  Using density functional theory, we carried out systematic calculations for a
series of ultrathin iron layers with thicknesses ranging from one atomic
monolayer to eleven monolayers (up to about 1.5 nm). We considered three cases:
(1) iron layers both on a gold substrate and coated with gold, (2) iron layers
on a gold substrate but without coverage, and (3) freestanding iron layers
adjacent to a vacuum. For our models, we chose initial bcc Fe(001) surfaces and
fcc Au(001) substrates. Based on the calculations, we determined the details of
the geometry and magnetic properties of the systems. We calculate lattice
parameters, magnetic moments, Curie temperatures and magnetocrystalline
anisotropy energies. From the thickness dependence, we determined the volume
and surface contributions to the magnetic anisotropy constant. The further
analysis allowed us to determine the thickness ranges of the occurrence of
perpendicular magnetic anisotropy, as well as the effect of thickness and the
presence of a substrate and cap layer on the direction of the magnetization
easy axis.
