  We address damping of a Goldstone spin-rotation mode emerging in a quantum
Hall ferromagnet due to laser pulse excitation. Recent experimental data show
that the attenuation mechanism, dephasing of the observed Kerr precession, is
apparently related not only to spatial fluctuations of the electron Land\'e
factor in the quantum well, but to a hyperfine interaction with nuclei, because
local magnetization of GaAs nuclei should also experience spatial fluctuations.
The motion of the macroscopic spin-rotation state is studied microscopically by
solving a non-stationary Schr\"odinger equation. Comparison with the previously
studied channel of transverse spin relaxation (attenuation of Kerr oscilations)
shows that relaxation via nuclei involves a longer quadratic stage of
time-dependance of the transverse spin, and, accordingly, an elongated
transition to a linear stage, so that a linear time-dependance may not be
revealed.
