Physics
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufmgp22a..03g&link_type=abstract
American Geophysical Union, Fall Meeting 2003, abstract #GP22A-03
Physics
1540 Rock And Mineral Magnetism, 3924 High-Pressure Behavior, 3994 Instruments And Techniques, 5440 Magnetic Fields And Magnetism
Scientific paper
New diamond anvil cell technology now makes it possible to directly measure magnetic properties of extremely small sample volumes under high pressures. Specifically, we have developed a "non-magnetic" beryllium-copper, membrane-type diamond cell that houses a system designed to measure the reversible magnetic susceptibility of micron-sized samples under pressures in excess of 30 GPa. By placing the cell in the confines of an electromagnet, we can measure reversible susceptibility as a function of applied field, with H varying from -1.2 T to +1.2 T. Because the integral of Xrev(H)dH is proportional to the magnetic moment (of the reversible part of the remanence, or Mrev), we can measure the reversible hysteresis parameters of ferromagnetic materials as a function of pressure. We find that magnetite reversible hysteresis parameters vary little below 1.0 GPa, while at higher pressures significant increases occur in bulk coercivity (Hc) and the ratio of saturation remanent magnetization (Mrs) to saturation magnetization (Ms). The magnetic properties of magnetite are not reversible upon pressure release. Moreover, the magnetic properties of magnetite under pressure and after pressure release are highly dependent on both domain state and the presence or absence of an external magnetic field. These factors should be taken into account when studying the magnetic signatures of meteorite impacts.
Chervin J.
Gilder Stuart A.
Legoff Marc
Peyronneau Jean
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