Magnetic anisotropies of epitaxial ultrathin iron films grown on the surface-reconstructed GaAs substrate were studied. Ferromagnetic
resonance technique was exploited to determine magnetic parameters of
the films in the temperature range of 4-300 K. Extraordinary angular
dependence of the FMR spectra was explained by the presence of fourfold
and twofold in-plane anisotropies. A strong in-plane uniaxial
anisotropy with magnetic hard axis along the [1 (1) over bar0]
crystallographic direction is present at the GaAs/Fe(001) interface
while a weak in-plane uniaxial anisotropy for the Fe grown on Au has
its easy axis oriented along [1 (1) over bar0]. A linear dependence
of the magnetic anisotropies as a function of temperature suggests that
the strength of the in-plane uniaxial anisotropy is affected by the
magnetoelastic anisotropies and differential thermal expansion of
contacting materials. (c) 2007 American Institute of Physics.