  We present an enhanced diffusion of nuclear spin polarization in fractional
quantum Hall domain phases at $\nu = 2/3$. Resistively-detected NMR mediated by
electrically driven domain-wall motion is used as a probe of local nuclear
polarization, manifesting pumping-dependent signal saturation behavior. This
reveals that a relatively homogeneous polarization profile spreads even to
places distant from pinning centers of the domain walls. We attribute this to
the fact that the pumped nuclear polarization near the domain walls rapidly
diffuses into the domains where nuclei experience Knight fields on comparable
levels. The anomalous enhancement of nuclear diffusion may be interpreted in
terms of indirect hyperfine-mediated interaction between nuclear spins in the
domains.
