Tunnel magnetoresistance in ferromagnetic double-barrier planar junctions: coherent tunneling regime

Coherent tunneling in a double-barrier system consisting of two external ferromagnetic electrodes and a nonmagnetic central one is studied theoretically within the free-electron approximation. It is shown that the junction resistance depends on the relative orientation of magnetic moments of the ferromagnetic electrodes (so-called tunnel magnetoresistance). The magnetoresistance vs. thickness of the central electrode shows pronounced peaks related to the resonant tunneling through the whole system. Variation of the magnetoresistance with bias voltage is also studied. This variation is generally nonmonotonous