講演題目：　Effect of Hydrostatic Pressure on Magnetic States
       and Transitions in Layered Metal Oxides　Na_xCoO₂ and Sr_n+1Ru_nO_3n+1

講　師　：　Prof. Yuri Sushko
　　　　　　　　　(Department of Physics & Astronomy University of Kentucky)
　　　　　　　　 
日　時　：　平成16年9月17日（金）　11:00-
場　所　：　北海道大学大学院理学研究科物理学専攻　大学院講義室
　　　　　　　理学部　2号館（2−11号室）

要　旨　：
　 　Unconventional superconductivity, itinerant and localized moment magnetism, magnetic-field-dependent metal-insulator transitions are notorious characteristic features of transition-metal oxides, such as cuprates, manganates, ruthenates, cobaltates. Since pressure P is one of the main thermodynamic parameters, similar  to temperature and magnetic field, an external pressure is often used to tune the phase transitions of interest.
In this talk, I will introduce the method of high-resolution SQUID magnetometry under hydrostatic (He-gas) pressure and its application to the studies of effects of pressure on magnetic states and transitions in correlated electron materials with layered structure. The results on two groups of transition metal oxides will be presented: (1) the metallic ruthenates Sr₃Ru₂O₇ and Sr₄Ru₃O₁₀ with perovskite-derived structure, and (2) the cobalt oxide superconductor Na_0.35CoO₂ . 1.4 H₂O and its parent compound Na_0.75CoO₂. The observed high-pressure effects will be discussed in relation to the specifics of a crystal structure comprising weakly bound two-dimensional MO₂ (M = Ru, Co) sheets, the property responsible for a strongly anisotropic character of the electron system of the materials under investigation.

世話人　　　河本　充司 （北海道大学大学院理学研究科）
　　　　　　　　　 (Tel: 011-706-4423、atkawa@phys.sci.hokudai.ac.jp)