NSF-Europe: Correlated Phenomena in Atomically Arranged Transition Metal Perovskites

协同材料研究将开展具有原子排列局域结构的强关联体和单晶过渡金属钙钛矿相关化合物。将设计具有定制特性的新化合物，并对其性质和性质相关性进行深入研究，以展示新材料的潜在应用。在此过程中，预计将在定制材料中发现与传统超导体、磁体和介电体完全不同的新型集体现象和基态。该研究将侧重于开发新的合成工具，在大范围长度尺度上的结构，物理和化学性质的测量技术，以及根据几何约束，原子间距离和离子配位描述这些性质。通过扩大现有的欧洲合作，并开发新的合作，该项目将建立在北伊利诺伊大学材料设计实验室在复杂氧化物晶体化学方面的广泛实验能力和专业知识的基础上。新型层状RAMnMO6-？（R = La， Y, Rare Earth’s; A = Ba, Sr, Ca; M = Transition Metals）材料将被用于增强磁性和磁介电性能。重点将探讨容差因子的概念以及尺寸和电荷的差异，以可靠地描述Mn， Fe和Ni钙钛矿和RAMM'O6双钙钛矿（原子Na/ cl型有序）的热力学稳定性和结构和物理性质的预测。这些系统的策略将用于开发具有密切匹配的晶格参数和改进的磁阻、热和机械性能的新型氧化锰材料。在广泛的新型、高掺杂铜氧化物超导体中，协调材料的研究将集中在外场和压力对各向异性磁性和输运性质的影响上，以辨别导电行为的本质。Mo和Sr取代的CuBa2YCu2O7-d单晶将被生长，关键超导参数将被测量，它们的性质将与工程原子顺序相关联，最终证明化合物作为高电流导体和高磁场源的应用潜力。这项国际合作需要系统地探索组成、温度和氧含量对原子有序过渡金属钙钛矿的热力学稳定性和物理性质的影响。它将对过渡金属氧化物的多体物理、电子相关性和新基态的发生产生新的见解；它还将为定制所需属性的生产提供新的工具。该项目的影响来自于它将促进对原子尺度上物质的组织和控制的进一步了解，这将导致钙钛矿在全氧化物多功能磁/介电/电子设备中的未来应用。人们期望通过对钙钛矿晶体化学的深入了解以及合成和表征工具的进步，可以改进磁阻、介电和超导材料。该项目由材料研究部和国际办公室（西欧和波兰）共同资助，是美国国家科学基金会与欧洲材料研究合作项目（NSF 02-135）。该项目正在与法国卡昂的Crismat-ISMRA实验室合作开展，A. Maignan博士；英国剑桥大学J. Paul Attfield教授；波兰科学院物理研究所，华沙，波兰，A. Wisniewski博士；波兰科学院低温与结构研究所，弗罗茨瓦夫，波兰，K. Rogacki博士。

Collaborative materials research will be undertaken on strongly correlated bulk and single-crystal transition metal perovskite-related compounds with atomically arranged local structure. New compounds with tailored characteristics will be designed and an in-depth investigation of their properties and property correlations will be performed to demonstrate the new materials' potential applications. During this process, it is expected that novel collective phenomena and ground states, quite different from conventional superconductors, magnets, and dielectrics will be discovered in the tailored materials. The research will focus on developing new synthesis tools, measurement techniques of structural, physical, and chemical properties over a wide range of length scales, and the description of these properties in terms of geometrical constraints, interatomic distances, and ionic coordinations. By expanding existing European collaborations, and developing new ones, the project will build on the Laboratory for Materials Design at Northern Illinois University's extensive experimental capabilities and expertise in crystal chemistry of complex oxide compounds. Novel layered RAMnMO6-? (R = La, Y, Rare Earth's; A = Ba, Sr, Ca; M = Transition Metals) materials will be explored for enhanced magnetic and magneto-dielectric properties. A focused effort will explore the concepts of tolerance factor and the variances of sizes and charges to reliably describe the thermodynamic stability and prediction of structural and physical properties of perovskites of Mn, Fe, and Ni and double-perovskites (atomically Na/Cl-type ordered) of RAMM'O6. These systematic strategies will be used for developing new manganese-oxide materials with closely matched lattice parameters and improved magneto-resistive, thermal and mechanical properties. Coordinated materials research in a broad range of novel, highly overdoped copper-oxide superconductors will focus on the effects of external fields and pressures on anisotropic magnetic and transport properties to discern the nature of the conducting behavior. The Mo and Sr substituted CuBa2YCu2O7-d single-crystals will be grown, critical superconducting parameters will be measured, and their properties will be correlated to engineered atomic order to conclusively demonstrate the compounds' potential for application as high current conductors and sources of high magnetic field. This international collaboration entails the systematic exploration of the effects of composition, temperature, and oxygen content on thermodynamic stability and physical properties of atomically ordered transition metal perovskites. It will produce new insights into many-body physics of transition metal oxides, electron correlations, and the occurrence of novel ground states; it will also provide new tools for tailoring the production of desired properties. The project's impact derives from the increased understanding it will promote of the organization and control of matter on the atomic scale that will lead to future application of perovskites in all-oxide multifunctional magnetic/dielectric/electronic devices. It is expected that improved magneto-resistive, dielectric, and superconducting materials will result from the enhanced understanding of the crystal chemistry of perovskites and advancement of synthesis and characterization tools. %%%This NSF project is co-funded by the Division of Materials Research and the International Office (Western Europe and Poland) as a Cooperative Activity in Materials Research between the NSF and Europe (NSF 02-135). This project is being carried out in collaboration with the Laboratoire Crismat-ISMRA, Caen, France, Dr. A. Maignan; University of Cambridge, United Kingdom, Prof. J. Paul Attfield; Institute of Physics, Polish Academy of Sciences, Warsaw, Poland, Dr. A. Wisniewski; and Institute of Low Temperature and Structural Research, Polish Academy of Sciences, Wroclaw, Poland, Dr. K. Rogacki.