Spin and positional disorder in complex oxides

本研究计划的重点是发展对两种无序的理解：电子自旋和离子在其他完美结晶功能材料中的非相干（随机）位移。在许多磁系统中，存在自旋既不是完全无序也不是完全有序的温度区域。这些机制在具有强磁阻挫的系统中特别显著。这种系统和极性化合物之间的类比最近已经被开发出来，其中由于二阶Jahn-Teller畸变导致离子的位置从其结构中的理想位置的位移导致形成即使在低温下也保持无序和不相干的电偶极子。在磁电化合物中发现了这些不同现象之间的联系，在磁电化合物中，由于自旋与原子位置位移的耦合，圆锥排列中自旋的复杂排序导致极性，甚至是铁电基态。我们的目标是寻找新的氧化物系统，其中一些无序现象可以探索，同时，开发工具，他们的理解。这些研究将有助于更好地理解硬凝聚态科学前沿的材料，包括量子自旋液体和铁电金属，从而有助于为下一代电子和计算多功能材料奠定基础。最后，所提出的研究的技术开发方面将有助于不断增长的工具包的探针在凝聚态物质的结构/功能关系的理解。这项工作的组成部分将是培训下一代材料科学家，他们将为未来的先进技术开发材料。这项工作得到了美国国家科学基金会材料研究部固体和材料化学计划的支持。非技术性总结显示有用功能的新材料的开发经常为新技术的出现提供基础。这项研究计划恰恰有助于这一点：创造和理解结晶固体物质，显示出由于材料的复杂性而出现的新行为。该计划感兴趣的材料预计最终将影响存储和操纵物质的新方法，超越摩尔定律处理信息的方法。该提案的组成部分将是对本科生和研究生的培训，这些学生将具备思考新功能材料所需的技能，制定制备和稳定它们的策略，并拥有使用最先进技术表征它们的专业知识。将材料设计计算方法无缝集成到实验工作中也将是一个重要的培训目标。开展拟议研究的本科生和研究生也将被纳入当地K-12学生的推广计划，重点是开发教程视频和便携式演示，强调材料研究是一个令人兴奋的研究分支，对技术进步至关重要，其科学基础是建立材料的组成，结构和性能之间的关系。这项工作得到了美国国家科学基金会材料研究部固态和材料化学计划的支持。

TECHNICAL SUMMARYThis research program focuses on developing an understanding of two kinds of disorder: of electronic spins, and of incoherent (random) displacements of ions in otherwise perfectly crystalline functional materials. In many magnetic systems, there exist temperature regimes where the spins are neither completely disordered nor fully ordered. These regimes are particularly notable in systems with strong magnetic frustration. Analogies between such systems and polar compounds have been recently developed, wherein displacements in the positions of ions from their ideal sites in the structure due to second-order Jahn-Teller distortions result in electric dipoles being formed that remain disordered and incoherent, even at low temperatures. The link between these distinct phenomena is found in magnetoelectric compounds where complex ordering of spins in conical arrangements result in polar, and even ferroelectric ground states in otherwise perfectly centrosymmetric materials, due to coupling of spins with displacements in atomic positions. The goal is to search for new oxide systems where some of these disordering phenomena can be explored, and simultaneously, to develop tools for their understanding. The investigations should lead to better understanding of materials at the forefront of topics in hard-condensed matter science, including quantum spin liquids and ferroelectric metals, and thereby help to build the foundations for the next generation of multifunctional materials for electronics and computing. Finally, the techniques development aspect of the proposed research will contribute to a growing toolkit of probes for understanding structure/function relations in condensed matter. Integral to this undertaking will be the training of the next generation of materials scientists who would develop materials for future advanced technologies. The work is supported by the Solid State and Materials Chemistry Program at National Science Foundation's Division of Materials Research.NON-TECHNICAL SUMMARYThe development of new materials displaying useful functions frequently provides the underpinnings for the emergence of new technologies. This research program contributes to precisely this: creating and understanding crystalline solid matter displaying novel behavior that emerges as a result of the complexity of the material. The materials of interest to this program are expected to eventually impact new ways of storing and manipulating matter in beyond-Moore's Law approaches to the processing of information. Integral to this proposal will be the training of undergraduate and graduate students with the skill-sets required to think of new functional materials, to develop strategies to prepare and stabilize them, and to have the expertise to characterize them using state-of-the-art techniques. The seamless integration of computational methods for materials by design into the experimental work will also be an important training goal. The undergraduate and graduate students carrying out the proposed research will also be integrated into outreach programs to local K-12 students, focusing on developing tutorial videos and portable demonstrations that emphasize materials research as an exciting branch of research that is crucial to technological advancement, and whose scientific foundations are based on establishing relations between the composition, structure, and property of materials. The work is supported by the Solid State and Materials Chemistry Program of the National Science Foundation's Division of Materials Research.