Effect of an interfacial oxygen monolayer on the spin-polarization at the Fe/MgO interface: First-principles calculations

Abstract

Density functional theory is applied to calculate the structural, electronic, and magnetic properties of the Fe/MgO/Fe (001) magnetic tunnel junctions (MTJs) as well as the influence of an interfacial oxygen monolayer by the addition of oxygen atoms at the Fe/MgO interface. The formation of Fe–O bonded atoms, as well as the changes in the spin polarization around the Fermi level of the Fe/MgO/Fe (001) with an interfacial FeO layer, is observed. The calculated spin-polarized density of states of the Fe/MgO/Fe with a Fe–O interface layer showed that the peaks of the O 2s, O 2p, and Fe 3d states are shifted due to the coupling between the O atoms and Fe layer. The Fe/MgO/Fe structure exhibits metallic behavior due to the position of the density of states (DOS) peak at the Fermi level with both majority and minority spins. The calculated spin polarization (P) is only 7% for the metallic Fe/MgO/Fe structure, whereas the metallic Fe/MgO/Fe structure with FeO interfacial layer has P of 24%. Thus, the polarization is found to be extremely sensitive to the nature of the interface layer. Likewise, the nature of spin-charge transfer in both investigated MTJ structures was found to be different at the Fe/MgO interface due to the hybridization interaction between Fe and O. We have also calculated the structural, magnetic, and electronic properties of Fe/MgO/Fe with FeO layer with different sizes of the junction by varying the number of MgO layers, with Fe thickness fixed at 5 ML.