  Iron oxides are among the most abundant compounds on Earth and have
consequently been studied and used extensively in industrial processes. Despite
these efforts, concrete understanding of some of their surface phase structures
has remained elusive, in particular the oxidized ${\alpha}-Fe_2O_3(0001)$
hematite surface. We detail an optimized recipe to produce this phase over the
entire hematite surface and study the geometrical parameters and composition of
its complex structure by means of atomically resolved microscopy, electron
diffraction and surface-sensitive spectroscopies. We conclude that the oxidized
${\alpha}-Fe_2O_3(0001)$ surface is terminated by a two-dimensional iron oxide
with structure, lattice parameters, and orientation different from the bulk
substrate. Using total-energy density functional theory for simulation of a
large-scale atomic model, we identify the structure of the surface layer as
antiferromagnetic, conductive $1T-FeO_2$ attached on half-metal terminated
bulk. The model succeeds in reproducing the characteristic modulations observed
in the atomically resolved images and electron diffraction patterns.
