Tunneling transport in ferromagnet/insulator/ferromagnet junctions

We study the spin-dependent transport in expitaxial Ferromagnet/Insulator/Ferromagnet junctions. Firstly we show that the tunneling through the insulator can be described by the complex band structure of the insulator in the gap region, i.e. by the metal-induced gap states. Since the imaginary part of the Bloch vector describes the decay of the wave function, we calculate the spectrum of the decay parameters K for several semiconductors. For large thicknesses the state with the smallest K-value dominates the current. In the second part we present the results of ground state calculation for Fe/ZnSe/Fe(001) and related junctions. We obtain a rather localized charge transfer from the interface Fe layer to the neighbouring semiconductor layer, which is largest for the low-valent termination. Moreover we find that the local moments at the interface depend sensitively on the lattice parameter chosen. Finally, we show that in the minority band at E-F an Fe interface state exists, which deeply penetrates into the barrier