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藤森 伸一
no journal, ,
We have studied the electronic structure of UTe by means of resonant photoelectron spectroscopy (RPES) and angle-resolved photoelectron spectroscopy (ARPES). The partial U~
density of states of UTe were imaged by the U~
- RPES and it was found that the U~ state has an itinerant character, but there exists an incoherent peak due to the strong electron correlation effects. The band structure of UTe was obtained by ARPES, and its overall band structure was mostly explained by band structure calculations, except for the incoherent band at 
eV. These results suggest that the U~ states of UTe have itinerant but strongly-correlated nature. In addition, the valence state of UTe was studied by core-level photoelectron spectroscopy. The main peak position of the U 4f core-level spectrum of UTe coincides with that of UB, which is an itinerant compound with a nearly 5
configuration. However, the main peak of UTe is broader than that of UB, and satellite structures are observed in the higher binding energy side of the main peak, which are characteristics of mixed-valence uranium compounds. These results suggest that the U~ state in UTe is in a mixed valence state with a dominant contribution from the itinerant 5 configuration.
Si神戸 振作
no journal, ,
URuSiの隠れた秩序について考察する。最近の研究により、隠れた秩序状態の電子状態対称性はいくつかの空間群に限られている。しかし、それは同じ高い対称性を持つため、その区別は依然として困難である。そのため一軸圧力などの外場によって、隠れた秩序状態の対称性がどのように下がるか見る必要がある。本研究では一軸圧を[100]方向にかけて斜方晶にしたときのRu-NQRについて議論する。
Te
Opletal, P.; 酒井 宏典; 芳賀 芳範; 常盤 欣文; 山本 悦嗣; 神戸 振作; 徳永 陽
no journal, ,
Uranium chalcogenides is a large group with many interesting compounds. Some of the examples are 
-US in which metallic state can be induced by magnetic field, and newly discovered spin-triplet superconductor UTe which exhibits complex phase diagram in applied magnetic field and in hydrostatic pressure. One of the compounds belonging to the group is UTe which crystallizes in noncentrosymmetric P-6 (174) space group. The crystal structure is complicated with three unequal positions for uranium atoms and four unequal positions for tellurium atoms. Complex uranium systems were recently suggested to host heavy-fermion behavior by Svanidze et. al. Published magnetic properties of polycrystalline sample suggest ferromagnetic behavior with Curie temperature of 54 K. We present magnetic, transport and thermodynamic results obtained on single crystal of UTe. Single crystals were obtained by chemical vapor transport method. UTe shows ferromagnetic ordering of magnetic moments in basal plane below 48 K. Around 26 K additional ordering is observed in the c-axis direction. Electric transport shows semimetallic behavior. We will discuss unusual behavior of magnetism in connection with crystal structure and unequal uranium positions.
Zn
北澤 崇文; 芳賀 芳範
no journal, ,
Yb希薄系(Lu,Yb)RhZnは、基底状態として多重縮重の近藤一重項をとる不純物近藤系である。筆頭発表者は、この物質が近藤磁場よりも十分に低い磁場で磁気異方性が発達することを見出した。磁気異方性の発達過程を調べるため、現在、磁化および比熱のパルス強磁場実験を行っている。講演では、改良した磁化測定手法、および、比熱の磁気異方性を中心にパルス強磁場実験の進捗状況を発表する。
芳賀 芳範
no journal, ,
Preparation of high-quality single crystal, characterization and superconducting properties will be shown. In particular, extremely enhanced upper critical fields are discussed.
-
phase diagram of spin-triplet superconducting UTe酒井 宏典
no journal, ,
スピン三重項超伝導体として注目されているUTeにおける新しい単結晶育成法を考案し、その条件最適化をおこなった結果、超伝導転移温度の向上に加えて、残留抵抗率比の大幅な改善がみられた。こうして得られた純良単結晶を用いて、電気抵抗率と交流帯磁率の同時測定を行なって強磁場25Tまでの磁場()-温度()相図の決定を行った。