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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 19.9: Poster

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

Temperature dependent magnetorelaxometry: Comparison between theory and experimental data — •Markus Schiffler, Markus Büttner, Frank Schmidl, and Paul Seidel — Friedrich-Schiller-Universität Jena, Institut für Festkörperphysik

For investigation in the properties of magnetic nanoparticles their relaxation behavior can be used. One possibility is to perform temperature dependent magnetorelaxometry (TMRX) measurements. According to the thermal activation of the particles their relaxation behavior is determined by the energy barrier distribution. For such systems there is a theory provided by [1]. The numerical simulations presented there were done with arbitrary chosen simulation parameters. On the other hand there exist extensive data records of fractionated ferrofluids. Therefore the aim of the work presented here is to simulate the energy barrier distribution for the available data. The information used in the investigation is the anisotropy constant and the particle volume concentration. The mean volume of the particles is used for rescaling the obtained energy barriers to a temperature scale comparable with measurement results. Simulations with original volume concentrations are performed and compared with original results. The influence of agglomeration and variation of the particle volume concentration provide a shift of the energy barrier distribution to lower temperatures.

[1] Berkov, D.V., Numerical calculation of the energy barrier distribution in disordered many-particle systems: the path integral method. Journal of Magnetism and Magnetic Materials, 1998. 186(1-2): p. 199-213.