We investigate and discuss the effects of interfacial oxidation on electronic structures and tunnel conductance of the Co2MnSi/MgO/ Co2MnSi(001) magnetic tunnel junction (MTJ) on the basis of first-principles calculations. It is found that the MnSi termination tends to be oxidized compared with the Co termination because of the relaxation of atomic positions in the MnSi-terminated interface. Furthermore, we found that the single oxide layer inserted on both sides of the junction greatly decreases the tunnel conductance of the MTJ in parallel magnetization. We concluded that the relaxation of the Mn atomic position in the oxidized junction reduces the coupling of the Δ1 states between the Co2MnSi electrode and the MgO barrier and causes significant interfacial scattering of the majority-spin electrons with Δ1symmetry at the oxidized layer.
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