Berlin 2012 – scientific programme
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MA: Fachverband Magnetismus
MA 16: Magnetic Particles / Clusters II
MA 16.1: Talk
Tuesday, March 27, 2012, 09:30–09:45, EB 202
Switching of single-domain magnetic particles under the influence of thermal fluctuations — •Leoni Breth1,2, Dieter Suess2, Christoph Vogler2, Bernhard Bergmair2, Markus Fuger2, Rudolf Heer1, and Hubert Brückl1 — 1AIT - Austrian Institute of Technology, Health and Environment Dept.,Vienna, Austria — 2Vienna University of Technology, Solid State Physics Dept., Vienna, Austria
The switching behavior of nanometer scale magnetic particles is of interest for various applications working at room temperature that reach from biomedicine to magnetic recording technologies. At finite temperature thermal fluctuations assist the magnetization to overcome the energy barrier separating its two stable states. The transition rate described by the Arrhenius-Néel law is exponentially decreasing with higher energy barriers. Starting from a master equation for the not-switching probability we derive a probability density function that corresponds to the switching field distribution of a single-domain particle originating solely from the presence of thermal fluctuations of the magnetization along its spatial orientation, as stated in the Néel-Brown model. Using the distribution function we are able to calculate rate-dependent coercivity and the corresponding standard deviation. Furthermore, we give mathematical arguments for the range of validity of the Néel-Brown model and we present single-spin Monte-Carlo and micromagnetic Langevin dynamics simulation data that show excellent agreement when taking into account the field-dependence of the attempt frequency in the Arrhenius-Néel law.