Magnetic characterization of non-ideal single-domain monoclinic pyrrhotite and its demagnetization under hydrostatic pressure up to 2 GPa with implications for impact demagnetization

Natalia S. Bezaeva, Dmitriy A. Chareev, Pierre Rochette, Myriam Kars, Jérôme Gattacceca, Joshua M. Feinberg, Ravil A. Sadykov, Dilyara M. Kuzina, Sergey N. Axenov

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Abstract

Here we present a comprehensive magnetic characterization of synthesized non-ideal single-domain (SD) monoclinic pyrrhotite (Fe7S8). The samples were in the form of a powder and a powder dispersed in epoxy. "Non-ideal" refers to a powder fraction of predominantly SD size with a minor contribution of small pseudo-single-domain grains; such non-ideal SD pyrrhotite was found to be a remanence carrier in several types of meteorites (carbonaceous chondrites, SNC. . .), which justifies the usage of synthetic compositions as analogous to natural samples. Data were collected from 5 to 633 K and include low-field magnetic susceptibility (χ0), thermomagnetic curves, major hysteresis loops, back-field remanence demagnetization curves, first-order reversal curves (FORCs), alternating field and pressure demagnetization of saturation isothermal remanent magnetization (SIRM), low temperature data (such as zero-field-cooled and field-cooled remanence datasets together with room temperature SIRM cooling-warming cycles) as well as XRD and Mössbauer spectra. The characteristic Besnus transition is observed at ∼33 K. FORC diagrams indicate interacting SD grains. The application of hydrostatic pressure up to 2 GPa using nonmagnetic high-pressure cells resulted in the demagnetization of the sample by 32-38%. Repeated cycling from 1.8 GPa to atmospheric pressure and back resulted in a total remanence decrease of 44% (after 3 cycles). Pressure demagnetization experiments have important implications for meteorite paleomagnetism and suggest that some published paleointensities of meteorites with non-ideal SD monoclinic pyrrhotite as remanence carrier may be lower limits because shock demagnetization was not accounted for.

Original languageEnglish (US)
Pages (from-to)79-90
Number of pages12
JournalPhysics of the Earth and Planetary Interiors
Volume257
DOIs
StatePublished - Aug 1 2016

Bibliographical note

Funding Information:
The work is supported by Act 211 Government of the Russian Federation , agreement No. 02.A03.21.0006 and is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University. This work was partially funded by the subsidy allocated to Kazan Federal University for the state assignment in the sphere of scientific activities. We gratefully thank colleagues from “Mossbauer optics” laboratory (Institute of Physics, Kazan Federal University) for Mössbauer measurements. We are thankful to Dmitry D. Badyukov (GEOKHI RAS), Alexei V. Sobolev (Faculty of Chemistry, M.V. Lomonosov Moscow State University) and Alexander G. Gavriliuk (Institute for Nuclear Research RAS) for helpful discussions. We are grateful to Roger Fu and an anonymous reviewer for constructive suggestions, which helped us to improve the manuscript. We are thankful to Kei Hirose for editorial handling.

Keywords

  • Magnetic properties
  • Non-ideal single-domain monoclinic pyrrhotite
  • Pressure demagnetization

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