BCC Fe, (Ga,Mn)As and (Ga,Mn)N epitaxial films are important candidates for electrical spin injection from a ferromagnet (FM) into a semiconductor (SC). Most of the properties of Fe/GaAs heterostructures can be correlated with the delicate interface formation during epitaxy and its possible modification during subsequent processing. However, the two ternary alloys do need a more detailed understanding of their distinct magnetic and electronic properties and their correlation with the alloy formation mechanisms during growth. Our results show that the Zener model cannot account for the observed electronic and magnetic properties. (C) 2002 Elsevier Science B.V. All rights reserved.