Exchange and spin-orbit contributions to spin-polarized LEED rotation curves of magnetic films: Fe/W(001)

Spin-polarized low-energy-electron-diffraction (SPLEED) rotation curves have been measured for 2-ML ultrathin iron films grown on a tungsten (001) substrate. This LEED technique emphasizes intraplane multiple scattering and is found to be very sensitive to the magnetism and geometry of the film. The contributions of the exchange and spin-orbit polarization, as well as the intensity asymmetry upon magnetization reversal, are shown theoretically and experimentally to be separable using symmetry-based arguments. These symmetries confer particular advantages to SPLEED rotation curves for the study of ultrathin magnetic films: they provide many independent checks of the internal consistency of the data, allow a direct evaluation of the effects of instrumental asymmetries, allow a means (symmetry averaging) for correcting for small misalignments, and permit qualitative conclusions to be drawn directly from the data. For example, the remanent axis of magnetization for Fe/W(001) is shown to be in-plane along [10]. Large magnetic asymmetries, Au, of 2% are observed for this system, showing that it is experimentally feasible to perform SPLEED with neither a spin-polarized electron source nor a polarization detector.