Transport properties of Fe/GaAs/Ag(001) system

We present results of ab initio transport calculations for epitaxial magnetic tunnel junctions Fe/GaAs/Ag(001). The electronic structure is calculated by means of the tight-binding linear muffin-tin orbital method and the ballistic conductances are evaluated within the Kubo-Landauer formalism which includes the effect of the spin-orbit interaction. Particular attention is paid to the dependence of the conductances on the orientation of magnetization direction of the Fe electrode with respect to the crystal lattice and on the thickness of the tunneling barrier. We have found that the in-plane tunneling anisotropic magnetoresistance (TAMR) exhibits a non-monotonic thickness dependence with a maximum around 7.5 nm of GaAs. This behavior is ascribed to a hybridization of interface resonances formed on both sides of the junction and manifested as hot spots in k[]-resolved conductances. For thicker GaAs barriers, the relative intensity of the hot spots is reduced on account of the contribution from a narrow central region of the two-dimensional Brillouin zone which leads to the final decrease of the TAMR effect.