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Résumé |
Pyrochlore-type compounds are known to exhibit attractive properties driven by geometrical frustration. Especially, some of the itinerant ones show superconductivity or metal-insulator transition. Here I will present my recent study in synthesis, structure and properties of A2Ru2O7 (A=Hg,Cd,Ca,Tl), Tl2Rh2O7, and A2Ir2O7 (A=Hg,Cd,Ca,Tl). All the compounds are prepared at 4 GPa by a cubic-anvil-type equipment. High-pressure method has advantages in suppressing the vaporization of high volatile elements, stabilize unusual valence, and keeping oxygen stoichiometry. Most of ruthenium and rhodium oxides show metal-insulator transition or kink, and iridium ones show anomalous metallic feature. I will also present transport, magnetic, and structure properties under pressure of these compounds. Results show that each compound stays in balance between cations. |
