Exchange-Coupled Magnetism in Self-Organized Metallic Alloy Nanochessboard Structures

技术概述：交换耦合磁系统是由硬磁相和软磁相混合而成的复合磁性材料。通过在纳米尺度上集成这些相，可以同时获得每个相的最佳性能。一个关键的挑战是通过改善纳米结构在10 nm长度尺度上的规律性来提高磁性。这项研究建议通过开发自组织纳米棋盘来实现这一点。这种新结构由硬磁四方(L10)相和软磁立方(L12)相在纳米尺度上交错的准周期平铺组成。钴-铂、铁-铂和铁-钯合金中的纳米棋盘是在共析成分周围的伪旋节点分解形成的。该结构具有纳米尺度的周期，有利于强的交换耦合磁性，而高度的规律性将使人们能够更深入地了解结构与性能的关系，并有望提高磁性性能。这项研究将通过改变平铺周期、单个相的磁性和平铺形态来关联磁性如何随着纳米棋盘结构的改变而演变。非技术摘要：磁性材料支撑着几项对现代社会极其重要的技术，包括电机和数字数据存储。改善磁性材料的性能有着强烈的经济动机，例如，这可以减轻电机的重量或增加数据存储的密度。这项研究将利用一种新的自组织过程来形成一种被称为“交换弹簧磁铁”的复合磁性材料，这种材料的磁性行为得到了极大的改善。将在这里生产和研究的新材料看起来像一个棋盘，不同的是，棋盘的正方形只有纳米宽，由不同的磁性材料组成，这些材料密切相互作用，以提高性能。这项研究有望影响永磁体设计的重要领域，交换耦合被用来获得最大的储能，也将影响磁记录介质的领域，在磁记录介质中，交换耦合被用来降低高度各向异性的纳米有序相的矫顽力。除了这项研究的科学和技术影响之外，首席研究员还坚定地致力于通过培养研究生和让本科生接触研究环境来整合研究和教育。此外，首席调查员还指导和参与了以“向公众教授纳米技术”为重点的广泛的外联活动。磁学为了解纳米尺度的行为提供了一种非常直观、吸引人的方法。这些外展活动针对不同的人群，包括弗吉尼亚州中部服务不足地区的学校。

TECHNICAL SUMMARY: Exchange-coupled magnetic systems are composite magnetic materials consisting of a mixture of magnetically hard and soft phases. By integrating these phases at the nanoscale it is possible to obtain simultaneously the best properties of each phase. A key challenge is to enhance the magnetic properties by improving the regularity of the nanostructure at the 10 nm length scale. This research proposes to achieve this through the development of the self-organized nanochessboard. This novel structure consists of a quasi-periodic tiling of the hard magnetic tetragonal (L10) phase interleaved with a soft magnetic cubic (L12) phase on the nanometer length scale. The nanoschessboard forms by pseudospinodal decomposition around the eutectoid composition in Co-Pt, Fe-Pt and Fe-Pd alloys. The structure features a nanoscale period conducive to strong exchange-coupled magnetism, while the high degree of regularity will enable the development of a deeper understanding of the structure-property relationship, and is expected to enhance the magnetic performance. This investigation will correlate how magnetic properties evolve as the nanochessboard structure is modified by varying the tiling period, the magnetic properties of the individual phases, and the tiling morphology.NON-TECHNICAL SUMMARY: Magnetic materials underpin several technologies of incredible importance to modern society, including electric motors and digital data storage. There is strong economic motivation to improve the properties of magnetic materials, which could, for example, reduce the weight of a motor or increase the density of data storage. This research will exploit a novel self-organization process to form a composite magnetic material, known as an "exchange-spring magnet", that offers greatly improved magnetic behavior. The new material that will be produced and studied here looks like a chessboard, except that the squares of the chessboard are only nanometers across, and consist of different magnetic materials that closely interact to improve performance. The research is expected to impact the important field of permanent magnet design, where exchange coupling is exploited to obtain maximum energy storage, and will also impact the field of magnetic recording media, where exchange-coupling is used to reduce coercivity in highly anisotropic, nanoscale ordered phases. Beyond the scientific and technological impacts of this research lies a strong commitment by the principal investigator to integrate research and education through the training of graduate students, and the exposure of undergraduate students to the research environment. Furthermore, the principal investigator directs and participates in extensive outreach activities focused on "teaching nano to the public". Magnetism provides a highly visual, appealing approach to learning about nanoscale behavior. These outreach activities target a diverse population, including schools in underserved regions of central Virginia.