Understanding Spin-Spin and Spin-Lattice Interactions in Molecular Nanomagnetism

了解分子纳米磁性中的自旋-自旋和自旋-晶格相互作用

• 批准号: 1610226
• 负责人: Stephen Hill
• 金额: $ 34.9万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1610226&HistoricalAwards=false
• 关键词: Understanding; Spin; Lattice; Interactions; Molecular

Non-technical Abstract:This highly interdisciplinary project involves the study of magnetic molecules whose properties can be chemically engineered at the molecular level to give desired physical properties. These so-called molecular nanomagnets provide remarkable fundamental insights into magnetism at the nanoscale, while promising important advances in information technologies. In this regard, two distinct thrusts are under investigation: the first involves the potential use of magnetic molecules as the elementary memory units (bits) in classical computers, where the information is stored in the magnetic polarization state (up or down) of the molecule; the second explores the possibility of exploiting the quantum states of such molecules to implement quantum computing algorithms. This project employs unique magnetic resonance spectroscopic techniques that have been developed by the PI at the US National High Magnetic Field Laboratory to establish structure-property relations that chemists can then use to optimally design molecules for targeted applications. Although the design criteria for classical and quantum memories (qubits) are somewhat different, at a fundamental level, they typically involve tuning/optimizing the same interactions in molecular systems. The research team is exploring how the choice of magnetic element, molecular geometry, and surrounding host material influence the stability of both classical and quantum information encoded into magnetic molecules. The team is also researching possibilities for "wiring" magnetic molecules together using organic linkers. Results obtained from the project are of interest to other research communities, including materials science, inorganic and bioinorganic chemistry. The PI is strongly committed to diversity, both in terms of student recruitment, and through active participation in the American Physical Society's Masters-to-PhD Bridge Program and National Mentoring Community.Technical Abstract:The molecular nanomagnetism field has witnessed remarkable progress during the past few years, e.g.: a four-fold increase in the temperature below which a magnetic molecule can retain its magnetization has been achieved; and the coherent manipulation and readout of a single Tb nuclear spin has been demonstrated in a molecular device. Crucial to both of these results has been a focus on simple molecules comprised of magnetic ions with strong spin-orbit anisotropy. Recent activity has seen a bifurcation into distinct thrusts: the first continues to focus on single-molecule magnets (SMMs) that can function as classical memory elements; the 2nd thrust involves the potential use of molecular nanomagnets in quantum computing applications. This project addresses both areas. Work on SMMs focuses on: (i) anisotropic spin-orbit mediated exchange involving orbitally degenerate transition metals coupled to one or two additional high-spin centers; and (ii) direct exchange between anisotropic lanthanides using spin bearing (radical) ligands. The aim in both cases is to obtain simple, yet highly anisotropic molecules (dimers and trimers), which have sufficiently large spin ground states to shut down quantum tunneling and spin-lattice relaxation pathways that prevent magnetization blocking. Meanwhile, (iii) work on spin qubits focuses on anisotropic mononuclear species in which crystal field states can be engineered that protect against dipolar spin-spin decoherence. In this situation, spin-lattice relaxation can end up limiting phase memory times. High-field/frequency electron paramagnetic resonance (EPR) and high pressures are used to gain insights into the relevant static anisotropic interactions, while pulsed EPR is employed to probe dynamical properties, including spin-spin and spin-lattice relaxation. Instruments available at the National High Magnetic Field Laboratory enable studies spanning unprecedented field and frequency ranges, opening up this powerful technique to many materials of current interest within the molecular nanomagnetism community. Strong collaboration with chemists provides a much needed feedback loop, with the potential for major advances in molecule-based magnetic materials.

非技术摘要：这个高度跨学科的项目涉及磁性分子的研究，其性质可以在分子水平上进行化学工程，以获得所需的物理性质。这些所谓的分子纳米磁体为纳米尺度的磁性提供了显著的基本见解，同时有望在信息技术方面取得重要进展。在这方面，两个不同的推力正在研究中：第一个涉及磁分子作为经典计算机中的基本存储单元（位）的潜在用途，其中信息存储在分子的磁极化状态（向上或向下）中;第二个探索利用这种分子的量子态来实现量子计算算法的可能性。该项目采用了PI在美国国家高磁场实验室开发的独特磁共振光谱技术，以建立结构-性质关系，然后化学家可以使用这些关系来优化分子的目标应用。虽然经典和量子存储器（量子比特）的设计标准有些不同，但在基本层面上，它们通常涉及调整/优化分子系统中相同的相互作用。研究小组正在探索磁性元素、分子几何形状和周围宿主材料的选择如何影响编码到磁性分子中的经典和量子信息的稳定性。该团队还在研究使用有机连接器将磁性分子“连接”在一起的可能性。从该项目获得的结果是感兴趣的其他研究社区，包括材料科学，无机和生物无机化学。PI致力于多元化，无论是在招生方面，还是通过积极参与美国物理学会的硕士到博士桥梁计划和国家指导社区。技术摘要：分子纳米磁学领域在过去几年中取得了显着的进展，例如：已经实现了磁性分子可以保持其磁化的温度的四倍增加;并且已经在分子器件中证明了单个Tb核自旋的相干操纵和读出。对这两个结果至关重要的是关注由具有强自旋轨道各向异性的磁性离子组成的简单分子。最近的活动已经分为不同的推力：第一个继续关注可以作为经典存储元件的单分子磁体（SMM）;第二个推力涉及分子纳米磁体在量子计算应用中的潜在用途。该项目涉及这两个领域。关于SMM的工作侧重于：（i）各向异性自旋-轨道介导的交换，涉及与一个或两个另外的高自旋中心偶联的轨道简并过渡金属;和（ii）使用自旋轴承（自由基）配体在各向异性镧系元素之间的直接交换。在这两种情况下的目标是获得简单但高度各向异性的分子（二聚体和三聚体），其具有足够大的自旋基态以关闭量子隧穿和自旋晶格弛豫路径，从而防止磁化阻断。与此同时，（iii）自旋量子比特的工作集中在各向异性单核物种中，可以设计晶体场状态，以防止偶极自旋-自旋退相干。在这种情况下，自旋-晶格弛豫可能最终限制相位记忆时间。高场/频率的电子顺磁共振（EPR）和高压被用来深入了解相关的静态各向异性相互作用，而脉冲EPR被用来探测动态特性，包括自旋-自旋和自旋-晶格弛豫。国家高磁场实验室提供的仪器可以进行前所未有的场和频率范围的研究，从而将这种强大的技术应用于分子纳米磁学领域的许多当前感兴趣的材料。与化学家的密切合作提供了一个急需的反馈回路，具有在分子基磁性材料方面取得重大进展的潜力。