Ferromagnetic Resonance of Interacting Particles: A Theoretical Study

相互作用粒子的铁磁共振：理论研究

• 批准号: 1015464
• 负责人: Andrew Newell
• 金额: $ 7.95万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1015464&HistoricalAwards=false
• 关键词: Ferromagnetic; Resonance; Interacting; Particles; Theoretical

Magnetotactic bacteria are a taxonomically diverse group of bacteria that have chains of ferromagnetic crystals inside. These bacteria mostly live in the oxic-anoxic interface (OAI) of aquatic environments. The magnetic chains orient the bacteria parallel to the Earth's magnetic field and help them to maintain their position near the OAI. These chains show the fingerprint of natural selection acting to optimize the magnetic moment per unit iron. This is achieved in a number of ways: the alignment in chains, a narrow size range, crystallographic perfection and chemical purity. Because of these distinctive characteristics, the particles can still be identified after the bacteria have died. Such magnetofossils are useful both as records of bacterial evolution and environmental markers. They can most reliably be identified by microscopy, but that is very labor-intensive. A number of magnetic measurements have been developed to identify magnetofossils quickly and non-invasively. However, the only test that can specifically identify the chain structure is ferromagnetic resonance (FMR), which measures the response to a magnetic field oscillating at microwave frequencies.No theory has been developed to predict the FMR spectra for chains of magnetic particles. The goal of this project is to develop such a theory. The objectives of the proposed work are as follows: 1. To calculate the signature of particle interactions on FMR spectra of magnetosome chains, 2. To determine the effects on FMR spectra of chain disruption and oxidation, 3. To explore possible enhancements of the current FMR methods, and 4. To create resources for analyzing FMR spectra.This project is supported by the Geophysics and Geobiology & Low Temperature Geochemistry Programs and the Office of Cyberinfrastructure's CI-Reuse Venture Fund.

趋磁细菌是分类学上多样化的细菌群，其内部具有铁磁晶体链。这些细菌主要生活在水生环境的缺氧界面（OAI）中。磁链使细菌与地球磁场平行，帮助它们保持在 OAI 附近的位置。这些链显示了自然选择的指纹，其作用是优化每单位铁的磁矩。这是通过多种方式实现的：链排列、窄尺寸范围、晶体学完美和化学纯度。由于这些独特的特征，细菌死亡后仍然可以识别这些颗粒。这种磁化石可用作细菌进化的记录和环境标记。通过显微镜可以最可靠地识别它们，但这非常耗费人力。已经开发出许多磁性测量方法来快速、非侵入性地识别磁化石。然而，唯一可以具体识别链结构的测试是铁磁共振 (FMR)，它测量对微波频率振荡的磁场的响应。目前还没有发展出理论来预测磁性颗粒链的 FMR 谱。该项目的目标是发展这样的理论。拟议工作的目标如下：1. 计算磁小体链 FMR 谱上粒子相互作用的特征，2. 确定链破坏和氧化对 FMR 谱的影响，3. 探索当前 FMR 方法的可能增强功能，4. 创建用于分析 FMR 谱的资源。该项目得到了地球物理学和地球生物学与低温研究所的支持 地球化学项目和网络基础设施办公室的 CI-Reuse 风险基金。