Crystal Growth, Structural Characterization and Spin Models of Cobalt-Compounds

This body of work explores the growth and structure of two different cobalt containing compounds that may show interesting quantum spin behaviors: [(CH3)3NH]CoCl3 and BaCo2(PO4)2. In [(CH3)3NH]CoCl3, the Co ions are arranged in a chain and show anti-ferromagnetic interactions, making this system a good approximation for a one-dimensional Ising model. In BaCo2(PO4)2 ,the Co ions are arranged on a honeycomb lattice, with geometrical frustration of the magnetic interactions. The crystal growth and room temperature single crystal structure of the linear magnetic chain compound [(CH3)3NH]CoCl3 is reported, along with low temperature magnetic susceptibility and heat capacity measurements. [(CH3)3NH]CoCl3 single crystals were grown using two methods: slow evaporation and seeded growth. The compound crystallizes in an orthorhombic structure with lattice parameters a =7.2716 (3) Å b =8.0983(3) Å and c =16.6473(5) Å, consistent with literature values. Seeded crystal growth in a supersaturated solution resulted in large crystals with well-developed habit. [(CH3)3NH]CoCl3 is of interest because it realizes a one-dimensional (1-D) spin system, which can be probed through heat capacity and magnetic susceptibility measurements. Attempts to grow deuterated crystals for neutron scattering experiments are in progress. A literature review and experimental analysis on the synthesis of BaCo2(PO4)2 is also reported. Single crystals of BaCo2(PO4)2 were previously grown using hydrothermal methods. Although no single crystals of Barium Cobalt Phosphate have been obtained so far, several side products resulting from different reactants, pH, and temperatures profiles have been isolated. The main goal, to obtain the single crystal of BaCo2(PO4)2 to probe the spin interactions has not yet been attained.