The chemical, structural, and electronic properties of MgO/Fe (001) and MgO/Fe (001)− p (1× 1) O interfaces for magnetic tunnel junctions (MTJs) have been widely investigated by means of electron spectroscopy. In particular, we present a detailed analysis of the spin-resolved electronic structure above the Fermi level, carried out by spin-polarized inverse photoemission and absorbed current spectroscopy. The MgO barrier presents good crystallinity and sharp interfaces when grown both onto Fe (001) and Fe (001)− p (1× 1) O. Moreover, we find that the exchange splitting of unoccupied bands is essentially the same for the two MgO/Fe interfaces, even though it is different for the two starting surfaces, being larger in Fe (001)− p (1× 1) O than in Fe (001). Our findings indicate that Fe (001)− p (1× 1) O is a good candidate for the realization of heterostructures for magnetic tunnel junctions because of its high chemical …