Magnetic Correlations and Control in Nanoscaled Molecule-based Magnets

*技术摘要*这项研究探索了氰基金属酸盐配位聚合物的电磁和结构性质之间的相互作用。特别是，异质薄膜和颗粒的制备增加了界面与体积的比率，从而允许成分之间的边界上的应力/应变效应主导性能。值得注意的是，用光照射可以对磁性进行持续的光控制，直到液氮温度，这项工作试图探索将这一特性扩展到室温的不同途径。同时，还将研究量子自旋链，重点放在S=2材料上。我们将探讨量子自旋与经典自旋在一维空间中的边界，以及局域磁环境各向异性的影响。这两个研究推进器都将使用压力作为外部参数，并且这些基于分子的磁体比传统的固态磁体更具柔韧性。物理和化学研究生直接参与研究计划的各个方面，并接受各种技术方面的独特培训，包括磁测量、X射线和中子散射以及高场、高频磁共振技术。这些工具可在研究人员的当地实验室或国家设施中获得，如国家强磁场实验室(NHMFL)、橡树岭国家实验室(ORNL)的散裂中子源(SNS)和高通量同位素反应堆(HFIR)。*新现象的发现和新设备的开发现已达到成熟水平，需要越来越复杂的材料作为纳米薄膜和粒子的组成部分。沿着这个方向，分子基磁体是一种很好的材料，因为它们的性能可以通过合成方案进行调节，并可以通过外部刺激如温度、磁场、压力/应力/应变和光照射来控制。在这项研究计划中，对历史上作为涂料颜料产生的材料进行了改性，并将其应用于纳米级薄膜和颗粒中，这些薄膜和颗粒的新颖的磁性和光学性能可以外部控制。敏感的响应是由不同成分之间的界面上产生的应力和应变造成的，需要纳米尺度来减小块体材料贡献的静态背景。这项研究试图将这种控制扩展到更高的温度和新的形态，可以提供新的磁光开关和光采集设备。各种跨学科的工具，包括磁学、电子显微镜、X射线散射和磁共振，被用来表征样品。物理和化学研究生使用最先进的仪器和数据分析技术进行培训，本科生融入工作的各个方面。归根结底，目标是增加关于环境敏感材料中磁性和电子相互作用之间相互作用的知识，这些材料的生产成本很低。

****Technical Abstract****This research explores the interplay between the electromagnetic and structural properties of cyanometallate coordination polymers. Specially, the fabrication of heterostructured films and particles increases the interface to bulk ratio, thereby allowing the stress/strain effects at the boundaries between the constituents to dominate the properties. Notably, irradiation with light allows persistent photocontrol of the magnetism up to liquid nitrogen temperatures, and this work seeks to explore different paths to extend this property to room temperature. In parallel, quantum spin chains will also be studied, and the emphasis is placed on S = 2 materials. The boundary between quantum and classical spins in one-dimension will be probed, and the influence of the anisotropy of the local magnetic environment will be explored. Both research thrusts will employ pressure as an external parameter, and these molecule-based magnets are significantly more pliable than their traditional solid-state counterparts. Physics and chemistry graduate students participate directly in every aspect of the research program and receive unique training in a variety of techniques, including magnetometry, X-ray and neutron scattering, and high-field, high-frequency magnetic resonance techniques. The tools are available in the local laboratories of the investigators or at national facilities like the National High Magnetic Field Laboratory (NHMFL), and the Spallation Neutron Source (SNS) and High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL).****Non-Technical Abstract****The discovery of novel phenomena and the development of new devices have now reached levels of maturity where increasingly complex materials are required as constituents of nanometer sized films and particles. Along this direction, molecule-based magnets are excellent materials because their properties can be tuned by synthesis protocols and controlled by external stimuli such as temperature, magnetic field, pressure/stress/strain, and irradiation by light. In this research program, materials historically generated as paint pigments are modified and employed in nanoscaled films and particles whose novel magnetic and optical properties can be externally controlled. The sensitive response results from stress and strain developed at the interface between the different constituents, and the nanometer length scales are required to diminish the static background that the bulk material contributes. The research seeks to extend this control to higher temperatures and in novel morphologies that can provide new magneto-optical switches and light harvesting devices. A variety of interdisciplinary tools, including magnetometry, electron microscopy, X-ray scattering, and magnetic resonance, are used to characterize the samples. Physics and chemistry graduate students are trained using state-of-the-art instrumentation and data analysis techniques, and undergraduate students are integrated into various aspects of the work. Ultimately, the goal is to increase the knowledge of the interplay between magnetic and electronic interactions in environmentally sensitive materials that are inexpensive to generate.