Doped perovskite-based ruthenates: Structure, electrical, magnetic and magnetoresistive properties
The electric and magnetic properties of ruthenium-containing ABO 3 oxides with perovskite structure are intimately connected with their structure and composition. Even a slight perturbation caused by doping can significantly modify the electrical conductivity and the magnetic ground state of these compounds. In this thesis the structural, electronic, and magnetic properties of several perovskite ruthenate solid solutions, based on SrRuO 3 and CaRuO3, and containing Fe or Co on the B-sites, are presented. In the Fe-containing compounds, Ru preserves its 4+ valence state, while in the Co-doped compounds there is an order-dependent charge transfer between Ru and Co, leading to some Ru in the 5+ state. Saturation magnetization of solid solutions initially increases with both Fe and Co concentration, indicating the formation of large local magnetic moments around these cations. At higher Fe and Co substitution level, a spin glass state develops and a gradual metal/insulator transition occurs. At the same time, a large negative magnetoresistance emerges. These solid solutions are analogous to Mn-doped diluted magnetic semiconductors that contain giant local moments around Mn impurities, which themselves interact antiferromagnetically. Similar magnetic and magnetoresistive behavior is expected in other conducting ruthenates, and possibly other 4d and 5d conducting oxides that are doped with 3d transition metals.
Mamchik, Alexander Ivanovich, "Doped perovskite-based ruthenates: Structure, electrical, magnetic and magnetoresistive properties" (2003). Dissertations available from ProQuest. AAI3109200.