HR: 10:20h
AN: GP22A-01 INVITED     [Abstracts]
TI: Magnetite morphology and micromagnetic modelling: Characteristics of magnetotactic bacteria.
AU: * Williams, W
EM: Wyn.Williams@ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW United Kingdom
AU: Muxworthy, A
EM: Adrian.Muxworthy@ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW United Kingdom
AU: Ridley, P
EM: Philip.Ridley@ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW United Kingdom
AB: Bacteria have evolved a means of navigating using the earth's magnetic field by producing chains of magnetic particles that act like a compass needle. There are distinct magnetic characteristics of such chains that will optimise their efficiency as compass needles, and these will be examined in this talk. A three-dimensional finite element micromagnetic model will be used to examine different geometries of magnetite chains. The finite element approach allows modelling of much more complex magnetite geometries than can be achieved using finite difference modelling on regular grids. Furthermore, stable magnetic structures are obtained using a combination of both minimum energy and a dynamic solution of the Landau-Lifshitz-Gilbert equation. This achieves robust solutions which can follow the magnetization structure through the switching process at a constant external field. The algorithm is also capable of including thermal fluctuations in a much more rigorous way than can be obtained using minimum energy methods alone. The model will examine the role of grain geometry, magnetostatic interactions fields and domain states on the effectiveness of magnetite chains as compass needles. A comparison will be made between the most effective geometries predicted by micromagnetic modelling with those achieved by genetic optimisation in magnetosomes.
DE: 3210 Modeling
DE: 3230 Numerical solutions
DE: 1512 Environmental magnetism
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting