The resonant interaction of surface acoustic waves and spin waves is a potential new tool to handle information. However, the natural precession frequencies of most ferromagnetic materials lie in the 10 GHz range, i.e. far above present common technology for surface acoustic waves. This feature restricts the range of materials of interest. To expand this range, we present here measurements of the acoustic attenuation and velocity, at room temperature, in epitaxial Fe on GaAs(001). Resonant coupling is observed in the sub-GHz regime by proper selection of the orientation and intensity of the applied magnetic field. With a very simple magnetization dynamics model that takes into account the softening of the magnetic precession modes, we are able to describe the observed salient features.