We report on the magnetic and structural characterization of Au/(Ni)Fe/MgO/Fe magneto-tunnel junctions grown on InP(001) and GaAs(001). On GaAs substrates almost perfect single crystal junctions with sharp interfaces were achieved as seen by low energy electron diffraction and transmission electron microscopy. In situ magnetization loops obtained with the longitudinal magneto-optic Kerr effect show an independent switching of magnetization of both Fe layers suggesting that the two Fe layers are magnetically decoupled by the MgO layer.