First-Principles Studies of Antiferromagnetic MnO and NiO Surfaces

Surface properties of antiferromagnetic MnO(001) and NiO(001) are investigated by means of first-principles electronic structure calculations. It is shown that the surface O sites have finite spin magnetic moments of 0.04 µ B and 0.07 µ B for MnO and NiO surfaces, respectively. Because of non-zero energy gap even at the surface, the spin magnetic moment of Mn and Ni sites are almost the same as those in bulk. At the surface O sites, calculated spin density shows asymmetric distribution comparing with that of the bulk. These results are explained in detail from calculated partial density of states. By surface structural optimization, stable surface structure of O inward rumpled relaxation is obtained for both monoxides.