权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

High Temperature Magnetic Imaging of Titanomagnetites

钛磁铁矿的高温磁成像

基本信息

批准号：
1446998
负责人：
Bruce Moskowitz
金额：
$ 27万
依托单位：
University of Minnesota-Twin Cities
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2015
资助国家：
美国
起止时间：
2015-01-01 至 2018-12-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1446998&HistoricalAwards=false
关键词：
Temperature Magnetic Imaging Titanomagnetites

项目摘要

Naturally occurring magnetic iron oxides in the form of microscopic mineral grains are common in trace amounts in rocks, sediments, and soils as well as in archeological and extraterrestrial materials. Through various geological processes and to varying degrees of reliability, iron-oxide particles can record and store paleomagnetic information about the direction and strength of ancient planetary fields. One such process is thermomagnetic recording, whereby magnetic minerals in igneous rocks are magnetized by cooling from high temperatures to ambient surface temperatures in the presence of the geomagnetic field. Understanding the physical mechanisms for thermomagnetic recording is essential for accurate recovery of paleomagnetic information from natural materials. Yet our theoretical understanding is predicated on the simplest internal micromagnetic configurations (single-domain), appropriate for just the smallest grain sizes, and does not cover the more abundant larger grains exhibiting complex configurations (multi-domain). This research will address thermomagnetic recording in multi-domain grains by direct observations of their micromagnetic configurations, and their changes with experimentally applied fields and controlled temperatures. The research activity will improve our ability to study the fundamental physics of magnetic behavior at elevated temperatures and will improve our understanding of the magnetic behavior of common magnetic minerals. This research will benefit geoscientists investigating the origins and evolution of planetary magnetic fields on Earth and elsewhere in the solar system.Natural recording media, from which geoscientists strive to retrieve information on the ancient history of geomagnetic field, most commonly do not hold their data in well-behaved, high-fidelity magnetic mineral grains, but rather in grains with more complex micromagnetic structures. Direct high-resolution observation of the temperature-dependent micromagnetic structures in common magnetic minerals has recently become possible with the development of high-temperature magnetic force microscopes (MFM) capable of imaging magnetic patterns up to approximately 400°C. This project will focus on a detailed MFM study of the evolution of magnetization structures in grains of natural and synthetic iron oxides as functions of temperature, applied weak fields, grain size, and prior magnetic treatments. It will allow the team to study the mechanisms of natural magnetic recording, to understand their sensitivity to thermal or chemical overprinting over geologic time, and to devise optimized laboratory methods for the recovery of paleomagnetic field data from natural recording media. The research supported here will provide insight into the micromagnetic mechanisms responsible for thermoremanent magnetization and the fundamental processes that allow estimates of the paleointensity of the ancient geomagnetic field to be determined experimentally in the laboratory.

天然存在的磁性氧化铁以微观矿物颗粒的形式在岩石，沉积物和土壤以及考古和外星材料中以痕量存在。通过各种地质过程和不同程度的可靠性，氧化铁颗粒可以记录和存储有关古代行星磁场方向和强度的古地磁信息。其中一个过程是热磁记录，即火成岩中的磁性矿物通过在地磁场存在下从高温冷却到周围表面温度而被磁化。了解热磁记录的物理机制对于从天然物质中准确恢复古地磁信息至关重要。然而，我们的理论理解是基于最简单的内部微磁配置（单域），仅适用于最小的晶粒尺寸，并不包括更丰富的较大晶粒表现出复杂的配置（多域）。这项研究将解决热磁记录在多畴晶粒的微磁配置的直接观察，以及它们的变化与实验施加的磁场和控制的温度。研究活动将提高我们在高温下研究磁性行为的基础物理学的能力，并将提高我们对常见磁性矿物磁性行为的理解。这项研究将有助于地球科学家研究地球和太阳系其他地方的行星磁场的起源和演变。地球科学家努力从中检索地磁场古代历史信息的天然记录介质通常不以行为良好的高保真磁性矿物颗粒保存数据，而是以具有更复杂微磁性结构的颗粒保存数据。随着高温磁力显微镜（MFM）的发展，能够在高达约400°C的温度下对磁性图案进行成像，对常见磁性矿物中随温度变化的微磁性结构进行直接高分辨率观察最近已经成为可能。该项目将侧重于对天然和合成氧化铁颗粒中磁化结构随温度、外加弱场、粒度和先前磁处理的演变进行详细的MFM研究。它将使研究小组能够研究自然磁记录的机制，了解它们对地质时期的热或化学叠加的敏感性，并设计优化的实验室方法，用于从自然记录介质中恢复古磁场数据。在这里支持的研究将提供洞察到负责thermoreactive磁化的微磁机制和基本过程，允许估计古地磁场的古强度在实验室中实验确定。