Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 22: Magnetic Particles / Clusters II
MA 22.6: Vortrag
Mittwoch, 27. Februar 2008, 15:15–15:30, H 1028
Influence of biaxial stress on the magnetic properties of cobalt nanoparticles — •Srinivasa Saranu1, Ulf Wiedwald2, Paul Ziemann2, and Ulrich Herr1 — 1Institut für Mikro- und Nanomaterialien, Universität Ulm, 89081 Ulm — 2Institut für Festkörperphysik, Universität Ulm, 89069 Ulm
Co nanoparticles with an average diameter of 25nm have been produced using an inert gas condensation technique. The particles were deposited on Si substrates and covered in situ with a 20nm Cu film. When the substrate coverage exceeds 5 %, the remanent magnetization along the in-plane direction was larger than that along the out-of-plane direction which is attributed to the dipolar interaction between the particles. For Co particles on Ta substrates, the effect of stress on the magnetic properties of isolated particles was studied. A thin film of phospholipids (DOPC) on the Ta substrate was used to avoid the agglomeration of the particles during deposition. The lipid layer was removed in an oxygen plasma, afterwards the particles were reduced to metallic Co again using a hydrogen plasma and subsequently covered with 20nm of SiOx. The effect of stress on the magnetic properties of these particles was studied by loading the Ta substrate with hydrogen. For 0.6% of strain in the Ta substrate, out-of-plane magnetization measurements showed an increase of the saturation field Hs and a reduction of the remanent magnetization. This indicates that 25nm cobalt nanoparticles have a positive magnetostriction. Support by the Landesstiftung Baden-Wüttemberg is greatfully acknowledged.