This project continues and expands previous research by the principal investigators on the magnetic properties of single- magnetic-domain magnetite particles produced by bacteria. The effects of time, temperature, and particle interactions in single-magnetic-domain magnetite particles will be investigated. The experiments are timely because of the recent availability of new samples of bacterial magnetite in addition to the material studied in the previous research. Bacterial magnetite offers important advantages over other synthetic and natural magnetites; a) uniformity in particle size; and b) reduced effects of particle interactions. The project involves thermoremanent magnetization, thermal demagnetization of partial thermoremanent magnetizations, field and temperature dependence of viscous remanent magnetization, and various paleointensity methods which use anhysteretic magnetization. The magnetite particles from the two new strains of magnetite producing anaerobic bacteria have distinctly different particle sizes and morphologies from each other and from those of the previously studied microaerophilic bacteria. Their magnetic properties will be studies because of their potential significance to the stable remanence of sediments. In particular, this research will provide an experimental basis for understanding the effects of magnetostatic interactions and particle-size distributions on the time and temperature dependence of single-magnetic-domain particles.
