"Moderate lattice disorder and electronic ground state properties in U heavy fermion compounds"
Dr. Stefan Sullow

Sep 30, 2004

講演題目：　Moderate lattice disorder and electronic ground state properties in U heavy fermion compounds
講　師　：　Dr. Stefan Sullow
　　　　　(Inst. fuer Metallphysik und Nukleare Festkoerperphysik TU Braunschweig, Germany)
日　時　：　平成16年9月30日 (木) 14:00-
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　：
The interplay of disorder and electronic correlations represents a　central issue of the physics of strongly correlated electron systems(SCES). The properties of SCES are extraordinarily sensitive to small levels of crystallographic disorder. This is attributed to the electronic correlations, which enhance the effect of the disorder. Correspondingly, disorder has been proposed to greatly modify or control the physical properties of SCES in very many cases. However, a thorough understanding of this issue is still lacking. Here, I present a detailed discussion of the effects of moderate crystallgraphic disorder on ground state and electronic transport properties of uranium heavy fermion compounds. For this class of systems disorder effects are particularly prominent, causing highly unusual spin glass, short range ordered or Non-Fermi Liquid ground states. From an experimental point of view, the central tasks are to determine the type and level of the disorder and to assess the influence of the disorder on the physical properties. I will address these questions within case studies on the U heavy fermion systems URh2Ge2, UPt2Si2 and related compounds.

世話人　 網塚　浩
（amiami@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究科

"Effect of Hydrostatic Pressure on Magnetic States and Transitions in Layered Metal Oxides Na_xCoO₂ and Sr_n+1Ru_nO_3n+1"
Prof. Yuri Sushko

Sep 17, 2004

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・1.4H₂O 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
（atkawa@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究科