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MA: Magnetismus

MA 8: Surface Magnetism

MA 8.6: Vortrag

Montag, 27. März 2006, 16:15–16:30, HSZ 103

Coordination effects in low-dimensional Fe-Pt alloys — •Axel Enders, Jan Honolka, Klaus Kuhnke, Violetta Sessi, Diego Repetto, and Klaus Kern — Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart

FePt alloys are in the focus of extensive research due to their remarkably large magnetic anisotropy. Our results on atomically thin FePt monolayers demonstrate that a large anisotropy is achieved also in nanostructures which do not exhibit the often-discussed L10 structure. The key for large anisotropy values rather seems to be the alloying of iron with a constituent that (i) is magnetically polarizable and (ii) exhibits large spin-orbit coupling, such as Pt. To support this we have performed XMCD measurements on Fe-Pt nanostructures with varying Fe-Fe and Fe-Pt coordination. The investigated structures include Fe impurities, Fe chains, Fe/Pt surface alloy and Fe/Pt bulk alloy on Pt substrates. As a general trend, we observe that Fe-Pt coordination stabilizes the magnetic order, while Fe-Fe coordination decreases the net magnetization significantly. The latter may be attributed to a low-spin state or even antiferromagnetism in small Fe clusters on Pt. The magnetic anisotropy and orbital magnetic moments are compared for all structures.