Interface magnetic moments enhancement of FePt-L1$_0$/MgO(001): an ab-initio study

The interface between FePt--L1$_0$ and MgO(001) alloys has been studied using density functional calculations. Because the stacking of the face-centered tetragonal L1$_0$ phase is formed by alternating Fe and Pt planes, both the Fe- and Pt-terminated contact layers were studied. Furthermore, due to the large mismatch between the in-plane lattice constants of both systems, we have chosen some common $a$ values for both alloys in order to explore in detail the adsorption energy, the electronic structure and the interface magnetism. The adsorption energy has been calculated by subtracting the energy of clean FePt and MgO alloys from the total energy. The preferred adsorbed geometric sites for Fe/Pt atoms are when they lie on $top$ of the O species, having a smaller adsorption energy for the remaining positions. We found that expanding the MgO lattice enhances the magnetic moment of the Fe species but the Pt moments remain almost constant.