First-principles theory of quantum well resonance in double barrier magnetic tunnel junctions...

Quantum well (QW) resonances in Fe(001)/MgO/Fe/MgO/Fe double barrier magnetic tunnel junctions are calculated from the first-principles. By including the Coulomb blockade energy due to the finite size islands of the Fe middle layer, we confirm that the oscillatory differential resistance observed in a recent experiment, T. Nozaki et al, Phys. Rev. Lett. {\bf 96}, 027208 (2006), originates from the QW resonances from the $\Delta_1$ band of the Fe majority spin channel. The primary source of smearing at low temperatures is shown to be the variation of the Coulomb blockade energy.