Orbital character of O-2p unoccupied states near the Fermi level in CrO2

The orbital character, orientation, and magnetic polarization of the O-2p unoccupied states near the Fermi level (E-F) in CrO2 was determined using polarization-dependent x-ray absorption spectroscopy and x-ray magnetic circular dichroism from high-quality, single-crystal films. A sharp peak observed just above E-F is excited only by the electric-field vector (E) normal to the tetragonal c axis, characteristic of a narrow band (approximate to 0.7 eV bandwidth) constituted from O-2p orbitals perpendicular to c (O-2p(y)) hybridized with Cr 3d(xz-yz) t(2g) states. By comparison with band-structure and configuration-interaction cluster calculations our 3d results support a model of CrO2 as a half-metallic ferromagnet with large exchange-splitting energy (Delta(exch-split)approximate to 3.0 eV) and substantial correlation effects.