  Nuclear electric resonance (NER) is based on nuclear magnetic resonance
mediated by spatial oscillations of electron spin domains excited by a radio
frequency (RF) electric field, and it allows us to investigate the spatial
distribution of the nuclear spin polarization around domain walls (DWs). Here,
NER measurements were made of the dynamic nuclear spin polarization (DNP) at
the spin phase transition of the fractional quantum Hall state at a Landau
level filling factor of $\nu=2/3$. From the RF pulse power and pulse duration
dependence of the NER spectrum, we show that the DNP occurs only within $\sim
100$ nm around DWs, and that it does not occur in DWs. We also show that DWs
are pinned by the hyperfine field from polarized nuclear spins.
