Detection of noninteracting single domain particles using first-order reversal curve diagrams

We present a highly sensitive and accurate method for quantitative detection and characterization of noninteracting or weakly interacting uniaxial single domain particles (UNISD) in rocks and sediments. The method is based on high-resolution measurements of first-order reversal curves (FORCs). UNISD particles have a unique FORC signature that can be used to isolate their contribution among other magnetic components. This signature has a narrow ridge along the H-c axis of the FORC diagram, called the central ridge, which is proportional to the switching field distribution of the particles. Therefore, the central ridge is directly comparable with other magnetic measurements, such as remanent magnetization curves, with the advantage of being fully selective to SD particles, rather than other magnetic components. This selectivity is unmatched by other magnetic unmixing methods, and offers useful applications ranging from characterization of SD particles for paleointensity studies to detecting magnetofossils and ultrafine authigenically precipitated minerals in sediments.