The 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.
