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Chang, Liao; Winklhofer, Michael; Roberts, Andrew P.; Dekkers, Mark J.; Horng, Chorng-Shern; Hu, Lei und Chen, Qianwang (2012): Ferromagnetic resonance characterization of greigite (Fe3S4), monoclinic pyrrhotite (Fe7S8), and non-interacting titanomagnetite (Fe3-xTixO4). In: Geochemistry Geophysics Geosystems, Vol. 13




Ferromagnetic resonance (FMR) spectroscopy has become an increasinglyuseful tool for studying the magnetic properties of natural samples.Magnetite (Fe3O4) is the only magnetic mineral that has been wellcharacterized using FMR. This limits the wider use of FMR in rockmagnetism and paleomagnetism. In this study, we applied FMR analysis toa range of magnetic minerals, including greigite (Fe3S4), monoclinicpyrrhotite (Fe7S8), magnetically non-interacting titanomagnetite(Fe3-xTixO4), and synthetic magnetite chains to constrain interpretationof FMR analysis of natural samples and to explore applications of FMRspectroscopy. We measured the FMR signatures of a wide range ofwell-characterized samples at the X-and Q-bands. FMR spectra were alsosimulated numerically to compare with experimental results. The effectsof magnetic anisotropy, mineralogy, domain state, and magnetostaticinteractions on the FMR spectra are discussed for all studied minerals.Our experimental and theoretical analyses of magneticallynon-interacting tuff samples and magnetically interacting chains enablequantitative assessment of contributions of magnetostatic interactionsand magnetic anisotropy to the FMR spectra. Our results also indicatethat intact magnetosomes are a unique system with distinct FMRsignatures. While FMR analysis is useful for characterizing magneticproperties of natural samples, care is needed when makinginterpretations because of overlaps in a range of FMR signatures ofdifferent magnetic minerals with different magnetic properties. Ouranalyses will help to constrain such interpretations in rock magneticstudies.