We describe a quantitative magnetic unmixing method based on principal component
analysis (PCA) of first‐order reversal curve (FORC) diagrams. For PCA, we resample FORC
distributions on grids that capture diagnostic signatures of single‐domain (SD),
pseudosingle‐domain (PSD), and multidomain (MD) magnetite, as well as of minerals such
as hematite. Individual FORC diagrams are recast as linear combinations of end‐member
(EM) FORC diagrams, located at user‐defined positions in PCA space. The EM selection is …

Quantifying magnetic particle ensembles in rocks and sediments is a fundamental task 28 in
virtually all paleomagnetic and environmental magnetic studies. The magnetic state 29 of a
particle is highly sensitive to its size and shape, changing from superparamagnetic 30 (SP)
to stable single-domain (SD) to pseudo-single-domain (PSD) and finally to multi-31 domain
(MD) as the particle size increases from a few tens of nanometers to several tens of 32
micrometers. Rock and mineral magnetists have devised an extensive “toolbox” of mag-33 …