AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS1+MC-WeA

Paper SS1+MC-WeA3
Ultrathin Fe Oxides on Cu(001): a Search for Half-Metallic Films

Wednesday, October 4, 2000, 2:40 pm, Room 208

Session: Oxide Surfaces, Interfaces and Defects
Presenter: R.H. Madjoe, Louisiana State University
Authors: R.H. Madjoe, Louisiana State University
A.N. Koveshnikov, Louisiana State University
J. Karunamuni, University of South Carolina
R.L. Stockbauer, Louisiana State University
R.L. Kurtz, Louisiana State University
Correspondent: Click to Email
Half-metallic oxides such as CrO2 and Fe3O4 may provide opportunities for new magnetic devices since their single spin orientation at the Fermi level gives rise to spin-dependent transport. However, these films are most often grown on oxide substrates which are not currently incorporated in GMR devices. We report a study of the electronic and geometric structures of Fe3O4 films grown on copper, which is currently used in commercial heterostructures. A broad array of techniques including ARUPS, NEXAFS, LEED and STM were used to characterize these films. They were grown by depositing Fe on Cu(001) at room temperature and oxidizing at 810K in 10-6 Torr O2 ambient. The particular oxide phase that forms depends on the initial Fe thickness. For Fe films less than 2 ML thick, LEED and STM measurements show that oxidation produces an FeO(111) bilayer. The oxide forms long, narrow strips with two mutually-perpendicular orientations aligned along Cu[110] and [110]. Oxidation of thicker Fe layers give crystallites of Fe3O4(111) of micron dimensions, which are oriented 15° from the [010] directions and highly lattice-matched to the Cu substrate. Both core level and valence band photoemission data will be presented. Difference spectra show that the interfaces of these films have a metallic density of states at EF, unlike any of the bulk phases of iron oxide. Near-edge x-ray absorption fine-structure (NEXAFS) at both the oxygen K- and Fe L2,3-edges will be presented in addition to magnetic linear and circularly-polarized dichroism (MLD, MCD) data. These data will be discussed in the context of the evolution of the electronic structure to that of thicker bulk-like oxide films.