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Scalable Magnetic Anisotropy from Molecular Lanthanide Building Units

分子镧系元素构建单元的可扩展磁各向异性

基本信息

批准号：
1904937
负责人：
Jeffrey Rinehart
金额：
$ 41.81万
依托单位：
University of California-San Diego
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-08-15 至 2022-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904937&HistoricalAwards=false
关键词：
Scalable Magnetic Anisotropy Molecular Lanthanide

项目摘要

Non-technical summary:One modern approach to the design of new functional materials is through the construction and connection of molecular building units. In this approach, chemists synthesize molecules with structures that, when linked together to form a bulk material, lead to a material with specific properties. New properties can be introduced and tuned simply through modification of the molecular building unit. By analogy, a limitless number of structures can be designed starting with bricks and mortar, as opposed to one structure from a single pre-formed slab of fired clay. An area of synthesis where the building block approach remains a challenge is magnetic materials. Magnetic materials are vital components in nearly every aspect of modern life, yet only a handful of materials meet the requirements for use in applications, and none of these are made through a molecular building unit approach. The complexity of interactions that determine what direction the magnetic moment wants to align (its magnetic anisotropy) contributes to the difficulties in making the materials. As molecular building units are connected, new interactions disrupt their individual magnetic anisotropy, drastically weakening it and destroying any rational connection with the anisotropy of the original building unit. Returning to the construction analogy, connecting molecular magnets to make a bulk magnet is often akin to using bricks that spontaneously become raw clay when stacked. To change this, with support from the Solid State and Materials Chemistry program and the Chemical Structure, Dynamics and Mechanisms B program at NSF, researchers at UCSD are developing molecular building units that retain their large anisotropy values when connected to form an extended magnetic material. This class of new materials, built from individual units containing a rare earth ion, Er3+, allows the researchers to create designer magnetic structures that mimic rare and difficult-to-study motifs from solid state chemistry or create entirely new magnetic structures by design. Additionally, this project educates graduate and undergraduate students through innovative approaches such as a "In the Lab" live-feed featuring lab tours and demonstrations to enhance classroom teaching.Technical summary:A molecular building unit approach to magnetic materials can be realized only if the preferred orientation of the electron spin (its magnetic anisotropy) can be controlled. With this project, supported by the Solid State and Materials Chemistry program and the Chemical Structure, Dynamics and Mechanisms B program at NSF, molecular building blocks are identified that are capable of controlling anisotropy in the presence of the intermolecular linkages necessary to construct magnetic materials. Generating and fixing the magnetic anisotropy at the single-ion level, shifts research efforts to the rational design of complex spin geometries, enhanced magnetic coupling, and expanded dimensionality. The design principles for creating strongly anisotropic magnetism by combining a lanthanide with its specific, suitable crystal-field environment are well understood. Maintaining this anisotropy while introducing coupling interactions, however, is a complex challenge. One approach is to determine a single ligand-lanthanide combination that can direct the anisotropy roughly independent of the rest of the coordination sphere. Through computational and experimental results researchers have previously shown that the interaction between Er(III) and the cyclooctatetraenide dianion fulfills the requirements of a magnetic building unit of roughly fixed anisotropy. In this project researchers at UCSD use the molecular magnetic building unit to probe the behavior of anisotropic spins in the presence of both exchange and magnetic dipolar coupling, which enables them to construct new magnets and to independently tune system parameters, unavailable in any other class of materials. Fixing the two-site anisotropy and enhancing the exchange interaction creates stronger and switchable magnetic interactions between ions. More complex 1- to 3-dimensional spin structures that explore the limits of magnetic strength are created from these molecular building blocks. Each aspect of the system, from the coupling anisotropy and strength to the connectivity and dimensionality, allows the controlled study of an array of fundamental magnetic phenomena - often in ways that are not tunable or practical in traditional oxide or intermetallic magnetic materials. While spintronic technology has become ubiquitous, it is almost exclusively based on top-down approaches. Molecule-based materials offer the promise of enhanced tunability, terminal scalability, self-assembly, and unique quantum-confinement properties that align well with the goals of the NSF Big Ideas category: Quantum Leap.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.

非技术摘要：新型功能材料设计的一种现代方法是通过分子构建单元的构建和连接。在这种方法中，化学家合成具有结构的分子，当这些分子连接在一起形成块状材料时，会产生具有特定性质的材料。通过分子构建单元的修饰，可以简单地引入和调整新的特性。通过类比，可以从砖块和砂浆开始设计无限数量的结构，而不是从单个预成型的粘土板设计一个结构。构建块方法仍然是一个挑战的合成领域是磁性材料。磁性材料是现代生活几乎各个方面的重要组成部分，但只有少数材料满足应用要求，而且这些材料都不是通过分子构建单元方法制造的。决定磁矩想要排列的方向（磁各向异性）的相互作用的复杂性增加了材料制造的难度。当分子构建单元相互连接时，新的相互作用会破坏它们各自的磁各向异性，大大削弱它并破坏与原始构建单元的各向异性的任何合理联系。回到建筑类比，连接分子磁体来制造块状磁体通常类似于使用砖块，这些砖块在堆叠时会自发地变成原始粘土。为了改变这一点，在 NSF 固态和材料化学项目以及化学结构、动力学和机制 B 项目的支持下，加州大学圣地亚哥分校的研究人员正在开发分子构建单元，这些分子构建单元在连接形成扩展的磁性材料时保留其大的各向异性值。这类新材料由含有稀土离子 Er3+ 的单个单元构成，使研究人员能够创建设计磁性结构，模仿固态化学中罕见且难以研究的图案，或通过设计创建全新的磁性结构。此外，该项目通过创新方法对研究生和本科生进行教育，例如以实验室参观和演示为特色的“实验室内”实时直播，以加强课堂教学。技术摘要：只有当电子自旋的择优方向（其磁各向异性）可以控制时，才能实现磁性材料的分子构建单元方法。该项目得到了 NSF 固态和材料化学项目以及化学结构、动力学和机制 B 项目的支持，确定了能够在存在构建磁性材料所需的分子间键的情况下控制各向异性的分子构件。在单离子水平上产生并固定磁各向异性，将研究工作转向复杂自旋几何结构的合理设计、增强的磁耦合和扩展的维度。通过将镧系元素与其特定的、合适的晶体场环境相结合来产生强各向异性磁性的设计原理是众所周知的。然而，在引入耦合相互作用的同时保持这种各向异性是一个复杂的挑战。一种方法是确定单个配体-镧系元素组合，该组合可以大致独立于配位球的其余部分来引导各向异性。通过计算和实验结果，研究人员先前表明，Er(III) 和环辛四烯二阴离子之间的相互作用满足大致固定各向异性的磁性构建单元的要求。在这个项目中，加州大学圣地亚哥分校的研究人员使用分子磁性构建单元来探测在交换和磁偶极耦合存在下各向异性自旋的行为，这使他们能够构建新的磁体并独立调整系统参数，这是任何其他类别的材料所无法实现的。固定两位点各向异性并增强交换相互作用可以在离子之间产生更强且可切换的磁相互作用。这些分子构建块创建了更复杂的 1 至 3 维自旋结构，探索磁场强度的极限。该系统的每个方面，从耦合各向异性和强度到连通性和维度，都允许对一系列基本磁现象进行受控研究——通常以传统氧化物或金属间磁性材料中不可调谐或不实用的方式进行。虽然自旋电子技术已经变得无处不在，但它几乎完全基于自上而下的方法。分子材料有望增强可调性、终端可扩展性、自组装性和独特的量子限制特性，这些特性与 NSF 大创意类别的目标“量子飞跃”非常吻合。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。