CAREER: Spectroscopic Studies of Magnetically Driven Phase Transitions in Organic & Inorganic Solids

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Abstract 9623221 Musfeldt This five-year proposal is concerned with gaining further information on magnetically driven phase transitions in low-dimensional organic and inorganic solids and expanding materials chemistry coursework at the State University of New York. In general, the low-temperature spectroscopic response of several prototypical compounds in an external magnetic field will be investigated. These compounds are well-known to display spin-density wave and spin-Peierls type phase transitions, and many other interesting physical properties. In each case, the Principal investigator and graduate students will: 1. completely characterize the optical constants of these systems using low-temperature polarized infrared and optical spectroscopies in the vicinity of the phase transition, 2. evaluate optical constants and fundamental materials parameters, such as correlation parameters and electron-molecular vibrational coupling constants, and 3. initiate magnetic field studies to probe interactions between the spin-density wave condensate (spin-density-wave type) or the lattice dynamics (spin-Peierls-type) and the spin system. At the completion of each set of experiments, the analysis will focus on spectral properties which shed light on the phase transition mechanisms and the changing nature of charge transport through the transition. Energy dissipation mechanisms will receive particular attention. Chemical structure/property considerations, a perspective which comes naturally to chemists, will also play a central role in the analysis. %%% The subject of magnetically driven phase transitions in organic molecular solids has received a great deal of attention in recent years. Despite extensive study, the conditions which govern metal - insulator transitions in low-dimensional solids are a subject of increasing controversy. Therefore, the time has come to re-examine this traditional set of materials with a new set of goals, priorities and tools. The overall goal of this research is to establish a broad program devoted to investigations of magnetically driven phase transitions in low-dimensional solids. Four specific projects are proposed that are of immediate interest to the organic and inorganic materials chemistry community. These projects will allow the Principal investigator and others to evaluate the most promising paths for further investigations in the area of magnetic materials.