Magnetic properties of tetrataenite-rich stony meteorites

概要

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Three chondrites, Yamato-74160 (LL7), ALH-77260 (L3) and St. Severin (LL6), contain considerable amount of the ordered FeNi, tetrataenite, in their metallic components. The thermomagnetic curves of these tetrataenite-rich chondrites are characterized by a very flat heating curve up to 400-450℃ and then an abrupt decrease to Curie point which ranges between 550-580℃. NRM of these chondrites contains a highly stable component which can be hardly demagnetized by alternating magnetic fields up to 1800 Oe peak. The highly stable component is identified to NRM of the tetrataenite phase which has a large magnetic and optical anisotropy. By heating up to 800℃, however, the tetrataenite phase is broken down, by the order-disorder transformation, to the ordinary disordered taenite which has a much weaker magnetic coercivity.