Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 14: Surface or Interface Magnetism
O 14.4: Vortrag
Montag, 25. Februar 2008, 16:00–16:15, MA 043
Morphology and magnetism of compact 3d-metal nano-clusters on surfaces — •Violetta Sessi1, Jian Zhang1, Klaus Kuhnke1, Axel Enders2, Jan Honolka1, and Klaus Kern1 — 1Max-Planck Institut für Festkörperforschung - Stuttgart — 2Dept. of Physics and Astronomy - University of Nebraska - Lincoln
Systems of isolated 3d-metal clusters with nanometer size are known to behave as a superparamagnetic ensemble in which each cluster is a ferromagnetic entity. Only below a certain temperature (blocking temperature TB) thermal fluctuations are suppressed and cluster spins are aligned on the time scale of an experiment. Blocking can be enhanced either by increasing the surface induced magnetic anisotropy energy or by cluster-cluster interactions e.g. RKKY type interactions mediated through the substrate.
In order to study these effects we fabricated small, compact metal clusters by buffer layer assisted growth (BLAG [1]). Using this method the cluster formation takes place on a surface-supported noble gas buffer layer and the cluster growth is totally independent of the substrate.
We analyzed Co and Fe clusters supported on Ag(111) and Pt(111) by STM and by XMCD. The sample preparation using the same BLAG procedure lead to very different magnetic properties for unstrained 3D nano-clusters on Pt(111) and Ag(111) substrates, which can be attributed to the strong spin-orbit coupling of the Pt with respect to Ag. The results will be compared to ab initio calculations.
[1] J.H. Weaver, G.D. Waddill, Science 251, 1444 (1991)