Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 22: Surface or Interface Magnetism
O 22.1: Talk
Tuesday, March 27, 2007, 11:15–11:30, H36
Image potential states: a sensor for magnetization? — Martin Pickel1, •Markus Donath1, Anke Schmidt2, Ilja Panzer2, Fabian Giesen2, and Martin Weinelt2,3 — 1Physikalisches Institut, Universität Münster, 48149 Münster — 2Max-Born-Institut, 12489 Berlin — 3Freie Universität Berlin, Fachbereich Physik, 14195 Berlin
Image-potential surface states (IPS) at ferromagnetic surfaces exhibit exchange splittings which are explained by the exchange-split boundaries of the projected bulk band gap [1]. So far, no experimental study is available that deals with the response of this splitting to changes of the magnetization as a consequence of, e.g., temperature variation. Spin-resolved two-photon photoemission spectroscopy on the first IPS on 7 ML Fe/Cu(100) has been employed to study the influence of temperature, especially close to TC, on the spin dependence of its binding energy, spin polarization and linewidth. The evolution of the linewidths as a function of the temperature contradicts the temperature behavior of the exchange splitting and the spin polarization, both suggesting a much lower TC. This is manifested by measurements with different light polarization, which can be used to deduce the exchange splitting from spin-integrated measurements. The discrepancy is explained by domain formation below TC leading to an apparent loss of spin polarization and exchange splitting significantly below TC in the spin-resolved measurements. This experiment demonstrates the strength of using specific electronic states as sensors for magnetization, however, it shows also the danger of misinterpretation.
[1] F. Passek and M. Donath, Phys. Rev. Lett. 69, 1101 (1992)