The tunnel magnetoresistance (TMR) effect was investigated in perpendicularly magnetized magnetic tunnel junctions (p-MTJs) consisting of a stacked layer structure of ultrathin Fe (0.7)/MgO (1.8)/CoFeB (1.2-1.4) (in nm). A relatively large TMR ratio of 95% was obtained with an interface perpendicular magnetic anisotropy energy density of 1.5 mJm-2 at the Fe/MgO interface. Moreover, we found that the p-MTJ exhibits spin-dependent resonant tunnelling characteristics in the bias voltage dependence of differential conductance, corresponding to a quantum well confined in five monolayers of the Fe(0 0 1) atomic plane. The results showed that the resonant tunnelling of Δ1 symmetry electrons through the spin-dependent quantum well can be realized even in a p-MTJ structure with strong perpendicular magnetic anisotropy.
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