Spin injection in double magnetic tunnel junctions: A tight-binding study

Spin current injection in double magnetic tunnel junctions is investigated theoretically based on conservation of spin and charge currents. Numerical calculations are performed for spin accumulation, current density and spin polarization in Fe/insulator (I) (semiconductor (S))/Co/I(S)/Fe double junctions using generalized formalism based on the non-equilibrium Green's function, which are implemented with recursive calculation of real space Green's function in tight-binding model in linear response region. It is shown that spin accumulation leads to difference in resistance, depending on the direction of applied bias with respect to the magnetization configuration of the double barrier magnetic tunnel junctions.