17:15h
AN: GP24A-06
TI: Low Temperature Magnetic Properties of Daubreelite, Troilite and Enstatite Chondrites
AU: Kosterov, A
EM: jm-andrey@kochi-u.ac.jp
AF: Center for Advanced Marine Core Research, Kochi University, Kochi, 783-8502, Japan
AU: Kosterov, A
EM: jm-andrey@kochi-u.ac.jp
AF: Institute for Rock Magnetism, University of Minnesota, Minnesota, MN 55455-0128, United States
AU: * Kohout, T
EM: tomas.kohout@helsinki.fi
AF: Division of Geophysics, University of Helsinki, Helsinki, 00014, Finland
AU: * Kohout, T
EM: tomas.kohout@helsinki.fi
AF: Department of Applied Geophysics, Charles University in Prague, Prague, 12843, Czech Republic
AU: * Kohout, T
EM: tomas.kohout@helsinki.fi
AF: Institute of Geology, Academy of Sciences of the Czech Republic, Prague, 16500, Czech Republic
AU: Jackson, M
EM: irm@umn.edu
AF: Institute for Rock Magnetism, University of Minnesota, Minnesota, MN 55455-0128, United States
AU: Kletetschka, G
EM: gunther.kletetschka@gsfc.nasa.gov
AF: Institute of Geology, Academy of Sciences of the Czech Republic, Prague, 16500, Czech Republic
AU: Kletetschka, G
EM: gunther.kletetschka@gsfc.nasa.gov
AF: Department of Physics, Catholic University of America, Washington DC, DC 20064, United States
AU: Kletetschka, G
EM: gunther.kletetschka@gsfc.nasa.gov
AF: GSFC/NASA, Code 691, Greenbelt, MD 20771, United States
AU: Lehtinen, M
EM: martti.lehtinen@
AF: Geological Museum, University of Helsinki, Helsinki, 00014, Finland
AB: Various FeNi phases are dominant magnetic phases in most chondritic meteorites. In addition, iron-bearing sulphides are present in meteorites and in cometary dust. The low-temperature magnetic properties of the daubreelite (FeCr2S4) and troilite (FeS) were investi-gated. Daubreelite is ferrimagnetic below its Curie temperature Tc = 150 - 170 K, depending on its exact chemical composition. On cooling through the Tc its saturation magnetization sharply increases up to a maximum of ~32 Am2/kg at 80 K, while the magnetic susceptibility ranges between 0.5-3.5 10 4 m3/kg reaching maximum immediately below Tc. Further cooling reveals a magnetic transition around 60 K (characterized by spin-glass-like features and cubic-to-triclinic symmetry reduction) manifesting itself in a local maximum of induced magnetization and susceptibility. Remanence acquired at 5 K shows a major drop at the transition. Troilite is antiferromagnetic at room temperature. At Tm = 62 +- 4 K we have found a magnetic transition which is likely due to spin canting. Below the transition both saturation magnetization and coercivity increase dramatically, the latter approaching 0.5 T at 5 K. Magnetic saturation is not reached in 5 T field at this temperature. However, susceptibility remains low (~4 10-7 m3/kg) with a local maximum at Tm (~1.7 10-6 m3/kg). Compared to FeNi, saturation magnetization of daubreelite at 10 K is lower by a factor of 7 and that of troilite is lower by a factor of about 200. Daubreelite can therefore contribute to or even control magnetic properties of bodies in the cold regions of Solar System. The low temperature magnetic signature of daubreelite is recognizable in magnetic measurements made on various enstatite chondrites and can thus be used to identify its presence.
DE: 1519 Magnetic mineralogy and petrology
DE: 1540 Rock and mineral magnetism
DE: 1595 Planetary magnetism: all frequencies and wavelengths
DE: 6008 Composition (1060)
DE: 6030 Magnetic fields and magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting