CAS: Hard Permanent Magnets Through Molecular Design

第1部分：非技术性总结磁性是一个科学概念，它渗透到日常生活的方方面面，从电动马达的磁铁到便携式电子产品，再到用于诊断医学成像的扫描仪。在NSF材料研究部固态和材料化学计划的支持下，加州大学伯克利分校的研究人员创造了在原子水平上量身定做的新磁性材料。这项研究极大地促进了我们对永磁体材料的认识和理解，特别是如何通过分子设计原理合成永磁体材料。这项研究可能具有变革性，因为它为设计和制造与当前最先进的磁体相比具有更好性能的新磁体提供了潜在的信息。在更基本的层面上，这项研究在磁性材料、材料化学和金属有机骨架领域产生了重大影响。此外，许多从事凝聚态物理、导电材料和量子信息科学等学科的研究人员也可以从研究中获得新的见解。除了这些科学上的好处，该项目还通过为公众创造教育机会来广泛扩大其影响，特别是通过在现有合作的基础上制作教育推广计划，加州大学伯克利分校的研究生为旧金山湾区的小学生提供磁性材料课程。这一推广计划旨在接触到构成不同背景的大量K-12学生。第2部分：技术总结作为该项目的一部分，由美国国家科学基金会材料研究部的固态和材料化学计划支持，加州大学伯克利分校的研究人员测试了这一假设，即控制分子中磁各向异性的设计原则可以指导超硬永久磁材料的设计。具体地说，过去20年来，许多研究小组的工作揭示了如何将配位化学应用于以原子精度定制分子的几何和电子结构，以最大限度地提高单离子磁各向异性--永磁体强度的基本来源。该项目利用这些设计原则将选定类别的高各向异性分子--特别是高性能单分子磁体--整合到金属-有机框架材料中。过渡金属和稀土(Ln)为基础的分子结构单元主要分为四类：(I)具有巨大矫直力的混价Ln2X3核；(Ii)具有填充5d轨道的低价稀土配合物；(Iii)两配位和三配位的过渡金属配合物；以及(Iv)三角桨轮配合物。为了在这些高各向异性节点之间安装强耦合相互作用，采用了两种合成策略：(I)基于高能有机连接物的自旋和(Ii)混合价材料中的电子离域。开展这项研究的学生和博士后研究人员接受了框架材料的合成和表征方面的培训，包括复杂的物理方法，如磁测量、X射线衍射和穆斯堡尔光谱分析。此外，这些研究人员定期与伯克利和其他机构的其他研究小组的合作者互动。这种协作文化促进了一个开放和包容的科学进步论坛，并有助于相关研究人员的专业发展和团队合作技能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARYMagnetism is a scientific concept that penetrates society in myriad aspects of daily life, from the magnets in electric motors, to portable electronics, to scanners for diagnostic medical imaging. With this project, supported by the Solid State and Materials Chemistry Program in NSF’s Division of Materials Research, researchers at the University of California (UC) Berkeley create new magnetic materials whose design is tailored at the atomic level. The research significantly advances our knowledge and understanding of permanent magnet materials, in particular how to synthesize them through molecular design principles. The research could be transformative in that it offers the potential to inform the design and manufacture of new magnets with superior properties relative to the current state-of-the-art. At a more fundamental level, the research has significant impact in the areas of magnetic materials, materials chemistry, and metal–organic frameworks. In addition, many researchers engaged in the disciplines of condensed matter physics, conductive materials, and quantum information science can also benefit from the new insights gained by the research. Beyond these scientific benefits, this project broadly expand its impact by creating educational opportunities for the general public, specifically through the production of educational outreach program branching off an existing collaboration, where graduate students from UC Berkeley produce lessons on magnetic materials for Bay Area elementary school students. This outreach program is intended to reach large numbers of K-12 students that constitute diverse backgrounds.PART 2: TECHNICAL SUMMARYAs part of this project, supported by the Solid State and Materials Chemistry Program in NSF’s Division of Materials Research, researchers at UC Berkeley test the hypothesis that the design principles governing magnetic anisotropy in molecules can inform the design of ultrahard permanent magnet materials. Specifically, work from many research groups over the past two decades has uncovered how coordination chemistry can be applied to tailor geometric and electronic structures of molecules with atomic precision, to maximize the single-ion magnetic anisotropy—the fundamental source of the strength, or “hardness”, of a permanent magnet. This project employs these design principles to incorporate selected classes of high-anisotropy molecules—in particular high-performance single-molecule magnets—into metal–organic framework materials. Both transition metal- and lanthanide (Ln)-based molecular building units are pursued, falling into four main classes: (i) mixed-valence Ln2X3 cores with immense coercivity, (ii) low-valent lanthanide complexes with populated 5d orbitals, (iii) two- and three-coordinate transition metal complexes, and (iv) trigonal paddlewheel complexes. To install strong coupling interactions between these high-anisotropy nodes, two synthetic strategies are utilized: (i) high-energy organic linker-based spins and (ii) electron delocalization in mixed-valence materials. The students and postdoctoral researchers who carry out this research receive training in the synthesis of and characterization of framework materials, including sophisticated physical methods such as magnetometry, x-ray diffraction, and Mössbauer spectroscopy. Moreover, these researchers regularly interact with collaborators in other research groups, both at Berkeley and other institutions. This collaborative culture fosters an open and inclusive forum for scientific advancement, and aids in the professional development and teamwork skills of the involved researchers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.