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MA: Fachverband Magnetismus

MA 19: Poster I (Bio- and Molecular Magnetism/ Magnetic Particles and Clusters/ Micro- and Nanostructured Magnetic Materials/ Magnetic Materials/ Multiferroics/ Magnetic Shape Memory Alloys/ Electron Theory of Magntism/ Spincaloric Transport/ Magnetic Coupling and Exchange Bias/ Magnetization Dynamics/ Micromagnetism and Computational Magnetics)

MA 19.11: Poster

Tuesday, March 15, 2011, 10:45–13:00, P2

Shift of the blocking temperature of Co nanoparticles by Cr capping — •Melanie Ewerlin¹, Derya Demirbas¹, Leonardo Agudo², Gunther Eggeler², and Oleg Petracic¹ — ¹Experimentalphysik IV, Ruhr-Universität Bochum, 44780 Bochum — ²Institute for Materials, Department of Materials Science, Ruhr-Universität Bochum, 44780 Bochum

We have prepared self-assembled Co nanoparticles on Al2O3 buffer layers and studied the effect of capping with various amounts of Cr onto the magnetic properties. Magnetization measurements were performed using superconducting quantum interference device (SQUID) magnetometry and structural characterization using transmission electron microscopy (TEM). The uncapped Co nanoparticles show superparamagnetic behaviour 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 0.15 nm < tCr <0.4nm the blocking temperature increases again. We suggest that for the first regime the Cr capping layer leads to an enhanced dissipation of magnetization, while the second regime is governed by inter-particle coupling via Cr bridges.