Nonlinear domain-wall dynamics in a system of two magnetic layers

The nonlinear dynamics of the magnetization in a spin-valve structure is investigated. Equations describing the dynamics of the magnetization in such a structure are obtained. The stability of the solution corresponding to a motionless flat domain wall is investigated. The nonlinear domain-wall dynamics are investigated in the approximation of a strong exchange interaction between the magnetic layers and in the approximation of a large magnetostatic energy. In the former case the nonlinear dynamical equations are shown to be similar to the equations describing the dynamics of the magnetization in a weak ferromagnet, and in the latter case they are similar to the equations of motion of a magnetic vortex (i.e., a vertical Bloch line) in a domain wall.