Type of Document	Dissertation
Author	Ramsey, Chris M.
URN	etd-11102004-173554
Title	Thermo-magnetic and EPR Probing of Magnetism in Low-Dimensional Lattices and Single-Molecule Magnets
Degree	Doctor of Philosophy
Department	Chemistry and Biochemistry, Department of
Advisory Committee	Advisor Name Title Naresh Dalal Committee Chair Al Stiegman Committee Member Jim Brooks Committee Member Oliver Steinbock Committee Member
Keywords	Antiferromagnet Spin-frustration Trimer Cr(IV) Molecular Magnetism Single-molecule Magnets
Date of Defense	2004-11-02
Availability	unrestricted
Abstract This dissertation presents EPR spectroscopic, dc magnetic susceptibility, and thermo-magnetic studies of several low-dimensional transition metal systems. This work is primarily focused on the complexes Cu3(O2C16H23)6·1.2C6H12, Ru2(3,5-Cl4C13H11N2)4Cl·C6H14, [Ni(hmp)(tBuEtOH)Cl]4, and Cr(C4H13N3)(O2)2·H2O, however brief studies of Cr(NH3)3(O2)2 and [Ni0.1Zn 0.9(hmp)(tBuEtOH)Cl]4 are also included to compare with their analogs. Low-dimensional magnetic materials are of current interest due to their variability between quantum and classical magnetism. Chapter 2 describes the powder and single crystal EPR and magnetic susceptibility characterization of the 0-dimensional Cu3(O2C16H23)6·1.2C6H12 lattice. This complex is shown to be a prototypical spin-frustrated equilateral triangular system with an unusual symmetry lowering effect at very low temperature. Chapter 3 is focused on the 0-d metal-metal bonded complex Ru2(3,5-Cl4C13H11N2)4Cl·C6H14 that exhibits large zero-field splitting as measured by magnetic susceptibility on oriented single crystals, and butterfly magnetic hysteresis loops, which are analyzed in the context of a phonon bottleneck mechanism. Chapter 4 details the heat capacity characterization of the S = 4 single-molecule magnet Ni(hmp)(tBuEtOH)Cl]4 and its analog [Ni0.1Zn0.9(hmp)(tBuEtOH)Cl]4. Phase transitions for both complexes are observed and the magnetic contribution of the [Ni(hmp)(tBuEtOH)Cl]4 is calculated and compared to the experimental data in order to estimate the D-parameter. Chapter 5 presents magnetic susceptibility and heat capacity experiments as a function of temperature over 1.8-300 K and magnetic field 0-9 T on the 2-dimensional antiferromagnet Cr(C4H13N3)(O2)2·H2O and its 3-d analog Cr(NH3)3(O2)2. The ligand is shown to play a key role in the ordering processes of such systems. The results presented here should provide a significant contribution to the fundamental understanding of unique molecular magnetic phenomena.
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