Limiting Velocity and Dispersion Law of Domain Walls in Ferrimagnets Close to the Spin Compensation Point

The motion of domain walls in GdFeCo-type ferrimagnets near the point of compensation of sublattice spins s1 and s2, when the effects of the exchange increase in the limiting wall velocity take place, is theoretically studied. The energy E and momentum P of the wall are determined and the dispersion relation E = E(P) is derived. It is found that some walls become unstable at a sufficiently small decompensation value s1 - s2 νc(s1 + s2), this dispersion relation, as well as that for ferromagnets, is periodic.