Spectroscopy of molecule-based materials in high magnetic fields

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TECHNICAL SUMMARY:The research outlined in this proposal, supported by the Solid State and Materials Chemistry Program, focuses on the optical and magneto-optical properties of molecule-based materials with the overarching goal of understanding the consequences of physical and chemical tuning on functionality. Building on key advances in the previous award period, this program concentrates on (i) magnetoelastic coupling in chemically simple molecular magnets, (ii) photophysical properties of quantum spin ladders and organic biradicals, and (iii) the interplay between charge, structure, and magnetism in these systems. Within these broad scientific areas, several model compounds that may show large or widely applicable magneto-optical effects have been identified. Examples include a series of chemically-related transition metal and mixed-metal cyanide systems like Mn(dca)2 and Cr(Ru2)3 with magnetic ordering and quantum critical transitions through which local lattice distortions can be analyzed. Also included are spin ladders like Cu(qnx)Cl2 and organic biradicals such as 1,4-diphenylenenitrene, where the color properties can be tuned with magnetic field. These materials offer additional complexity in their behavior compared to the S = 1/2 copper halide coordination polymers where novel high field effects were originally discovered yet they are well-controlled enough to act as model systems to meaningfully explore the phenomenology of quantum magnetism. What brings these efforts together is a common focus on coupling and functionality deriving from the interplay between charge, structure, and magnetism and the high field spectroscopic techniques that we use to investigate these phenomena. Findings from this comprehensive experimental program will further complementary research on magnetic oxides as well as theoretical development and device applications.NON-TECHNICAL SUMMARY:The overall goal of this program is to investigate the behavior of materials under extreme conditions, specifically those of very high magnetic fields. Two criteria are required to meet this objective. First, the target materials must have low energy scales, commensurate with experimentally realizable magnetic fields. Second, they must be soft enough to respond to an applied field. Molecular materials meet these benchmarks. While dynamical measurements reveal the interplay between charge, structure, and magnetism and provide broad insight into functionalities that depend upon such coupling, they also impart understanding of similar processes in higher energy scale materials like oxides where experimentally available magnetic fields are often insufficient to drive the most interesting transitions, some of which may be useful for magneto-optical devices. This program leverages the Joint Institute of Advanced Materials at the University of Tennessee and Oak Ridge National Laboratory, the facilities at the National High Magnetic Field Laboratory in Tallahassee and Los Alamos, and numerous connections with researchers at other academic institutions and national laboratories. At the same time, it supports the interdisciplinary education and training of a diverse group of young people for future employment in academics, government laboratories, and industry in the area of advanced materials. A broad range of educational, outreach, and service activities will also take place under the auspices of this National Science Foundation funded program, especially in the area of conference and workshop organization.