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