A series of Fe thin films with thicknesses ranging from 1 monolayer (ML) to
30 ML was deposited on a Cu90Au10 (001) substrate (a = 3.66 Angstrom) at r
oom temperature. Structural properties were investigated by low-energy elec
tron diffraction (LEED). From intensity vs energy [I(E)] measurements of th
e specular LEED reflection, three different structural phases were observed
. The first phase at low Fe thicknesses (<4 ML) is a tetragonally expanded
fee phase (fct) with an interlayer distance a(<perpendicular to>) above 1.9
0 Angstrom. The second phase at Fe thicknesses between 4 and 10 ML is assoc
iated with an interlayer distance a(perpendicular to) approximate to 1.76 A
ngstrom. With further increasing Fe thickness (>10 ML), the third phase, a
bcc(011) structure with a(perpendicular to) approximate to 2.03 Angstrom, o
ccurs. The magnetic properties were studied by in situ magneto-optical Kerr
effect (MOKE). It was found that the Fe films of the first and third phase
have a high-spin ferromagnetic moment, while they exhibit a low net magnet
ic moment in the second phase. The observed structural and magnetic phases
are thus similar to the Fe/Cu(001) system. The direction of the easy magnet
ic axis in Fe/Cu90Au10 is perpendicular to the film plane only at thickness
es below 2 ML, where a spin-reorientation transition from perpendicular-to-
the-film-plane to in-plane with increasing film thickness has been found. T
he origin of perpendicular magnetization is discussed.