Many physical effects are strongly depending on the composition of the interfaces between separating layers. Hence, the knowledge of the interfacial characteristics such as structure, chemical bonds, or magnetic properties of the corresponding materials is essential for an understanding and optimization of these effects. This study reports on a combined magnetic and structural analysis using X-ray photoelectron diffraction (XPD) and transverse magneto-optical Kerr effect (T-MOKE). The information depth of these methods is demonstrated by investigating the uppermost GaAs(001) layer beneath a Fe-film and the interfacial regimes of Fe/GaAs( 001) beneath an MgO capping layer. Iron was prepared on a clean GaAs(001) surface and a GaAs(001)-(4 x 2)-reconstructed surface. Beneath the Fe-film, the (4 x 2)-reconstruction is not lifted, which is clearly shown by the diffraction pattern of the GaAs(4 x 2)-Fe surface. It is shown that Fe inter-diffusion, resulting in an amorphous interface, is almost prevented by the Ga-rich reconstruction. The magneto-optical measurements with T-MOKE clearly demonstrated the Fe-interlayer in a ferromagnetic state. We find no evidence for magnetic properties neither within the signal of the GaAs-substrate nor the MgO-film. (C) 2016 Elsevier B.V. All rights reserved.