Understanding fine magnetic particle systems through use of first-order reversal curve diagrams

First-order reversal curve (FORC) diagrams are constructed from a class of partial magnetic hysteresis loops known as first-order reversal curves and are used to understand magnetization processes in fine magnetic particle systems. A wide-ranging literature that is pertinent to interpretation of FORC diagrams has been published in the geophysical and solid-state physics literature over the past 15 years and is summarized in this review. We discuss practicalities related to optimization of FORC measurements and important issues relating to the calculation, presentation, statistical significance, and interpretation of FORC diagrams. We also outline a framework for interpreting the magnetic behavior of magnetostatically noninteracting and interacting single domain, superparamagnetic, multidomain, single vortex, and pseudosingle domain particle systems. These types of magnetic behavior are illustrated mainly with geological examples relevant to paleomagnetism, rock magnetism, and environmental magnetism. These technical, experimental, and interpretational considerations are relevant to applications that range from improving particulate media for magnetic recording in materials science, to providing a foundation for understanding geomagnetic recording by rocks in geophysics, to interpreting depositional, microbiological, and environmental processes in sediments.Our research on FORC diagrams has been supported over the years by the U.S. National Science Foundation, the UK Natural Environment Research Council, the European Union, the Royal Society of London, and the Australian Research Council (grant DP120103952)