Low photoemission intensity near induced by the surface relaxed structure of CrO2(001).

Based on first principles calculations we find that CrO2(001) will form a relaxed structure at its surface, at which each surface Cr atom is surrounded by four oxygen atoms in a distorted tetrahedral configuration. This tetrahedral environment has important effects on the electronic structure, leading to an inversion of the t2g-eg splitting of Cr 3d orbitals. Two 3d electrons of the surface Cr ion will fully occupy the doublet eg, which becomes lower in energy than the t2g, leaving the t2g orbitals empty. The consequence is that the Fermi level lies in a gap between the eg and t2g for a local electronic structure at the surface. This finding is consistent with and explains the extremely low photoemission intensity near EF at CrO2(001) [Kämper et al., Phys. Rev. Lett. 59, 2788 (1987)].