Spin-dependent quantum well effect in fully epitaxial Cr/ultrathin Fe/MgO/Fe magnetic tunnel junctions

The spin-dependent quantum well effect on tunneling conductance was investigated in fully epitaxial Cr/ultrathin Fe/MgO/Fe junctions at room temperature. We found that the quantum well states (QWS) are strongly affected by the growth condition of the ultrathin Fe layer. Large enhancement of the conductance peak height was observed for the sample with post-annealing temperature 200 °C compared with the case of no annealing. The conductance at around zero bias exhibits clear oscillatory behavior depending on the ultrathin Fe thickness.

► A spin-dependent quantum well effect was observed.
► Quantum well states are affected by the growth condition of the ultrathin Fe layer.
► The ultrathin Fe thickness dependence of conductance at zero bias exhibits oscillation.
► The 1 ML shift of the resonant peak position may be attributed to the FeO free layer structure.