We report on the growth of single-crystal Fe films by magnetron sputtering onto GaAs substrates. In order to establish the epitaxial orientation with the substrate a 100 Å Cr buffer layer was rf sputtered. The crystalline and magnetic properties were studied by x-ray diffraction, ferromagnetic resonance, and Kerr effect magnetometry techniques. The θ-2θ x-ray measurements show that only the Fe (200) peak is present, and the rocking curve shows a full width half maximum of 2°. Ferromagnetic resonance lines exhibit a line width of about 30 Oe, and the in-plane resonance field as a function of the azimuth angle presents a fourfold symmetry with no induced anisotropy. The in-plane hard- and easy-axis magneto-optical hysteresis loop traces are consistent with the ferromagnetic resonance results. © 1998 American Institute of Physics.