Regensburg 2010 – scientific programme
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MA: Fachverband Magnetismus
MA 33: Poster II
MA 33.36: Poster
Friday, March 26, 2010, 11:00–14:00, Poster B1
Modeling of intergrain exchange coupling for quantitative predictions of δm plots — •Volker Neu1,2, Robert Biele1,2, and Ludwig Schultz1,2 — 1IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden, Germany — 2Dresden University of Technology, Institute for Solid State Physics, D-01062 Dresden, Germany
Exchange coupling of nanocrystalline materials or interface coupling of multilayers can be studied by means of δm-plots, which compare the irreversible magnetization processes in the magnetizing branch (starting from the thermally demagnetized state) and the demagnetizing branch (starting from the fully saturated state) of a hysteresis. Assuming nanocrystalline grains with sizes well below the single domain particle size, deviations from δm=0 are attributed to either short-range intergrain exchange interactions or long-range magnetostatic interactions. While numerous experimental studies lead to qualitatively sound results, quantitative analysis on δm-plots is missing. This paper studies the effect of intergrain exchange coupling (IGEC) by looking into the fundamental magnetization process of two coupled grains by a combined numerical and analytical model. It reconstructs hysteresis and δm-plots for such coupled pairs as a function of grain size, easy axis orientation and field direction. That way, it allows predictions of the influence of grain size distributions and texture spread on the shape and absolute values of δm-curves for realistic, nanocrystalline samples. Among other findings these calculations reveal, that IGEC can lead to negative δm-results without the effect of magnetostatic interactions.