Electronic structures of the systems with orbital degeneracy

我们已经获得了轨道自由度起重要作用的系统的高质量样品，并揭示了它们的电子结构。这些样本也提供给本项目的其他研究小组，以使用各种方法进行研究。利用光发射光谱、软x射线发射光谱和吸收光谱，揭示了高Tc化合物MgB_2及其相关化合物AlB_2的特征电子结构。采用磁测量、ESR、光发射光谱、SdH效应等方法研究了高温弱铁磁体CaB_6的异常磁性和电子结构。以前报告的大多数实验结果已被发现是不正确的。我们也对磁性杂质进行了详细的分析，但不能澄清弱铁磁性是否是本征性的。我们发现四极序CeB_6、PrPb_3和Ce_3Pd_<20>Ge_6.4体系的磁相图和电子结构在静水压力和单轴压力下发生了异常变化。我们已经通过SdH效应和核磁共振测量揭示了导电电子的电子结构和磁性离子之间的磁性相互作用，如Yb_4As_3及其合金等化合物在高温下发生电荷序跃迁。我们发现了Upd_3和U_3Pd_<20>Si_6等铀化合物的异常磁性和电子结构，它们的5f电子表现出局域性。我们还对RB_2C_2、RB_6、TmTe、稀土硫族化合物、稀土嘌呤、铀化合物等重要体系进行了广泛的研究。

We have grown high quality samples of the systems where the orbital degrees of freedom play important roles and have revealed their electronic structures. The samples were also supplied to the other research groups of the present project to perform the research using various methods.1. We have revealed characteristic electronic structures of high Tc compound MgB_2 and its related compound AlB_2 using photoemission spectroscopy and soft X-ray emission and absorption spectroscopy.2. We have studied the anomalous magnetic properties and electronic structures of high-temperature weak ferromagnet CaB_6 employing various methods such as magnetic measurements, ESR, photo emission spectroscopy, SdH effect. Most of the experimental results previously reported have been found to be incorrect. We have also performed a detailed analysis of magnetic impurities, but could not clarified whether or not the weak ferromagnetism is intrinsic.3. We have revealed anomalous changes of the magnetic phase diagrams and electronic structures with hydrostatic and uniaxial pressures for the systems with quadrupolar order, CeB_6, PrPb_3 and Ce_3Pd_<20>Ge_6.4. We have revealed the electronic structures of the conduction electrons and magnetic interactions among magnetic ions by SdH effect and NMR measurements for the compounds like Yb_4As_3 and their alloys where the charge order transition takes place at high temperatures.5. We have revealed anomalous magnetic properties and electronic structures of the U compounds like Upd_3 and U_3Pd_<20>Si_6 whose 5f electrons show localized nature.6. We have also performed extensive studies on other important systems such as RB_2C_2, RB_6, TmTe, rare earth chalcogenides, rare earth pnictides and uranium compounds.