  In this paper, we elaborate analytical theory of domain wall dynamics close
to the angular momentum compensation point based on non-linear dynamic
equations derived from the effective Lagrangian of a ferrimagnet. Analysis of
the precession angle and domain wall velocity oscillations in post Walker
regime in a ferrimagnet is performed. In the framework of the proposed model,
we explore dynamic processes in the Walker and post Walker regimes. We show
that although spin oscillations quench the dynamics of domain walls near the
Walker breakdown field, a further increase of the driving magnetic field
increases domain wall speed and mobility. An anomalous behavior of domain wall
dynamic properties near the angular momentum compensation point in ferrimagnets
is discussed.
