  We investigated electronic structure and magnetic anisotropy in the Fe/MgO
interface of magnetic metal and dielectric insulator under the Cr layer of
small electronegativity, by means of the first-principles density functional
approach. The result indicates that the interface resonance state gets occupied
unlike a typical rigid band picture as the number of Fe layers decreases,
finding large perpendicular anisotropies in the oscillating behavior for
thickness dependence. We discuss scenarios of the two dimensional van Hove
singularity associated with flat band dispersions, and also the accuracies of
anisotropy energy in comparison with the available experimental data.
