Magnetic asymmetry in photoemission from Fe(100) with linearly polarized synchrotron radiation

Abstract

In an attempt to measure classical circular dichroism ͑CD͒ in the photoemission of electrons from a solid surface, valence-band photoemission from clean and adsorbate-covered chiral metal surfaces has been investigated using circularly polarized synchrotron radiation. An experimental geometry was used whereby q ជ , the polarization of the radiation, k ជ , the wave vector of the photoemitted electrons, and n ជ , the surface normal, were coplanar. It was anticipated that by doing this, so-called CDAD ͑circular dichroism in the angular distribution͒ effects associated with chiral photoemission geometries would be decoupled from classical CD arising from the difference in absorption cross-section for left and right circularly polarized light of electrons in energy states associated with R and S kinks. However, from the magnitude of the effects observed, it is evident that any classical CD features in the photoelectron spectrum arising from kinks, including photoemission from surface states or resonances, are swamped by other dichroic effects. We conclude that final-state effects in the diffraction of photoelectrons dominate the intensity of all peaks observed in angle-resolved photoemission from chiral, single crystal, metal surfaces using circularly polarized photons.

Cверхтонкие Эпитаксиальные Пленки Кобальта, Сформированные Под Графеном

“…Как известно, эффект проявляется в за-висимости формы линии фотовозбужденных линейно-поляризованным светом остовных электронов от на-правления намагниченности образца в плоскости по-верхности [15][16][17][18]. Причиной его возникновения явля-ется энергетическое расщепление возбуждаемого спин-орбитального дублета на подуровни с различными маг-нитными квантовыми числами, обусловленное взаимо-действием остовного уровня с магнито-поляризованной валентной зоной.…”

Real-space Green's function approach to angle-resolved resonant photoemission: Spin polarization and circular dichroism in itinerant magnets

“…This may be easily improved by taking layer-dependent potentials from a self-consitent surface calculation. Thereby the change of local magnetic moment at the surface due to valence bands narrowing could be taked into account [32,33,79]. While this effect is rather small in Fe(010), it might be important for other compounds and less dense surfaces.…”

“…Decay processes involving open shells, such as core-core-valence and corevalence-valence decays, are more complicated and have not been discussed in such previous works, neither the photoelectron diffraction effects. Furthermore, similarly to direct photoemission/Auger emission from magnetic surfaces, adding spin resolution to the magnetic dichroism analysis can allow to separate different contributions to the spin polarization (SP) of the outgoing electrons [32][33][34][35], but understanding the interplay between dichroism and spin polarization in autoionization channels is not straightforward.…”

High precision measurement of undulator polarization in the regime of hard x-rays

“…5,6 The range of application of brilliant x-ray beams is large and many experiments make use of the natural polarization of the undulator radiation. Angle resolved photoion measurements of molecules in gas phase, 7 experiments on surface magnetism, 8 and magnetic small angle scattering 9,10 are just a few examples in this respect. For these kind of experiments, it is important to know the exact polarization state of the undulator radiation to avoid errors in the analysis of the experimental data.…”

“…For the 3 Â 3-mm 2 slit, the polarization purity is (d 0 ¼ 2.4 6 0.2) Â 10 À4 , while the value for the 1 Â 1-mm 2 slit is (d 0 ¼ 1. 8 …”