  The electronic and magnetic structures in the normal and superconducting
states of iron pnictides are investigated by solving self-consistently the
Bogoliubov-de Gennes equation. It is shown that strong electron correlations
can induce domain walls, which separate regions with different spin density
wave orders. At zero or low electron doping, $90^\circ$ domain walls are formed
while anti-phase domain walls are produced at higher electron doping. On the
domain walls, larger electron densities are always present. The results agree
qualitatively with recent observations of scanning tunneling microscopy and
superconducting quantum interference device microscopy.
