Tunnel magnetoresistance in ferromagnetic junctions: Tunneling through a single discrete level - art. no. 085318

Tunnel magnetoresistance in a double-barrier junction with ferromagnetic el ectrodes, and a quantum dot (or a single atom) as the central part, is anal yzed theoretically in the sequential-tunneling regime. The magnetoresistanc e is due to the rotation of magnetic moments of external electrodes from an tiparallel to parallel alignment. The considerations are restricted to the case of a single discrete level, with Coulomb correlations and spin-flip tr ansitions included. The tunneling current and occupation numbers are calcul ated for both magnetic configurations. It is shown that electron correlatio ns at the dot can enhance the magnetoresistance effect, and give rise to a diodelike behavior. Spin-flip processes, on the other hand, suppress the ma gnetoresistance, and reduce the magnetically induced asymmetry in the curre nt-voltage characteristics with respect to the bias reversal.