Effect of epitaxial strain on the interfacial electronic properties of MgO/Fe(001): An Ab initio study

The electronic properties of epitaxially strained MgO/Fe(001) interfaces were studied using ab initio electronic structure calculations based on the density functional theory. In epitaxially stacked Fe/MgO/Fe(001) magnetic tunnel junctions, the top Fe/MgO interface can be described by the strained MgO/Fe(001) interfaces. The calculations in this study showed that epitaxial strain influences the electronic properties of interfacial Fe between the Fe and the MgO films: For tensile strain, the spin-minority interfacial peak state near Fermi energy shifts upwards in energy, for compressive strain downwards. When the MgO/Fe(001) system is under 4.6 % tensile strain corresponding to a lattice constant of bulk MgO, the energy shift of the peak state was 0.3 eV. The interfacial spin-minority density of states at the Fermi energy dropped to a third of the unstrained value. This indicates that epitaxial strain, in addition to interfacial atomic structures or structural disorder, can play an important role in spin-dependent tunneling.