  In this work we present a study of the structural properties of Fe$_{100-x}$
Ga$_x$ grown by Molecular Beam Epitaxy on Mg0(100). We combine long range and
local/chemically selective X-ray probes (X-ray Diffraction and X-ray absorption
spectroscopy) together with real space imaging by means of Transmission
Electron Microscopy and surface sensitive $in situ$ Reflected High Energy
Electron Diffraction. For substrate temperature $T_s$ below 400 $^o$C we obtain
$bcc$ films while, for $x \approx$ 24 and $T_s \geq$ 400$^o$C the nucleation of
the $fcc$ phase is observed. For both systems a Ga anticlustering or local
range ordering phenomenon appears. The Ga/Fe composition in the first and
second coordination shells of the $bcc$ films is different from that expected
for a random Ga distribution and is close to a D0$_3$-like ordered phase,
leading to a minimization of the number of Ga-Ga pairs. On the other side, a
true long-range D0$_3$ phase is not observed indicating that atomic ordering
only occurs at a local scale. Overall, the epitaxial growth procedure presented
in this work, first, avoids the formation of a long range ordered D0$_3$ phase,
which is known to be detrimental magnetostrictive properties, and second,
demonstrates the possibility of growing $fcc$ films at temperatures much
smaller than those required to obtain bulk $fcc$ samples.
