Regensburg 2013 – scientific programme

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MA: Fachverband Magnetismus

MA 36: Magnetic Measurement Techniques

MA 36.5: Talk

Thursday, March 14, 2013, 10:45–11:00, H3

The role of space charge in spin resolved photoemission experiments — •Gerard Salvatella¹, Andreas Fognini¹, Florian Sorgenfrei², Martina Dell'Angela³, Martin Beye², Florian Hieke³, Andrea Eschenlohr², Sanne de Jong⁴, Roopali Kukreja⁴, Natalia Gerasimova⁵, Joerg Raabe⁶, Christian Stamm³, Urs Ramsperger¹, Hermann Dürr⁴, Joachim Stöhr⁴, Alexander Föhlisch², Wilfried Wurth³, Andreas Vaterlaus¹, Thomas Michlmayr¹, and Yves Acremann¹ — ¹Laboratorium für Festkörperphysik, ETH Zürich, Schweiz — ²HZB Berlin, Deutschland — ³Institut für Experimentalphysik, Universität Hamburg, Deutschland — ⁴SLAC, Stanford, USA — ⁵DESY, Hamburg, Deutschland — ⁶PSI, Villigen, Schweiz

Spin resolved photoemission from a solid is one of the most direct ways of measuring the magnetization. If the whole valence band is probed the measured average spin polarization is only weakly dependent on electronic excitations of the solid and represents therefore the magnetization of the sample. Here we present an experiment where the magnetization is measured by spin resolved photoemission of the cascade electrons from a thin Iron film. The sample is exposed to the radiation of the free electron laser (FEL) FLASH in Hamburg. The measured spin polarization depends on the fluence of the FEL radiation: Higher FEL fluence reduces the measured spin polarization. Space charge simulations show the most likely cause of this effect: Space charge of the electron cloud leaving the sample selectively suppresses the emission of lower energy photoelectrons which carry the largest spin polarization.