Coercivity Distributions and Magnetic Particle Interactions From First-Order Reversal Curves (FORCs): Examples from Natural Materials and Software for Data Analysis

Acton, G, Verosub, K L, Roth, A, Linderholm, D

FORC diagrams, which are constructed from multiple partial hysteresis curves, provide intriguing insights into coercivitydistributions and magnetic particle interactions in both natural and man-made materials. To facilitate the use andinterpretation of FORCs, we have written software to simplify and speed the process of constructing standard FORC diagrams,developed simple models to aid in interpreting the results, and constructed a catalog of FORC diagrams for a variety ofcommon magnetic minerals and geologic materials. The software creates a number of associated plots that illustrate themicro-susceptibility, the trajectories of FORC paths, the FORC distribution in 3-D and inside the major hysteresis loop, andthe instrumental drift during the measurement. The free software and the catalog of FORC diagrams are accessible from our web site (http://paleomag.ucdavis.edu). The FORC catalog can be used to understand how differences in a number ofvariables - the time taken in collecting each data point, the number of data collected, the filtering or smoothingused, and the signal-to-noise ratio - affect the resulting FORC diagram. The methodologies that we have developedshow how FORC diagrams can be used to characterize and quantify coercivity distributions and magnetic interactions.

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