Spectroscopy of molecule-based materials in high magnetic fields

技术概述：在固态和材料化学计划的支持下，本提案中概述的研究侧重于分子基材料的光学和磁光特性，其总体目标是了解物理和化学调谐对功能的影响。在前一个奖励期的关键进展的基础上，该项目集中于(i)化学简单分子磁体中的磁弹性耦合，（ii）量子自旋阶梯和有机双基的光物理性质，以及（iii）这些系统中电荷、结构和磁性之间的相互作用。在这些广泛的科学领域中，已经确定了几种可能显示出大的或广泛适用的磁光效应的模型化合物。例子包括一系列化学相关的过渡金属和混合金属氰化体系，如Mn(dca)2和Cr(Ru2)3，它们具有磁有序和量子临界跃迁，通过这些跃迁可以分析局部晶格畸变。还包括自旋阶梯，如Cu(qnx)Cl2和有机双基，如1,4-二苯二烯，其中颜色特性可以通过磁场调节。与S = 1/2卤化铜配位聚合物相比，这些材料在其行为上提供了额外的复杂性，其中最初发现了新的高场效应，但它们被很好地控制，足以作为模型系统来有意义地探索量子磁性的现象学。将这些努力结合在一起的是对耦合和功能的共同关注，这些耦合和功能来自电荷、结构和磁性之间的相互作用，以及我们用来研究这些现象的高场光谱技术。这个综合实验项目的发现将进一步补充磁性氧化物的研究，以及理论发展和设备应用。非技术概述：该计划的总体目标是研究材料在极端条件下的行为，特别是在非常高的磁场下。实现这一目标需要两个标准。首先，目标材料必须具有低能量尺度，与实验可实现的磁场相称。其次，它们必须足够柔软，能够对应用领域做出反应。分子材料符合这些标准。虽然动态测量揭示了电荷、结构和磁性之间的相互作用，并提供了对依赖于这种耦合的功能的广泛见解，但它们也赋予了对氧化物等高能量尺度材料中类似过程的理解，在这些材料中，实验可用的磁场通常不足以驱动最有趣的转变，其中一些可能对磁光器件有用。该项目利用了田纳西大学先进材料联合研究所和橡树岭国家实验室、位于塔拉哈西和洛斯阿拉莫斯的国家强磁场实验室的设施，以及与其他学术机构和国家实验室的研究人员的众多联系。同时，它支持跨学科的教育和培训，为未来在先进材料领域的学术界、政府实验室和工业界就业的不同群体的年轻人提供支持。广泛的教育、推广和服务活动也将在这个国家科学基金会资助的项目的主持下进行，特别是在会议和研讨会组织领域。

TECHNICAL SUMMARY:The research outlined in this proposal, supported by the Solid State and Materials Chemistry Program, focuses on the optical and magneto-optical properties of molecule-based materials with the overarching goal of understanding the consequences of physical and chemical tuning on functionality. Building on key advances in the previous award period, this program concentrates on (i) magnetoelastic coupling in chemically simple molecular magnets, (ii) photophysical properties of quantum spin ladders and organic biradicals, and (iii) the interplay between charge, structure, and magnetism in these systems. Within these broad scientific areas, several model compounds that may show large or widely applicable magneto-optical effects have been identified. Examples include a series of chemically-related transition metal and mixed-metal cyanide systems like Mn(dca)2 and Cr(Ru2)3 with magnetic ordering and quantum critical transitions through which local lattice distortions can be analyzed. Also included are spin ladders like Cu(qnx)Cl2 and organic biradicals such as 1,4-diphenylenenitrene, where the color properties can be tuned with magnetic field. These materials offer additional complexity in their behavior compared to the S = 1/2 copper halide coordination polymers where novel high field effects were originally discovered yet they are well-controlled enough to act as model systems to meaningfully explore the phenomenology of quantum magnetism. What brings these efforts together is a common focus on coupling and functionality deriving from the interplay between charge, structure, and magnetism and the high field spectroscopic techniques that we use to investigate these phenomena. Findings from this comprehensive experimental program will further complementary research on magnetic oxides as well as theoretical development and device applications.NON-TECHNICAL SUMMARY:The overall goal of this program is to investigate the behavior of materials under extreme conditions, specifically those of very high magnetic fields. Two criteria are required to meet this objective. First, the target materials must have low energy scales, commensurate with experimentally realizable magnetic fields. Second, they must be soft enough to respond to an applied field. Molecular materials meet these benchmarks. While dynamical measurements reveal the interplay between charge, structure, and magnetism and provide broad insight into functionalities that depend upon such coupling, they also impart understanding of similar processes in higher energy scale materials like oxides where experimentally available magnetic fields are often insufficient to drive the most interesting transitions, some of which may be useful for magneto-optical devices. This program leverages the Joint Institute of Advanced Materials at the University of Tennessee and Oak Ridge National Laboratory, the facilities at the National High Magnetic Field Laboratory in Tallahassee and Los Alamos, and numerous connections with researchers at other academic institutions and national laboratories. At the same time, it supports the interdisciplinary education and training of a diverse group of young people for future employment in academics, government laboratories, and industry in the area of advanced materials. A broad range of educational, outreach, and service activities will also take place under the auspices of this National Science Foundation funded program, especially in the area of conference and workshop organization.