Ultrathin half metallic N and antiferromagnetic semiconducting C layers on MgO(001)

Abstract

Using the full potential linearized augmented plane wave (FLAPW) method, we have exploredthe magnetic properties of ultrathin C and N layers on a MgO(001) surface. It has been foundthat the free standing C layer has a ferromagnetic (FM) ordering with a magnetic moment of0.82 μB, while the free standing N layer with the same coverage displaysan antiferromagnetic (AFM) state with a magnetic moment of1.68 μB. Through a structure optimization procedure, we have found that both C and N adatomsare adsorbed on the O-top position in the presence of a MgO(001) surface. The ultrathin0.25 monolayer coverage of C/MgO(001) film becomes a magnetic semiconductor and shows thec(2 × 2) AFM ground state with a magnetic moment of0.62 μB.Surprisingly, the ultrathin N/MgO(001) manifests a half metallic state with a magnetic moment of0.47 μB. In addition, the induced spin polarization in the O atom is found and this hybridizationsignificantly affects the density of states (DOS) behavior. This peculiar DOS feature results inthe opposite magnetic ground states of C and N layers on a MgO(001) surface. Additionally, itis found that the N/MgO(001) has a perpendicular magnetocrystalline anisotropy energy of63 µeV. We also present theoretically calculated x-ray absorption spectroscopy (XAS) and x-raymagnetic circular dichroism (XMCD) results.