  Effects of Fe-substitution on the crystal structure and magnetic correlations
of the geometrically frustrated antiferromagnets YBaCo4-xFexO7+{\delta} (x = 0,
0.2, 0.4, 0.5, 0.6, and 0.8) have been studied by neutron diffraction,
M\"ossbauer spectroscopy, and ac susceptibility. The compounds
YBaCo4-xFexO7+{\delta} have a special layered-type crystal structure with an
alternating Kagom\'e (6c site) and triangular (2a site) layers along the c
axis. Fe3+ ions are found to be substituted at both the crystallographic 2a and
6c sites of Co ions. M\"ossbauer results show a high spin state of Fe3+ ions in
a tetrahedral coordination. A reduction in the distortion of the Kagom\'e
lattice has been observed with the Fe-substitution. The correlation length of
the short-range antiferromagnetic ordering decreases with the Fe-substitution.
The sharpness of the magnetic transition also decreases with the
Fe-substitution.
