HR: 0830h
AN: GP31B-0745    [PDF]
TI: New Observations and Theory of Single-Domain Magnetic Moments and Their Implications
AU: * Potter, D K
EM: david.potter@pet.hw.ac.uk
AF: Heriot-Watt University, Centre for Geophysical and Petrophysical Magnetism, Institute of Petroleum Engineering, Riccarton, Edinburgh, EH14 4AS United Kingdom
AU: Stephenson, A
EM: Alan.Stephenson@newcastle.ac.uk
AF: University of Newcastle Upon Tyne, Department of Physics, Newcastle Upon Tyne, NE1 7RU United Kingdom
AB: The magnetic moment of a uniaxial single-domain particle is generally assumed to be oriented in one of only two possible stable positions, either closely parallel or anti-parallel to the particle long (easy) axis. However, we demonstrate that it can actually have several quantifiable stable orientations within the same nominally uniaxial particle. A new model gives quantitative predictions verified by experiments. The results have major implications for rock magnetism, palaeomagnetism, and magnetic materials research. For instance, deflections of the natural remanence vector and computations of the ancient field vector and palaeointensity are not only controlled by the shape and distribution of the particles, but also by the possible stable orientations of the moments within single-domain particles. Furthermore, the model quantitatively accounts for several previously unexplained diverse phenomena exhibited by acicular single-domain particles, namely field-impressed anisotropies, gyroremanences, and transverse components of remanence. These phenomena are theoretically impossible in idealised uniaxial single-domain particles, and could be used to quantify the deviation from such ideal behaviour. The model may also be useful for other single-domain particle morphologies and crystal structures.
DE: 1518 Magnetic fabrics and anisotropy
DE: 1521 Paleointensity
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1527 Paleomagnetism applied to geologic processes
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting