Ferromagnetic Resonance of Interacting Particles: A Theoretical Study

趋磁细菌是一组分类上不同的细菌，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-缺氧界面（OAI）。磁链使细菌平行于地球磁场，并帮助它们保持在OAI附近的位置。这些链显示了自然选择的指纹，以优化每单位铁的磁矩。这是通过多种方式实现的：链中的对齐，窄尺寸范围，晶体学完美性和化学纯度。由于这些独特的特征，在细菌死亡后仍然可以识别颗粒。这种磁性化石既可以作为细菌进化的记录，也可以作为环境标志。它们可以通过显微镜最可靠地识别，但这是非常劳动密集型的。已经开发了许多磁性测量方法来快速和非侵入性地识别磁化石。然而，唯一可以明确识别链结构的测试是铁磁共振（FMR），它测量对微波频率下振荡的磁场的响应。没有理论可以预测磁性颗粒链的FMR谱。这个项目的目标是发展这样一个理论。本文的工作目标如下：1.为了计算磁小体链FMR谱上粒子相互作用的特征，2。确定链断裂和氧化对铁磁共振谱的影响。探索当前FMR方法的可能增强，和4。创建用于分析FMR光谱的资源。该项目由地球物理学和地球生物学低温地球化学计划以及网络基础设施办公室的CI再利用风险基金支持。

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.