MANIFESTATION OF NONCONSERVATION OF MAGNETIZATION MODULUS IN THE STEADY-STATE DOMAIN-WALL MOTION

The influence of the nonconservation of magnetization modulus on the s teady-stale domain wall motion is investigated, The wall motion in the presence of an external field normal to the anisotropy axis is consid ered. The Slonczewski-type equations are derived from the Landau-Lifsh itz equation with relaxation term introduced by Bar'yakhtar. It is sho wn that the nonconservation of magnetization modulus gives a larger co ntribution to the wall drag in ferromagnets with a narrower ferromagne tic resonance line width than in those with a wider line width. It is also shown that the standard Landau-Lifshitz-Gilbert equation gives al most the same results for the wall velocity in ferromagnets with wider resonance line if the value phenomenological relaxation constant is d etermined from domain wall mobility measurements, instead of data on f erromagnetic resonance line width.