Low-temperature Magnetism of Magnetite: Fundamental Processes and Paleomagnetic Applications

磁域成像、实验室磁测量和数值模拟研究的结合将用于研究磁铁矿的低温（120 K）相变。该活动的主要目标是在Verwey跃迁下的磁铁矿颗粒中进行微磁结构的磁成像。低温域状态将使用(1)适用于低温的干苦方法和(2)低温磁力显微镜成像。本研究的一个独特之处在于通过电子反向散射衍射分析来补充磁场成像和磁铁矿颗粒的原位晶体学取向。利用额外的晶体学信息，可以研究室温和维维跃迁以下的微磁结构中磁晶、磁弹性和静磁各向异性的相对重要性。这一研究活动将提高我们对室温下磁铁矿磁性行为的认识。此外，通过Verwey跃迁，磁畴结构在冷却或变暖期间的行为将提供对磁铁矿细颗粒（1-20微米）“永久”磁记忆机制的见解，这是过去地磁场行为的主要信息来源。最后，该项目将为理论微磁模型提供关键的实验测试，为微磁结构提供新的重要数据，并促进我们对古磁学物理基础的理解。更广泛的影响：拟议的工作将为博士后提供专业培训，设计和建造新的科学仪器，增加研究基础设施，并进一步推动地质学，物理学和微生物学合作者之间的研究伙伴关系。此外，这项研究可能会产生新的“工具”，可供其他研究人员使用，并产生适合纳入目前正在开发的岩石磁数据库的数据。

EAR-0309291Moskowitz, BruceA combination of magnetic domain imaging, laboratory magnetic measurements, and numerical modeling studies will be used to study the low-temperature (120 K) phase transition of magnetite. The major goal of the proposed activity is magnetic imaging of micromagnetic structures in magnetite particles below the Verwey transition. Low temperature domain states will be imaged using (1) a dried Bitter method adapted for cryogenic temperatures and (2) low-temperature magnetic force microscopy. A unique aspect of this study will be to complement the domain imaging with in situ crystallographic orientation of magnetite particles by electron back scatter diffraction analysis. With the additional crystallographic information, the relative importance of magnetocrystalline, magnetoelastic, and magnetostatic anisotropies to micromagnetic structures at room temperature and below the Verwey transition can be investigated.The research activity will improve our understanding of the magnetic behavior of magnetite below room temperature. Further, the behavior of magnetic domain structures during cooling or warming through the Verwey transition will provide insights into the mechanisms responsible for the "permanent" magnetic memory of fine (1-20 micrometer) particles of magnetite, the primary source of information about past geomagnetic field behavior. Finally, the project will provide critical experimental testing of theoretical micromagnetic models, provide new and important data on micromagnetic structures and advance our understanding of the physical basis of paleomagnetism.Broader Impacts: The proposed work will provide professional training of a post doctoral student, design and construct a new scientific instrument adding to research infrastructure, and the furthering of research partnerships among collaborators in geology, physics, and microbiology. Moreover, the research will likely lead to new "tools" which can be exploited by other investigators, and produce data that will be appropriate for inclusion in the rock magnetic database currently under development.