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

Resonant tunneling due to spin－dependent quantum well (QW) states in magnetic tunnel junctions have significant potential in research and applications. We discuss recent theoretical research on QW resonances in Fe(001)/MgO/Fe/MgO/Fe double barrier magnetic tunnel junctions. By calculating these QW states from first-principles and including the Coulomb blockade energy due to the finite size islands of the middle Fe film, we confirm that the oscillatory differential resistance observed in a recent experiment (Nozaki T et al. Phys. Rev. Lett., 2006,96: 027208 )originates from the QW resonances from the Δ1 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.