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

合作材料研究将在具有原子排列的局部结构的强关联块体和单晶过渡金属钙钛矿相关化合物上进行。将设计具有定制特性的新化合物，并将对其性质和性质相关性进行深入调查，以展示新材料的潜在应用。在这一过程中，人们预计将在定制材料中发现与传统超导体、磁体和电介质截然不同的新的集体现象和基态。研究将集中于开发新的合成工具，在广泛的长度尺度上测量结构、物理和化学性质，并根据几何约束、原子间距离和离子配位来描述这些性质。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，稀土；A=Ba，Sr，Ca；M=过渡金属)材料将被用于增强磁性和磁介电性能。重点将探索容差因子和尺寸和电荷变化的概念，以可靠地描述锰、铁、镍钙钛矿和RAMM‘O6双钙钛矿(原子上Na/Cl型有序)的热力学稳定性和结构和物理性质的预测。这些系统的策略将被用于开发具有紧密匹配的晶格参数和改进的磁阻、热学和机械性能的新型锰氧化物材料。在一系列新型的、高度过度掺杂的铜氧化物超导体中进行配位材料研究，将重点放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。将生长Mo和Sr取代的CuBa2YCu2O7-d单晶，测量临界超导参数，并将其性质与工程原子有序相关联，从而最终证明该化合物作为大电流导体和强磁场源的应用潜力。这一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、电子关联和新基态的出现产生新的见解；它还将为定制所需性质的产生提供新的工具。该项目的影响来自于对它将促进在原子尺度上组织和控制物质的认识的增加，这将导致钙钛矿在全氧化物多功能磁/电/电子设备中的未来应用。随着对钙钛矿晶体化学认识的加深以及合成和表征工具的进步，有望改进磁阻材料、介电材料和超导材料。这个NSF项目是由材料研究部和国际办公室(西欧和波兰)共同资助的，作为NSF和欧洲在材料研究方面的合作活动(NSF 02-135)。该项目是与法国卡昂Crismat-ISMRA实验室A.Maignan博士、英国剑桥大学J.Paul Attfield教授、波兰华沙波兰科学院物理研究所A.Wisniewski博士以及波兰弗罗茨瓦夫波兰科学院低温与结构研究所K.Rogacki博士合作开展的。

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.