Magnetic Behavior of Nanoengineered Lithographic Particles and Arrays in the Single Domain Limit

纳米工程光刻颗粒和阵列在单畴极限下的磁性行为

• 批准号: 1063489
• 负责人: Kannan Krishnan
• 金额: $ 52.5万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1063489&HistoricalAwards=false
• 关键词: Magnetic; Behavior; Nanoengineered; Lithographic; Particles

TECHNICAL SUMMARY: The fundamental goal of this proposal is to address, for the first time, the static and dynamic magnetic behavior of metallic, nanoengineered heterostructures in the single-domain limit and in the size-range of 30-300 nm, that include shape-controlled single layers, tri-layers of synthetic anti-ferromagnets, and heterostructures with exchange-bias and exchange-spring behavior. It will emphasize size-dependent scaling laws, with studies of true nanoscale magnetic exchange phenomena by eliminating longer length-scale effects, collective behavior of large ensemble arrays and free-floating elements with complete degrees of freedom, including rotation. The central focus will be on the fundamental understanding of magnetic reversal behavior, interlayer coupling, exchange interactions, aging and memory effects and relaxation dynamics, all in the single domain limit and in the context of recent theoretical models. This new science will be enabled by high-throughput recently established nanoimprinting routines and by a series of careful and specialized magnetic measurements. Nanoimprinting allows the fabricate of identical, custom-shaped thin-film elements in the lateral size range between 30 and 300 nm over areas as large as several square centimeters---sufficient for macroscopic ensemble measurements. Unlike electron-beam lithography, with patterning times of many hours, nanoimprint lithography can pattern a whole substrate in just a few minutes. Moreover, the proposed synthesis method overcomes two principal limitations of wet-chemistry approaches, i.e. preparing monodisperse particles in this mesoscopic size range and creating heterostructured elements. Finally, the physical/magnetic microstructure at the nanometer length scale of the NLPs will be correlated at all stages with the magnetic properties measured using particle ensembles. NON-TECHNICAL SUMMARY: The properties of materials depend critically on size, especially on the nanometer length scale. Magnetic properties express this behavior most prominently. At the macroscopic scale a magnetic material breaks down into domains to minimize its magnetostatic energy. As the size of the materials is made smaller it is no longer able to sustain multiple domains and becomes a single domain material. At this length scale, it becomes possible to explore fundamental and intrinsic magnetic behavior without the interference of extrinsic characteristics arising from domain walls. It is proposed to use a novel method to synthesize large numbers of such "designer particles" that are homogeneous in size, shape, morphology and magnetic characteristics by a newly developed technique of nanoimprint lithography---a method similar to rubber-stamping but with nanoscale features. This will enable the study of the magnetic response, as well as its time dependence, of sufficiently large number of "particles" to provide statistically significant data and understanding of magnetic behavior on this length scale. This fundamental work also has potential impact on the technologies of information storage, spin electronics, magnetic logic, hard magnets for energy applications and biological sensing. The simultaneous advancement of discovery with teaching, training and learning will be integrated. These activities include developing new lecture modules for an undergraduate course in Nanotechnology and a graduate class on Magnetic Materials. A new interactive exhibit for the annual UW, College of Engineering open house will be developed; is attended by more than 4000 students from local schools. The PI plans to make the extra effort to recruit minority/women students to UW and will specifically work with Spelman College, a historical African-American liberal arts college in Atlanta, which has a joint science/engineering program in place with UW. International collaborations on electron holography with a leading group in Japan are also planned.

技术概要：该提案的基本目标是首次解决单畴极限和30-300 nm尺寸范围内的金属纳米工程异质结构的静态和动态磁行为，包括形状控制的单层，三层合成反铁磁体以及具有交换偏置和交换弹簧行为的异质结构。它将强调大小相关的比例律，通过消除较长的长度尺度效应，大型合奏阵列和自由浮动元件的集体行为，包括旋转的完整自由度，真正的纳米级磁交换现象的研究。中心重点将是对磁反转行为，层间耦合，交换相互作用，老化和记忆效应和弛豫动力学的基本理解，所有这些都在单畴极限和最近的理论模型的背景下。这项新的科学将通过最近建立的高通量纳米压印程序和一系列仔细和专门的磁性测量来实现。纳米压印允许制造相同的，定制形状的薄膜元件在横向尺寸范围在30和300纳米之间的面积大到几平方厘米-足以进行宏观整体测量。与电子束光刻不同，纳米压印光刻可以在几分钟内完成整个衬底的图案化。此外，所提出的合成方法克服了湿化学方法的两个主要局限性，即在该介观尺寸范围内制备单分散颗粒和产生异质结构元件。最后，在纳米长度尺度的NLP的物理/磁性微观结构将在所有阶段与使用粒子系综测量的磁性相关。非技术性总结：材料的性能主要取决于尺寸，特别是纳米长度尺度。磁性最突出地表达了这种行为。在宏观尺度上，磁性材料分解成畴以使其静磁能最小化。随着材料的尺寸变得更小，它不再能够维持多个域，而成为单域材料。在这个长度尺度上，可以探索基本和内在的磁性行为，而不受畴壁产生的非本征特性的干扰。建议使用一种新的方法来合成大量的这样的“设计师粒子”，是均匀的大小，形状，形态和磁特性的一种新开发的技术，纳米压印光刻-一种方法类似于橡胶冲压，但具有纳米级的功能。这将使磁响应的研究，以及它的时间依赖性，足够大的数量的“粒子”，以提供统计学上的显着数据和磁行为的理解在这个长度尺度上。这一基础性工作对信息存储技术、自旋电子学、磁逻辑、硬磁体能源应用和生物传感技术也有潜在的影响。发现与教学，培训和学习的同时推进将被整合。这些活动包括为纳米技术本科课程和磁性材料研究生课程开发新的讲座模块。将为一年一度的华盛顿大学工程学院开放日开发一个新的互动展览;来自当地学校的4000多名学生参加。PI计划做出额外的努力，招收少数民族/女学生到华盛顿大学，并将专门与斯佩尔曼学院，一个历史悠久的非裔美国人文科学院在亚特兰大，其中有一个联合科学/工程项目与华盛顿大学到位。还计划与日本的一个领导小组在电子全息术方面进行国际合作。