Fe/MgO/Fe/Cr/Fe tunneling structures were epitaxially grown directly on GaAs(001) without buffer layer. Interdiffusion in the Fe/GaAs interface was investigated using conversion electron Mössbauer spectroscopy. An independent magnetization switching in the Fe electrodes was achieved by pinning the magnetization of the Fe-top electrode by antiferromagnetic coupling across a Cr spacer to another Fe film. For transport measurements, optical lithography and ion etching were applied to reduce the junction area. A tunneling magnetoresistance of 10%–12% at room temperature was found.