Please use this identifier to cite or link to this item: http://arks.princeton.edu/ark:/88435/dsp01x059c980w
 Title: STRUCTURAL AND MAGNETIC PROPERTIES OF IRIDIUM AND NIOBIUM PYROCHLORE OXIDES Authors: Ribet, Stephanie Megan Advisors: Cava, Robert J. Department: Chemistry Class Year: 2016 Abstract: This thesis has two major components: a study of Bi$$_{2-x}$$Co$$_{x}$$Ir$$_{2}$$O$$_{7}$$ and a study of Ca$$_{2}$$Nb$$_{2}$$O$$_{6}$$F. Solid oxide compounds with the pyrochlore structure (A2B2O7) are known for interesting and occasionally dramatic magnetic and electric properties due to the motif of corner-sharing tetrahedra that they can contain. Iridium is a very large element with relativistic effects, such as spin-orbit coupling. This thesis reports the metallic series Bi$$_{2-x}$$Co$$_{x}$$Ir$$_{2}$$O$$_{7}$$ (x=0.5, 0.42, 0.35, 0.25, 0.1, 0). Existing structures predict that cobalt should substitute on the iridium site, but here cobalt substituted on the bismuth site. Bi$$_{2}$$Ir$$_{2}$$O$$_{7}$$ was diamagnetic, and the cobalt doped compounds were paramagnetic. At the highest cobalt content (x=0.5, 0.42, 0.35), the compounds ordered as a spin glass, as shown by magnetic susceptibility data. Niobium strongly prefers a +5 oxidation state, but when it does change its electron count, it is known to have interesting magnetic properties. The chemical formula of Ca$$_{2}$$Nb$$_{2}$$O$$_{6}$$F suggests Nb$$_{4}$$:5+. This thesis reports a pyrochlore in the Ca$$_{2}$$Nb$$_{2}$$O$$_{6}$$F family. The compound was weakly diamagnetic and appeared to have the Niobium in a predominantly 5+ oxidation (4d0) state. These properties suggested the presence of calcium vacancies and the possibility of fluorine interstitials. Aluminum and titanium doping altered the properties of the pyrochlore. Extent: 47 pages URI: http://arks.princeton.edu/ark:/88435/dsp01x059c980w Type of Material: Princeton University Senior Theses Language: en_US Appears in Collections: Chemistry, 1926-2016