AVS 47th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI-MoM

Paper MI-MoM1
Spin Polarized Photoemission Study of Magnetite Films: Extraction of the Bulk Polarization via a Substrate Overlayer Model

Monday, October 2, 2000, 8:20 am, Room 206

Session: Magnetic Spectroscopies
Presenter: S.A. Morton, University of Missouri, Rolla
Authors: S.A. Morton, University of Missouri, Rolla
G.D. Waddill, University of Missouri, Rolla
J.G. Tobin, Lawrence Livermore National Laboratory
S. Kim, University of California, San Diego
I.K. Schuller, University of California, San Diego
S.A. Chambers, Pacific Northwest National Laboratory
Correspondent: Click to Email
Many materials have been predicted to be half metallic, yet to date remarkably little truly compelling evidence for this behavior has emerged. One technique that can potentially yield a definitive result is spin polarized photoemission and it is from this technique that the most compelling evidence yet has emerged.@footnote 1@ However such experiments are hampered by the difficulty in producing clean stoichiometric surfaces with a polarisiation that is truly representative of that of the bulk. We have used the spin-resolved photoemission facility at the Advanced Light Source,@footnote 2@ to study the half-metallic candidate Fe@sub 3@O@sub 4@, which holds out the possibility of use in spintronic devices as a pure spin source. The epitaxial films were grown on MgO by UCD and PNNL and were characterized by RHEED, LEED, XRD, and magneto-transport measurements. We have demonstrated that cleaning the samples results in the loss of their polarization. However, our ability to perform spin resolved experiments at higher photon energies, (as a direct result of the high brightness of the 3rd generation source), has enabled us to study the near Fermi edge polarization of the samples "as received", without having to resort further to potentially destructive cleaning techniques. By measuring the polarization as a function of emission angle and photon energy, and combining these measurements with a substrate overlayer model, we have been able to extract the underlying polarization of the bulk material and have demonstrated that it is significantly higher than the 30% initially observed in the "as-received" samples, and may indeed be up to 100%. Furthermore, our spin resolved spectra demonstrate close agreement with simulated spectra derived from theoretical calculations.@footnote 3@ @FootnoteText@ @footnote 1@Park et al, Nature 392 794 (1998); Phys. Rev. Lett. 81 1953 (1998)@footnote 2@Tobin et al, MRS Symp. Proc. 524 185 (1998)@footnote 3@Zhang and Satpathy, Phys. Rev. B. 44 13319 (1991).