Collaborative Research: Magnetic Properties of Bacterial Magnetite

该项目继续并扩展了主要研究人员先前对细菌产生的单一磁域磁铁矿颗粒的磁性的研究。我们将研究时间、温度和颗粒相互作用对单个磁畴磁铁矿颗粒的影响。这些实验是及时的，因为除了先前研究的材料外，最近还获得了新的细菌磁铁矿样本。与其他合成和天然磁铁矿相比，细菌磁铁矿具有重要的优势：a)颗粒大小均匀；b)减小颗粒相互作用的影响。该项目涉及热剩余磁化、部分热剩余磁化的热退磁、粘性剩余磁化的场和温度依赖性，以及使用无滞后磁化的各种古强度方法。这两株新的产磁铁矿厌氧细菌的磁铁矿颗粒彼此之间以及与先前研究的微好氧细菌的颗粒大小和形态都有明显的不同。由于它们对沉积物的稳定剩磁具有潜在的意义，因此将对它们的磁性进行研究。特别是，这项研究将为理解静磁相互作用和粒子尺寸分布对单个磁畴粒子的时间和温度依赖关系的影响提供实验基础。

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.