Spin and positional disorder in complex oxides

技术总结本研究计划侧重于发展对两种无序的理解：电子自旋和离子在其他完美晶体功能材料中的非相干(随机)位移。在许多磁系统中，存在自旋既不完全无序也不完全有序的温度区域。这些制度在具有强烈磁力挫折感的系统中尤其值得注意。这类体系和极性化合物之间的类比最近已经发展起来，其中由于二阶Jahn-Teller扭曲导致离子在结构中的理想位置的位移导致形成电偶极子，即使在低温下也保持无序和非相干。这些不同现象之间的联系在磁电化合物中找到了，在锥形排列中，由于自旋与原子位置上的位移耦合，在其他完全中心对称的材料中，自旋的复杂有序导致了极性的，甚至是铁电的基态。我们的目标是寻找新的氧化物系统，在其中一些无序现象可以被探索，同时，开发工具来理解它们。这些研究应该有助于更好地理解处于硬凝聚态科学前沿课题的材料，包括量子自旋液体和铁电金属，从而有助于为下一代用于电子和计算的多功能材料奠定基础。最后，拟议研究的技术开发方面将有助于形成一个不断增长的探测工具包，用于理解凝聚态物质中的结构/功能关系。对下一代材料科学家的培训将是这项工作不可或缺的一部分，他们将为未来的先进技术开发材料。这项工作得到了国家科学基金会材料研究部固体和材料化学计划的支持。非技术总结新材料的发展经常显示出有用的功能，为新技术的出现提供了基础。这项研究计划正是为了做到这一点：创造和理解结晶固体物质，展示由于材料的复杂性而出现的新行为。这个项目感兴趣的材料有望最终影响信息处理的超越-摩尔定律方法中存储和处理物质的新方法。对本科生和研究生的培训将是不可或缺的，他们需要具备思考新功能材料所需的技能，制定准备和稳定这些材料的策略，并拥有使用最先进技术来表征它们的专业知识。将设计材料的计算方法无缝地整合到实验工作中也将是一个重要的培训目标。进行拟议研究的本科生和研究生也将被纳入针对当地K-12学生的外联计划，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，其科学基础建立在建立材料组成、结构和性能之间关系的基础上。这项工作得到了国家科学基金会材料研究部固体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.