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

技术概述：交换耦合磁性系统是由磁性硬相和磁性软相的混合物组成的复合磁性材料。通过在纳米尺度上整合这些相，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10nm长度尺度上的规律性来增强磁性能。本研究建议通过开发自组织纳米棋盘来实现这一目标。这种新型结构由硬磁四方相（L10）与软磁立方相（L12）在纳米尺度上交错的准周期平铺构成。在Co-Pt、Fe-Pt和Fe-Pd合金的共析成分周围，通过拟旋轴分解形成纳米棋盘状结构。该结构具有纳米级周期，有利于强交换耦合磁性，而高度的规则性将有助于对结构-性能关系的深入理解，并有望提高磁性能。这项研究将通过改变铺层周期、各个相的磁性和铺层形态来联系磁性如何随着纳米棋盘结构的改变而变化。非技术概述：磁性材料支撑着现代社会中几项极其重要的技术，包括电动机和数字数据存储。改善磁性材料的性能有很强的经济动机，例如，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，这种材料可以大大改善磁性行为。将在这里生产和研究的新材料看起来像一个棋盘，除了棋盘的正方形只有纳米宽，并且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。该研究预计将影响永磁体设计的重要领域，在该领域中，交换耦合被用来获得最大的能量存储，也将影响磁记录介质领域，在该领域中，交换耦合被用来降低高各向异性、纳米级有序相的矫顽力。除了这项研究的科学和技术影响之外，主要研究者还承诺通过培养研究生和让本科生接触研究环境，将研究和教育结合起来。此外，首席研究员指导并参与广泛的外展活动，重点是“向公众教授纳米”。磁性提供了一种高度可视化的、吸引人的方法来学习纳米尺度的行为。这些外展活动针对的是不同的人群，包括弗吉尼亚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.