Quasi-Low-Dimensional Transition Metal Compounds: Synthesis and Characterization

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The focus of this experimental program is to synthesize new materials of strongly correlated electron systems that are on the verge of electronic and structural instabilities, and to fine-tune the competing electronic interactions through the unstable region in a controlled way. Particular emphasis will be placed on the preparation of single crystal specimens to study the structural and orientation-dependent physical properties, including electrical resistivity, magnetic susceptibility, optical and X-ray absorption near-edge spectroscopies. Metal-insulator transitions associated with the onset of charge density waves/spin density waves and/or magnetic ordering; and superconductivity will be sought and characterized, and structural and physical property relationships will be stressed. Systems of interest include: (a). transition metal perovskites and Ruddlesden-Popper phases, An+1BnO3n+1 with A=rare earth and/or alkali and/or alkaline earth metal; B=Mn, Co, Fe (Mn/Fe), Ni and Ru, n=1, 2, 3; (b). niobium cluster compounds; and (c). selected novel structure types of low-dimensional ternary and quaternary transition metal chalcogenides.%%%These studies are expected to yield not only fundamental understanding and control of the properties of novel electronic/magnetic materials, but also to provide advanced materials for potential applications in microelectronics and magnetoelectronics including computers, sensors and communications. These are critical areas for maintaining US technological leadership worldwide. Moreover, the education and training of undergraduate and graduate students and postdoctoral fellows in solid state chemistry/materials science is essential to meet the technological challenges of the twenty first century.