AVS 46th International Symposium
    Magnetic Interfaces and Nanostructures Technical Group Tuesday Sessions
       Session MI-TuA

Paper MI-TuA1
Electronic Structure of Single Crystal CrO@sub 2@

Tuesday, October 26, 1999, 2:00 pm, Room 618/619

Session: Magnetic Spectroscopies
Presenter: C.B. Stagarescu, University of Chicago
Authors: C.B. Stagarescu, University of Chicago
X. Su, University of Chicago
D.E. Eastman, University of Chicago
K.N. Altmann, University of Wisconsin, Madison
F.J. Himpsel, University of Wisconsin, Madison
A. Gupta, IBM T.J. Watson Research Center
Correspondent: Click to Email
CrO@sub 2@ was predicted to exhibit half-metallic behavior with 100% spin polarization for electrons at the Fermi level, making it an ideal spin-injector for spin-polarized tunnelling junctions. Recently, a spin polarization of 90% at the Fermi level has been measured with a superconducting point contact.@footnote 1@ We have determined the relevant electronic states using polarization-dependent X-ray absorption (XAS) from the Cr 2p and O 1s core levels into the Cr 3d and O 2p states near the Fermi level, by X-ray magnetic dichroism (XMCD) at these edges, and by spin-polarized photoemission measurements. A clear picture emerges from the O 1s absorption edge, where a sharp peak is observed at 529.2 eV, followed by two peaks at energies of 2.1 and 3.5 eV higher. The first peak is excited only by the electric field vector (E) in the a-b plane, implying O 2p orbitals lying in that plane. It also exhibits a positive XMCD signal, which demonstrates significant hybridization of these (O 2p@sub x@, 2p@sub y@) states with the magnetic Cr 3d states of t@sub 2g@ character that produce the expected 100% majority spin polarization at the Fermi level. The two upper peaks have the opposite polarization dependence, implying an orientation of their O 2p orbitals mainly along the c axis (2X increase in magnitude from E parallel to the a axis to E perpendicular to the a axis, compared to a 10X decrease for the first peak). XMCD spectra obtained with magnetization along the easy (c) and hard (a) axis are compared. The consequences of these results for current models of the electronic structure are discussed. @FootnoteText@ @footnote 1@ R. J. Soulen et al, Science, 282, 85 (1998).