First-order reversal curve (FORC) diagrams of natural and cultured biogenic magnetic particles

Amy P. Chen*, Ramon Egli, Bruce M. Moskowitz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

53 Citations (Scopus)


First-order reversal curve (FORC) diagrams are rapidly becoming a standard tool for characterizing magnetic particles because they simultaneously incorporate information regarding magnetostatic interaction and domain states. The simplest interpretation of FORC diagrams of single-domain (SD) particles is based on the Neel interpretation of Preisach theory, which predicts that the FORC function is the product of a coercivity and an interaction field distribution. Although the underlying assumptions of this interpretation are not correct, a strictly quantitative model of weakly interacting SD grains proves that the distributions of coercivities and interaction fields can be retrieved from a FORC diagram. To test this model, we present the possibility of a quantitative interpretation of FORC diagrams, and we present measurements of samples containing magnetosomes from cultures of magnetotactic bacteria and from a lake sediment. Two samples are investigated under the electron microscope to characterize the geometrical arrangement of the particles. We find that the clustering of otherwise similar particles has a strong influence on FORC diagrams. We also obtained a crude estimate of packing densities form the FORC diagrams, which were consistent with transmission electron microscopy observations and measurements of the anhysteretic remanent magnetization.

Original languageEnglish
Article numberB08S90
Pages (from-to)1-13
Number of pages13
JournalJournal of Geophysical Research
Issue numberB8
Publication statusPublished - 4 Aug 2007
Externally publishedYes


  • FORC diagrams
  • biogenic magnetic particles
  • magnetostatic interaction


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