Experimental and Theoretical Studies of Anisotropy of Magnetic Susceptibility and Remanence

磁化率各向异性和剩磁的实验和理论研究

• 批准号: 0635699
• 负责人: Bruce Moskowitz
• 金额: $ 23.29万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-01 至 2011-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635699&HistoricalAwards=false
• 关键词: Experimental; Theoretical; Studies; Anisotropy; Magnetic

Measurable magnetic anisotropy results from a large and complex set of mechanisms and physical effects on both the grain scale and the bulk rock scale. These include: nonhydrostatic stress and magnetostriction; crystal defects and microstructures and their interactions with magnetic domain walls; reorientation of mineral grains by particulate flow, plastic deformation or other mechanisms; and magnetostatic interactions among nonuniformly-distributed ferrimagnetic particles. In our research, we are targeting particular aspects of this complex set of processes, through a combination of controlled high-temperature deformation experiments using synthetic rock analogs with prescribed compositions and particle characteristics; numerical models of the anhysteretic magnetization process for anisotropically-interacting magnetic particles; and experimental determination of the anhysteretic anisotropy of synthetic samples produced by electron-beam lithography. Specifically our experiments involve the systematic investigation into the effects of high-temperature deformation on magnetic remanence, bulk magnetic properties and magnetic anisotropy in synthetic samples containing magnetite in a matrix of calcite, fayalite, or biotite. With our experimental protocols, we are studying the interrelationships between strain, reorientation of magnetic grains, development of deformation microstructures within the magnetites, changes in bulk magnetic properties, and development of magnetic fabrics as measured by anisotropy of magnetic susceptibility and remanence. We are also investigating, using fundamental experimental and theoretical approaches, the nature of anhysteretic remanent magnetization and its anisotropy, a property that is widely measured but not very well understood. We are especially focusing on the role of interparticle magnetostatic interactions. The effects of magnetic interactions are being studied using a series of nanofabricated arrays of magnetite particles produced by electron beam lithography. The nanofabrication process allows us to produce particle arrays with controlled particle sizes, shapes, orientations and interparticle spacings. Our results of these investigations are helping us better understand the significance of magnetic fabrics in naturally-deformed rocks, in terms of deformation history and mechanisms. Broader impacts include the training and education of a graduate student and a postdoc, and the potential of this work to allow rock deformation to be characterized by magnetic anisotropy.

可测量的磁各向异性是由大量复杂的机制和对颗粒尺度和大块岩石尺度的物理效应引起的。其中包括：非流体静力应力和磁致伸缩;晶体缺陷和微观结构及其与磁畴壁的相互作用;通过颗粒流动、塑性变形或其他机制使矿物颗粒重新取向;以及非均匀分布的亚铁磁性颗粒之间的静磁相互作用。在我们的研究中，我们针对这一复杂的过程中的特定方面，通过控制高温变形实验的组合，使用合成岩石类似物与规定的成分和颗粒特性;各向异性相互作用的磁性颗粒的非滞后磁化过程的数值模型;和实验测定的非滞后各向异性的合成样品由电子束光刻。具体而言，我们的实验涉及到系统的调查高温变形的影响，剩磁，体磁性能和磁各向异性在合成样品中含有磁铁矿的基质中的方解石，铁橄榄石，或黑云母。与我们的实验方案，我们正在研究的应变，磁性晶粒的重新取向，磁铁矿内的变形微观结构的发展，在体磁性能的变化，和发展的磁性织物测量的磁化率和剩磁的各向异性之间的相互关系。我们也正在调查，使用基本的实验和理论方法，无滞后resistance磁化及其各向异性，广泛测量，但不是很好理解的属性的性质。我们特别关注粒子间静磁相互作用的作用。磁相互作用的影响正在研究使用一系列的纳米制造阵列的磁铁矿颗粒所产生的电子束光刻。纳米纤维工艺允许我们生产具有受控颗粒尺寸、形状、取向和颗粒间间距的颗粒阵列。我们的这些研究结果有助于我们更好地理解自然变形岩石中磁组构在变形历史和机制方面的意义。更广泛的影响包括研究生和博士后的培训和教育，以及这项工作的潜力，使岩石变形的特点是磁各向异性。