Berlin 2012 – scientific programme

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MA: Fachverband Magnetismus

MA 26: Micromagnetism / Computational Magnetics

MA 26.3: Talk

Wednesday, March 28, 2012, 11:15–11:30, H 0112

FMR in one-dimensional assemblies of magnetite nanocrystals and anisotropy evolution during growth — •Michalis Charilaou¹, Michael Winklhofer², Inés García-Rubio³, and Andreas U Gehring¹ — ¹Earth and Planetary Magnetism, Department of Earth Sciences, ETH Zurich, 8092 Zurich, Switzerland — ²Department of Earth and Environmental Science, University of Munich, 80333 Munich, Germany — ³Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland

We have simulated FMR spectra of dilute suspensions of linear magnetite chains oriented randomly in space by modeling the chain as a Stoner-Wohlfarth-type rotation ellipsoid whose long axis coincides with an easy [111] axis of the cubic magnetocrystalline anisotropy system. The validity of the model is examined by comparing the results to explicit calculations of the interactions among the particles in the chain. The single ellipsoid model reproduces the experimentally observed FMR traits of such chain assemblies and can be related to the explicit chain model by adjusting the contribution to the uniaxial anisotropy along the chain axis to account for the magnetostatic interactions. Moreover, we investigate the evolution of anisotropy in these systems by fitting FMR signals at different growth-stages of the nanoparticles.