Middle-layer ferromagnetism-induced transition of the tunnel magneto-resistance in double-barrier magnetic tunnel junctions: A non-equilibrium Green's function study

Using the non-equilibrium Green's function modeling of the transport characteristics of tunnel devices, we have found the middle-layer ferromagnetism-induced transition of the tunnel magneto-resistance in double-barrier magnetic tunnel junctions. It is observed from our study that even a weak ferromagnetism of the middle metallic layers is capable of promoting resonant tunnel magneto-resistance in these devices and the strength of the ferromagnetism is found to have strong influence on the bias dependence of the resonant tunnel magneto-resistance. The spin-up and spin-down currents flow in opposite directions for certain band occupancies and at certain bias voltage ranges when there is antiferromagnetic coupling between the electrodes of the tunnel junction. Resonant tunnel magneto-resistance occurs when the net current (sum of spin-up and spin-down currents) becomes very small at situations mentioned above. We have further studied the influence of band occupation of the electrode layers and the many-body interactions present in the electrode region on the spin current and magneto-resistance of these devices