Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 28: Surface or interface magnetism
O 28.8: Vortrag
Dienstag, 23. März 2010, 12:15–12:30, H48
Size-dependent spin structures in individual Fe nanoparticles observed by XPEEM — Arantxa Fraile Rodriguez1, Armin Kleibert1, •Joachim Bansmann2, Laura Heyderman1, and Frithjof Nolting1 — 1Paul Scherrer Institut, Villigen PSI, CH-5232 Switzerland — 2Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm
By combining x-ray magnetic circular dichroism (XMCD) with photoemission electron microscopy (PEEM), we present in situ observations of the magnetization orientation of individual Fe nanoparticles in a size range from 5 to 25 nm being in contact with a ferromagnetic Co support. Our results reveal that the magnetic moments of smaller particles (below 8 nm) are aligned parallel to the magnetic domains of the substrate while a non-collinear alignment between particles and substrate is observed for larger sizes. Numerical model calculations reproduce the experimental trend and reveal a transition from an exchange- to an anisotropy-dominated regime: the smaller particles are in a single-domain state collinearly aligned to the substrate while the larger particles exhibit a spiral-like magnetic structure determined by the magnetic anisotropy energy. These results demonstrate that the balance between the local particle-substrate interaction and the individual properties of the particles can lead to unexpected spin arrangements.