Dark and Bright Solitons of Extraordinary Waves in Ferromagnetic Systems

It is shown that the slowly varying amplitudes of both high and low frequency extraordinary waves propagating perpendicular to the dc magnetic field in ferromagnetic systems are described by the nonlinear SchrEdinger equation. The extraordinary waves are modulationally stable (unstable) and may evolve as dark (bright) solitons as the frequency ω satisfies ω₀ < ω < ω_b or ω > ω₁(0 < ω < ω₀ or ω_a ≤ ω < ω₁), where ω_a, ω_b, ω₀ and w₁ are given in the text.