Magnetic and structural phase transitions in ruthenocuprates: ruthenium-strontium-europium-cerium-copper oxide

This thesis establishes that both the RuO2 and CuO2 planes are metallic for stoichiometries exhibiting superconducting and magnetic phases. The implication is that itinerant carriers that 'carry' the superconductivity also 'carry' the long-range magnetic order.; Superconductivity can be destroyed in two qualitatively different ways, first by removing carriers, similar to traditional cuprates, and also by doping with hydrogen. Hydrogen doping leads to a structural phase separation. The phase separation destroys superconductivity at carrier concentrations that would otherwise be sufficient to retain superconductivity. Both methods increase the magnetic ordering temperature, but phase separation is the stronger effect. This leads to the seeming paradox that although superconductivity and magnetic order can coexist, the same changes that destroy superconductivity enhance magnetic order.; A proposal, suggested by the data but not conclusively established, is that superconductivity is destroyed by a magnetic spin flop transition. Data are presented that establish the presence of a spin flop transition, which accompanies the destruction of superconductivity.