Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Posters: Bio/organic Molecules on Surfaces, Graphene, Solid/liquid interfaces, Metal Substrates, Electronic Structure Theory

O 36.81: Poster

Dienstag, 1. April 2014, 18:30–22:00, P1

Image-Potential States on close-packed magnetic surfaces — •Beatrice Andres, Marc Christ, Marko Wietstruk, and Martin Weinelt — Fachbereich Physik, Freie Universität Berlin, 14195 Berlin

The close-packed surfaces of ferromagnetic materials exhibit various surface states. One type are image-potential states (IPS). Located in front of the surface with a part of the probability density inside they overlap with the exchange-split bulk bands. This results in a small exchange splitting in the IPS. Due to spin conservation under laser excitation they act as excellent spin-filters in two-photon photoemission (2PPE) reflecting the spin-dependent properties of the bulk band structure.

We use spin- and time-resolved 2PPE to investigate the n=1 IPS on Gd(0001), Ni(111) and Fe(110) thin films all grown in situ on a W(110) substrate. We find the exchange splitting of the IPS scales with a factor of 3 % to that of the valence bands.

The lifetimes of electrons excited to the initially unoccupied IPS show nearly no spin dependence on Ni(111) but differ by a factor of two on Fe(110) depending on the amount of majority and minority decay channels. The temporal evolution of the spin-dependent linewidths in 2PPE serves as an indicator for quasi-elastic scattering rates which were found to be mediated by magnon emission on Fe(001) while we find no influence of magnons on Ni(111).