Design of new material by control of the orbital phase transition

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In order to reveal the various properties influenced by p and f electrons, this project has designed new functional materials by performing the research of systems including p and f electrons with "design of new material by controlling orbital phase transition" taken as purpose. In particular, the discovery of superconductivity in MgB_2 and elucidation of its fundamental properties was important results. It was cleared that the 2 dimensional sheet formed by B atoms in this material much contribute to the occurrence of superconductivity. Because of the charge transfer between ヲミ and ヲメ orbital at superconducting state, the charge density changed before and after superconducting transition from MEM/Rietveld analysis. Moreover, we concentrated our interest to the relationship between the superconductivity and the network formed by B atoms. From this point of view, we successfully discovered the superconductor Re_3B and Re_7B_3 in Re-B system and W_7Re_<13>B of which crystal structure was … More stabilized by B atoms and elucidated the fundamental properties of these new materials. It has not been possible to grow large single crystal and elucidate the physical properties using single crystal, however, the project has performed the pioneering role in the design of new material. Because the strong covalent bonding nature of B atoms that mediated by sp orbital control the physical properties in MgB_2, this material is extremely unique.On the other hand, we discovered the ferromagnetism in CaB_2C_2 with no magnetic elements. But we have not excluded the possibility that Fe impurities may play an important role and the influence by strong sample dependence. However, it was considered that the local distortion of crystal structure was related to magnetism in this material by the fine crystal structure analysis. More inspection is needed for supporting this result.For f electron systems, we have revealed the physical properties and the orbital ordering in CeB_6 and related materials. In particular, we have observed that magnetic moment in CeB_6 existed among Ce site. Less