Domain instability during precessional magnetization reversal

Spin wave equations in the non-equilibrium precessing state of a ferromagnetic system are found. They show a spin-wave instability towards growing domains of stable magnetization. Precession of the uniform magnetization mode is described by the Landau Lifshitz equation with the exponentially growing in time effective Gilbert dissipation constant that could have both signs. On the developed stages of the domain instability a non-stationary picture of domain chaos is observed.