Epitaxial Fe films, with thickness in the range between 2.5 and 12 Angstrom
, were grown in UHV conditions on the 7 x 7 reconstructed (111)-Si surface,
with a Cu 35 Angstrom thick buffer layer, using the so-called metal-metal
epitaxy on silicon (MMES). Kikuchi electron diffraction showed that the gro
wth of Fe on Cu/Si(111) occurs first by formation of a pseudomorphic film o
f gamma-Fe(111), about two to three atomic layers thick, and by the success
ive growth of bcc Fe(110) domains in the Kurdjumov-Sachs orientation, in ag
reement with our previous low-energy electron diffraction observations. Ker
r effect measurements carried out at low temperatures (20-150 K) revealed t
hat Fe films thinner than 5-6 Angstrom are ferromagnetic with an easy axis
magnetization orthogonal to the film plane. With increasing Fe thickness, i
n coincidence with the fcc-to-bcc structural transformation, the easy axis
switches to the in-plane orientation over a finite range of thickness. (C)
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