by an explicit energy comparison of the two states under spin current. 
Junya Shibata, Gen Tatara, Hiroshi Kohno