Simulation of Remanent, Transient, and Induced FORC Diagrams for Interacting Particles With Uniaxial, Cubic, and Hexagonal Anisotropy

The diagnostic power offirst‐order reversal curve (FORC) diagrams has recently beenenhanced by an extended measurement protocol that yields three additional FORC‐like diagrams: theremanent (remFORC), induced (iFORC), and transient (tFORC) diagrams. Here, we present micromagneticsimulations using this extended protocol, including numerical predictions of remFORC, iFORC, and tFORCsignatures for particle ensembles relevant to rock magnetism. Simulations are presented for randomlypacked single‐domain (SD) particles with uniaxial, cubic, and hexagonal anisotropy, and for chains ofuniaxial SD particles. Noninteracting particles have zero tFORC, but distinct remFORC and iFORC signals,that provide enhanced discrimination between uniaxial, cubic, and hexagonal anisotropy types. Increasinginteractions lessen the ability to discriminate between uniaxial and cubic anisotropy but reproduces achange in the pattern of positive and negative iFORC signals observed for SD‐dominated versus vortex‐dominated samples. Interactions in SD particles lead to the emergence of a bi‐lobate tFORC distribution,which is related to formation offlux‐closure in super‐vortex states. A predicted iFORC signal associated withcollapsed chains is observed in experimental data and may aid magnetofossil identification in sediments.Asymmetric FORC and FORC‐like distributions for hexagonal anisotropy are explained by the availability ofmultiple easy axes within the basal plane. A transition to uniaxial switching occurs below a critical value ofthe out‐of‐plane/in‐plane anisotropy ratio, which may allow FORC diagrams to provide insight into thestress state of hexagonal minerals, such as hematite.This work was supported financially by the National Institute of Advanced Industrial Science and Technology, Ministry of Economy, Trade and Industry, Japan (APR, HO, DH, XZ, RJH, ARM, PXH, and TS), the Australian Research Council through grant DP160100805 (APR, DH, RJH, ARM, and PXH), and by the European Research Council under the European Union's Seventh Framework Programme (FP/2007–2013)/ERC grant agreement number 320750 (RJH)