Berlin 2005 – scientific programme
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MA: Magnetismus
MA 24: Oberfl
ächenmagnetismus
MA 24.6: Talk
Tuesday, March 8, 2005, 11:45–12:00, TU A060
Temperature-dependent exchange splitting of image-potential states in front of a magnetic surface — •Martin Pickel1, Anke Schmidt2, Martin Wiemhöfer1, Markus Donath1, and Martin Weinelt3 — 1Physikalisches Institut, Universität Münster, Wilhelm-Klemm Str. 10, 48149 Münster — 2Lehrstuhl für Festkörperphysik, Staudtstr. 7, 91058 Erlangen — 3Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin
Electrons excited to image-potential states can be used as sensors for various surface properties. For example, an exchange-split bulk bandstructure, leads to spin-dependent binding energies of the image-potential states [1]. This allows to study magnetic properties and related electron dynamics at ferromagnetic surfaces. By spin-resolved two-photon photoemission we studied ultrathin iron films on Cu(001). The exchange splitting of the image-potential states is directly resolved for the n=1 and n=2 states. With increasing temperature the splitting is reduced and vanishes at the Curie temperature. The decrease in spin polarization with increasing temperature is found to be proportional to the splitting. The linewidths of the image-potential states are spin dependent and indicate spin-dependent lifetimes. With increasing temperature the difference in linewidth declines in accordance to the lowering of the spin-splitting. This behaviour reflects the change in the electronic structure of the Fe films. The observed collapse of the exchange splitting with temperature and the temperature behaviour of the linewidths are discussed particularly with regard to the simple Stoner picture.
[1] F. Passek and M. Donath, Phys. Rev. Lett. 69, 1101 (1992)