Solvothermal Synthesis and Characterization of Magnetic Hybrid Transition Metal-Chalcogenide Frameworks
Date
2022-08
Authors
Gamage, Eranga Hansawarni
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Kovnir, Kirill
Miller, Gordon
Vela, Javier
Zaikina, Julia
Stanley, Levi
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Abstract
Methods of tuning magnetism in tetrahedral Fe-Se frameworks have been explored by solvothermal methods. Structural and electronic rearrangements can be induced on superconducting Fe-Se frameworks by intercalation of Fe-amine coordination complexes. Even though this approach destroys superconductivity, it gives rise to interesting magnetic materials. Novel 2D layered phases with vacancies and voids with intermediate oxidation states on Fe atoms show antiferromagnetic interactions between the nearest neighbors. Chemical excision of 1D chains from 2D layers occurs during solvothermal reactions in amine solvents which transforms the oxidation state of Fe from +2 to +3. Magnetism in these chain compounds can be tuned by changing the ligand type, denticity, and steric bulk. The incorporation of charge balancing chlorides in the crystal structure results in a strong hydrogen bonding network that facilitates frustrated interchain interactions giving rise to a spinglass state. In addition, chiral As-Se pentagonal linkers can be used to convert 1D Fe-Se chains into 2D frameworks that would result in hidden magnetic ordering.
Apart from this, replacing Fe with Cr favors the formation of only 0D, 1D, and polymeric structures. These compounds could be dimeric, cubic, or double-cubane types, whose coupling between Cr centers depends on the Cr-Cr distances and bridging chalcogenide linkers. Arsenic containing Cr-Se structures can be used as building blocks to synthesize novel structures by direct ligand replacement. For Cu-Se systems, 0D compounds can be synthesized by solution-based methods at room temperature and converted to layered phases by solvothermal methods. Co also showed the possibility of forming layered Co-Se phases containing Co-amine complexes with semiconducting properties. All these compounds have been investigated for their synthesis, structure, and magnetism and are characterized by diffraction and spectroscopic methods.
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dissertation