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O: Fachverband Oberflächenphysik

O 38: Spintronics

O 38.4: Vortrag

Dienstag, 8. März 2016, 14:45–15:00, S051

Spin-polarized electron energy loss spectrometer with detection of final state spin polarization — •Dmitry Vasilyev and Jürgen Kirschner — Max-Planck Institut für Mikrostrukturphysik, Halle, Germany

Spin polarized electron energy loss spectroscopy (SPEELS) allows to investigate Stoner excitations, as was demonstrated 30 years ago. Based on theory one should expect structured energy loss spectra with features on the scale of less than 1 eV. The spectra should change with varying the incidence angle by a few degrees, and the primary energy of electrons by less than 1 eV. However, this was not observed at that time. We have developed a new SPEELS apparatus with the detection of final state spin polarization. The new spectrometer allows us to see all the expected features. Spin-polarized electrons are generated via photoemission from GaAs-based superlattice. The direction of the electron spin can be changed by varying the light helicity. Additionally the magnetization of the target can be reversed. A multichannel spin detector is used for the measurement of the spin-polarization of the outgoing electrons. It is based on spin dependent reflection from pseudomorphic Au on Ir (001). This system provides high polarization sensitivity, up to 80%, and more that 8 months lifetime in ultrahigh vacuum. The measurement of intensity asymmetries for opposite magnetization directions allows to distinguish between spin-orbit asymmetry and exchange asymmetry. Together with detection of the spin-polarization of the outgoing electrons it allows to determine relative transition probabilities for each of the four partial intensities.