Resonant Magnetoresistance in Asymmetric Double-Barrier Magnetic Tunnel Junctions

Resonant tunneling is studied theoretically for the planar asymmetrical double-barrier magnetic tunnel junction (DMTJ) when a dc bias field is applied. The spin-polarized conductance and tunnel magnetoresistance (TMR) through the DMTJ have been calculated. In DMTJ nanostructure the magnetization of middle ferromagnetic metal layer can be aligned parallel or antiparallel with respect to the fixed magnetizations of the top and bottom ferromagnetic electrodes. Analytical expression for the transmission coefficient of the DMTJ is received, which is expressed through the single-barrier transmission coefficients taking into account the voltage drop on each barrier and spin degrees of freedom of the electron. The dependencies of the tunnel conductance and TMR on the applied voltage have been calculated for the case of resonant transmission.