  To investigate correlation effects on antiferromagnetic order in Fe
pnictides, we apply a variational Monte Carlo method to a two-orbital model. We
obtain a small ordered moment consistent with experimental observations even
for a Coulomb interaction comparable to the band width. Studies of estimation
of the Coulomb interaction for Fe pnictides suggest values comparable to or
slightly smaller than the band width, and much larger ordered moments have been
obtained by the Hartree-Fock approximation for such a large Coulomb
interaction. Thus, the correlation effect is important for Fe pnictides at
least quantitatively.
