Magnetism and Superconductivity in Ruthenate-Cuprates: New Pathways to Novel Materials

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0105398 Dabrowski A significant thrust of this project will address issues important to the materials synthesis of complex oxides ceramics and will provide superior quality research material including single crystals of novel compounds. These complex transition metal oxides exhibit strong electron-electron, electron-magnon, and electron-phonon interactions. Because of these strong interactions, conduction electrons in these systems cannot be considered separately and the collective behavior is best described in terms of highly correlated electron systems. In this context an extensive study will be made of the superconducting and magnetic properties of ruthenocuprates and magnetic properties of selected phases of non- superconducting complex oxides that contain the octahedral arrangement of Ru and 0 ions. The proposed research will also address the problem of coexistence of superconductivity and weak- ferromagnetism in ruthenocuprates, which remains unique in the family of high-temperature superconductors, since the magnetic order originates in the sublattice of d-electron Ru ions. Students in the research work will be guided through the complex process of fabrication (including our unique high- pressure oxygen synthesis capabilities that lead us recently to discovery of novel Ru1-xSr2GdCu2+xO8-d superconducting and magnetic phases) and materials characterization. Participating students will be exposed to the use of cutting-edge techniques through their involvement in experiments utilizing the X-ray synchrotron based (Advanced Photon Source) and neutron diffraction techniques at Argonne National Laboratory. Supplementary muon spin rotation experiments that provide unique insights into local magnetic structure are planned and will be facilitated by the established cooperation with research team at the Paul Sherrer lnstitut in Switzerland. Advancing the fundamental understanding and associated applications of complex transition metal oxide ceramics is constrained by the current limits of our knowledge of the complex interactions present in these systems. Study of these compounds constitutes the frontier of modern solid-state ceramics and its associated physics and chemistry. The proposed project will substantially enhance our understanding of the long-standing issue of the coexistence of magnetism and superconductivity by studies of a class of recently discovered magnetic high temperature superconductors. Our unique pathways to synthesis have led to discovery of new superconducting phases of ruthenocuprates and to significant modification of magnetic properties of complex ruthenates. Beyond investigating the properties of these materials, emphasis will be placed on studying the synthesis-structure-properties relationships and exploring processing routes for novel compounds in this class using our distinctive high-pressure oxygen synthesis capabilities. Supplementary experiments are also planned, within the frame of existing cooperative efforts, with research teams from the Paul Sherrer Institut in Switzerland and the Polish Academy of Sciences in Poland. The inclusion of students in this project will provide them with valuable, contemporary experience, training, and skill with state-of-the art instrumentation in our laboratory and in the experimental facilities of Argonne National Laboratory (cutting-edge X-ray synchrotron radiation based techniques at the Advanced Photon Source and neutron diffraction experiments at the Intense Pulsed Neutron Source).