Spin torque from tunneling through impurities in a magnetic tunnel junction

We study impurity-mediated transport in a magnetic tunnel junction (MTJ) in the sequential tunneling regime. We address the conductance of the MTJ as well as the spin transfer torque. We show that the torque from impurity-mediated tunneling can be distinguished from that from direct tunneling through its dependence on the barrier thickness and the angle between the ferromagnetic moments.