HR: 08:20h
AN: GP31A-02    [PDF]
TI: Micromagnetic Modeling of Transient Hysteresis
AU: * Yu, Y
EM: yjyu@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive Dept 0220, La Jolla, CA 92093-0220 United States
AU: Tauxe, L
EM: ltauxe@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive Dept 0220, La Jolla, CA 92093-0220 United States
AB: Magnetic hysteresis has been used to characterize magnetic mineralogy and domain state in paleomagnetic research. Conventional hysteresis measurements have recently been extended to include transient hysteresis and first order reversing curves (FORCs). During hysteresis treatment, magnetic grains do not follow coherent reversal path as predicted by classical Stoner-Wohlfarth theory. Instead, paleomagnetically meaningful magnetic grains often experience non-uniform (known as either flower or vortex) states. In order to assess the effect of irreversible changes of partial hysteresis and the evolution of non-uniform states in hysteresis measurements, we have simulated both transient and full hysteresis in grains of magnetite for the size range 20-200 nm. Hysteresis loops were obtained for fields applied along three different crystallographic axes ([001], [100], and [111]) of magnetite for at least nine different configurations of axial ratio for each grain size. Transient hysteresis shows strong dependence on grain size, axial ratio, and the direction of applied field. In addition, we have measured transient and full hysteresis for well-defined natural and synthetic samples. Our numerical calculations and measured hysteresis provide fundamental basis in interpreting transient hysteresis and FORCs.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1521 Paleointensity
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
DE: 1599 General or miscellaneous
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting