Effect of oxygen contamination on structural and magnetic properties of MnPd bilayer grown on Fe/MgO(001): Ab initio study

We present a detailed study of oxygen contamination on the structural and magnetic properties for both Fe/MgO(001) substrate and MnPd bilayer grown on Fe/MgO(001) by using a plane wave self consistent field (PWscf) method based on DFT and DFT+U approaches, where a generalized gradient correction for exchange-correlation potential is taken into account. For the clean ( $$\hbox {Mn}_{0.5}$$ Mn 0.5 $$\hbox {Pd}_{0.5}$$ Pd 0.5 ) $$_{2}$$ 2 bilayer grown on Fe/MgO(001) substrate, we have found that the c(2x2)-MnPd/c(2x2)-MnPd arrangement, where the magnetic moments of the Mn (Pd) atoms belonging to the surface and subsurface of 4.61 (0.05 $$\mu _{B}$$ μ B ) and -4.03 (0.21 $$\mu _{B}$$ μ B ), is lowest in energy than the c(2x2)-MnPd/p(1x2)-MnPd, p(1x2)-MnPd/MnPd-c(2x2) and p(1x2)-MnPd/p(1x2)-MnPd arrangements. A ripple is obtained at the surface (subsurface) plane. The contamination by O (1-ML coverage) on top for both Fe/MgO(001) and MnPd/Fe(100) multilayers increases interlayer distances between the surface and subsurface layers, with a preferential adsorption of oxygen atoms on the fourfold hollow sites when both DFT and DFT+U approaches are used. Similar magnetic ordering is obtained for Fe/MgO(001) and O/Fe/MgO(001) as well as for (MnPd) $$_{n}$$ n /Fe(100) and O/(MnPd) $$_{n}$$ n /Fe(001) sytems, where n=1-2, taking into account both approaches. The DFT+U approach produces an enhancement of the magnetic moments but does not modify the magnetic ground states of those systems. Here, we found that one half of oxygen atoms is pushed out-of-plane while the other half penetrates the MnPd (Fe) surface, giving rise to the MnO (FeO) oxide surface, in agreement with available experimental data. Graphic Abstract