Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 20: Poster I - Biomagnetism, FePt Nanoparticles, Magnetic Particles/Clusters, Magnetic Materials, Magnetic Semiconductors, Half-metals/Oxides, Multiferroics, Topological Insulators, Spin structures/Phase transitions, Electron theory/Computational micromagnetics, Magnetic coupling phenomena/Exchange bias, Spin-dependent transport, Spin injection/spin currents, Magnetization/Demagnetization dynamics, Magnetic measurement techniques
MA 20.7: Poster
Dienstag, 27. März 2012, 12:15–15:15, Poster A
Shift of the blocking temperature of Co nanoparticles by Cr capping — •Melanie Ewerlin1, Derya Demirbas1, Leonardo Agudo2, Gunther Eggeler2, and Oleg Petracic1 — 1Institut für Experimentalphysik / Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany — 2Institute for Materials, Department of Material Science, Ruhr-Universität Bochum, 44780 Bochum, Germany
We have prepared Co nanoparticles (NPs) on Al2O3 buffer layers and studied the effect of capping with various amounts of Cr onto the magnetic properties. Structural and magnetometric characterization was performed using TEM and SQUID magnetometry, respectively. The uncapped Co NPs show superparamagnetic behavior with a blocking temperature of TB=14K. The magnetic properties are strongly influenced by the Cr capping resulting in a decrease of TB for nominal thicknesses of Cr up to 0.15nm. However, for larger values the blocking temperature increases again. XMCD measurements at the Cr edge indicate an anti-parallel alignment of the magnetic moments in the Cr layer with respect to the moments in the Co particle, which leads to a decrease of the effective magnetic volume and hence to a decrease of TB. The second regime is governed by inter-particle coupling via Cr-bridges.