HR: 15:15h
AN: GP33A-05 INVITED     [Abstracts]
TI: Micromagnetics and second-order reversal-curves as a route to understanding FORC diagrams of nanoparticles
AU: * Winklhofer, M
EM: michaelw@lmu.de
AF: Dept. Earth and Environm. Sci. University of Munich, Theresienstr. 41, Muenchen, 80333, Germany
AB: First-order-reversal curve (FORC) diagrams have proven useful in characterizing fine magnetic particle systems in terms of microscopic switching field distributions, characteristic interaction strengths and mean-field effects. Despite the profusion of measured FORC data, we still lack a simple, generally valid recipe for the quantitative analysis of FORC diagrams, the reason being that most samples do not act like classical linear Preisach systems, giving rise to reversible magnetization changes that tend to blur contributions from irreversible switching events. A good example illustrating the confounding influence of reversible contributions are FORC diagrams for particle systems in which vortex configurations occur as remanent states. For non-interacting Fe nanodots with well-defined grain sizes around the zero-field SD/PSD transition and random easy-axis orientation, we will show how a combination of micromagnetic modelling and second-order- reversal-curves can be used to disentangle reversible and irreversible contributions to the FORC diagram. It will also be shown that remanence-based Preisach diagrams do not fully capture the irreversible parts.
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly