International Research Fellowship Program: Investigation of Structural-Magneto Correlations in a Series of Magnetic Sponges

0701068里维拉国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。 该计划的奖项提供了联合研究的机会，以及使用独特或互补的设施，专业知识和国外的实验条件。里维拉与约翰·A·里维拉博士合作。在澳大利亚新南威尔士大学大步前进。 该项目的共同支持来自数学和物理科学理事会的实验物理化学计划及其多学科活动办公室。该项目旨在利用中子散射光谱和量子力学计算全面研究一系列甲酸基磁性海绵的结构-磁相关性。 近年来，具有大的、规则的和可接近的空腔的多孔材料的开发已经看到了戏剧性的活动水平。 它们在催化、分离化学、传感器、电子学和气体储存等方面具有潜在的应用前景。 特别是磁性海绵，在未来的应用中有很大的希望。 基于金属有机骨架（MOF’s）的概念，已经合成了许多新材料，其中有机配体桥接金属阳离子。 产生具有大的开孔的系统的期望通常导致使用空间延伸的有机配体。 然而，超交换路径在分子团簇中是众所周知的，并导致在阻挫三聚体、自旋轮和单分子磁体中复杂的磁相互作用。 最近报道了一系列基于甲酸根配体（HCO 2-）的多孔骨架材料（[MII 3（HCO 2）6] M = Mn，Fe，Co，Zn），它们显示出导致铁-和铁磁相互作用的磁协同有序。 此外，据观察，在加载抗磁性物质（例如简单的烃）时，磁响应被充分改变以影响转变温度。 这些多孔的磁性材料正在使用中子散射的自旋敏感探针进行研究，包括非弹性中子散射和中子粉末衍射。 该项目有关亚铁磁性甲酸锰系统的一些早期结果的初步报告最近已被报道，并被用作研究平台。 在这项研究中，高质量的中子散射研究的低温结构的这些主机：客体系统将完成，然后详细的密度泛函理论和/或从头计算这些材料的电子和动力学性质将完成。 实验和计算之间的相关性使预测类似的系统，这是实验研究的准确性。 这项工作是一个正在进行的计划的一部分，该计划旨在交叉利用孔隙度和电子结构这两种功能，以产生显示有用的磁性和光学特性的新多孔介质，并开发这一新兴的多功能材料领域。

0701068RiveraThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a fifteen-month research fellowship by Dr. Sharon A. Rivera to work with Dr. John A. Stride at the University of New South Wales in Australia. Co-support for this project comes from the Directorate of Math and Physical Science's Experimental Physical Chemistry Program and their Office Of Multidisciplinary Activities.This project is aimed to fully study the structural-magneto correlations on a series of formate based magnetic sponges using neutron scattering spectroscopy and quantum mechanical calculations. The development of porous materials with large, regular and accessible cavities has seen a dramatic level of activity over recent years. They have potential applications in catalysis, separation chemistry, sensors, electronics and gas storage. Magnetic sponges, in particular, harness much promise for future applications. Many new materials have been synthesized upon the concept of metal-organic frameworks (MOF's), in which organic ligands bridge metallic cations. The desire to produce systems with large open pores often results in the use of spatially extended organic ligands. However, super-exchange pathways are well known in molecular clusters and lead to the complex magnetic interactions in frustrated trimers, spin-wheels and single molecule magnets. Recently a series of porous framework materials, ([MII3(HCO2)6] M = Mn, Fe, Co, Zn), based upon the formate ligand (HCO2-) have been reported that display magnetic cooperative order leading to ferri- and ferromagnetic interactions. Moreover, it was observed that upon loading with diamagnetic species (simple hydrocarbons for example), the magnetic response was sufficiently altered to affect the transition temperatures. These porous, magnetic materials are being studied using the spin-sensitive probe of neutron scattering, both inelastic neutron scattering and neutron powder diffraction. A preliminary report of some early results from this project relating to the ferrimagnetic manganese-formate system has recently been reported and is used as a platform for investigation. In this research high quality neutron scattering studies of the low temperature structures of these host:guest systems will be done, then detailed density-functional theory and/or ab initio calculations of the electronic and dynamic properties of these materials will be done. Correlations between experiment and calculation enable predictions to be made about similar systems, which are experimentally investigated for accuracy. This work forms part of an ongoing program to cross-fertilize the two functionalities of porosity and electronic structure to produce new porous media displaying useful magnetic and optical properties and to develop this emerging field of poly-functional materials.