Synthesis and Characterization of Solid-State and Molecular Quantum Magnetic Materials
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Jiang, Ningxin
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Abstract
F-element magnetic materials are crucial for the next-generation applications, such as the design of the single-molecule magnets, topological insulators, the heavy-fermion superconductors, and high-coercivity hard magnets. However, compared to first-row transition metals, f-elements have more complications including degenerate ground states and significant spin-orbit coupling. This latter phenomenon is the basis of their application in both hard magnets and in the quantum condensed matter since it induces significant magnetic anisotropy. The large ionic radii of f-elements normally lead to high coordination number and low local symmetry of f-element magnetic materials which also prevents the in-depth understanding of the physical properties of f-elements based exchange-coupled systems.
In this dissertation, the design and synthesis of novel exchanged-coupled magnetic systems were described and the impact of structural imperfection and local symmetry change on the magnetic properties of these systems were also studied. The first chapter provides an introduction to quantum spin liquid and single molecule magnet. Chapter two and three details the synthesis of two layered triangular ytterbium-based antiferromagnets. The lack of long-range magnetic ordering down to 0.1 K in both compounds was observed. Chapter four describes the synthesis and physical property studies of (CH3NH3)2NaTi3F12 with perfect kagome layer and several quantum-spin-liquid behaviors. Chapter five outlines the synthesis of (CH3NH3)2NaV3F12 which is a rare S = 1 antiferromagnet with perfect kagome layer and the magnetic characterization of this compound suggests a spin-glass state at low temperature. Chapter six details the structural and physical property studies of (CH3NH3)2KTi3F12 with slightly distorted kagome layers. Comparison between the physical properties of (CH3NH3)2KTi3F12 and (CH3NH3)2NaTi3F12 was also provided. Chapter seven outlines the development of two isomeric titanocene terbium chloride molecules. Dramatically different magnetic behaviors suggest the importance of local symmetry to the magnetic properties of small molecules. This chapter also provided a useful design strategy for the synthesis of high-performance single molecule magnets. The final chapter summarizes the research results in the thesis and provides a perspective on the design of novel solid-state and molecular magnetic materials.
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2021-12-09
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Dissertation