  We report on the interplay of two uniaxial magnetic anisotropies in epitaxial
Fe thin films of varying thickness grown on InAs(001) as observed in
ferromagnetic resonance experiments. One anisotropy originates from the Fe/InAs
interface while the other originates from in-plane shear strain resulting from
the anisotropic relaxation of the Fe film. X-ray diffraction was used to
measure the in-plane lattice constants of the Fe films, confirming the
correlation between the onset of film relaxation and the corresponding shear
strain inferred from ferromagnetic resonance data. These results are relevant
for ongoing efforts to develop spintronic and quantum devices utilizing large
spin-orbit coupling in III-V semiconductors.
