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

交换耦合磁系统是由硬磁相和软磁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提高纳米结构在10 nm长度尺度下的规则性来增强磁性能。本研究提出通过开发自组织纳米棋盘来实现这一目标。这种新颖的结构由纳米尺度上的硬磁立方相（L12）与硬磁四方相（L10）交错的准周期平铺组成。在Co-Pt、Fe-Pt和Fe-Pd合金中，共析组分周围的伪调幅分解形成纳米棋盘。该结构具有纳米级周期，有利于强交换耦合磁性，而高度的规则性将使开发人员更深入地了解结构与性能的关系，并有望提高磁性能。这项调查将相关的磁性如何演变的nanochessboard结构是通过改变平铺周期，各相的磁性，和平铺morphology.Non-Technical摘要：磁性材料的基础上的几个技术，令人难以置信的重要性，现代社会，包括电动机和数字数据存储修改。提高磁性材料的性能具有很强的经济动机，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复合磁性材料，称为“交换弹簧磁铁”，它提供了极大改善的磁性行为。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，这些材料紧密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，其中利用交换耦合来获得最大的能量存储，并且还将影响磁记录介质的领域，其中交换耦合用于降低高度各向异性的纳米级有序相的磁性。除了这项研究的科学和技术影响之外，主要研究者还坚定地承诺通过研究生的培训将研究和教育结合起来，并使本科生接触研究环境。此外，首席研究员指导并参与了广泛的外联活动，重点是“向公众教授nano”。 磁性提供了一个高度可视化，吸引人的方法来了解纳米行为。这些推广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.