Exotic properties in the filled skutterudite compounds and their control by uniaxial pressure

我们一直在努力生长大尺寸、高质量的ReFe_4P_t；12&gt；，Reru_4Sb_&lt；12&gt；，REOS_4Sb_&lt；12&gt；(RE=La，Ce，Pr，Nd)单晶。在生长的晶体上，我们测量了晶体的基本物理性质，并与多个研究组就各种重要性质进行了合作研究。其中，我们简要地报道了最重要的部分，特别是在Pr基体系上。(1)PrFe_4p&lt；12&gt；：通过μSR测量进一步证实了非磁性CEF的基态。用磁场作用下的低温中子散射实验对低温有序态的铁磁和反铁磁成分进行了仔细的评价，发现该相为四极相。此外，从输运、磁性和比热测量中发现，有序状态对La取代Pr是不稳定的。(2)Pros_4Sb_&lt；12&gt；：从de Haas-van Alphen(DHvA)，它的费米表面与参考化合物LaOS_4Sb_&lt；12&gt；的费米表面接近，反映了…F-电子的局域性更强，同时我们证实了c-f杂化有望极大地增强有效质量。在核磁共振实验中，在超导带隙中既没有观察到相干峰，也没有观察到节点结构。相反，从磁场中导热系数的角度依赖关系来看，各向异性间隙与点状节点有关。此外，在超导相中还发现了两种不同对称性的不同相。通过系统的比热和磁化强度的测量和分析，发现Γ_1是最有可能的CEF基态。(3)PrRu_4p&lt；12&gt；：它是具有有趣特征(非磁性金属-绝缘体转变)的1^&lt；st&gt；Pr基填充的Skutterudite，并提出了一个嵌套模型(NM)。然而，目前还没有任何事情得到澄清。我们已经成功地检测到dHvA信号，并确定了FS。我们还成功地进行了第一个输运和比热实验，这表明只有NM不能解释M-I相变。较少

We have kept trying to grow large and high quality single crystals of REFe_4P_<12>, RERu_4Sb_<12>, REOs_4Sb_<12> (RE=La, Ce, Pr, Nd). On the grown crystals, we have measured basic physical properties and have made cooperative researches on various important properties with many research groups.Among them, we briefly report the most important part, especially on Pr-based systems.(1) PrFe_4P_<12> : Non-magnetic CEF ground state was further confirmed by μSR measurement. A careful evaluation of the ferro- and antiferro-magnetic components in the low temperature ordered state by neutron scattering experiments at low temperatures under magnetic fields revealed the phase to be a quadrupole one. Furthermore, the ordered state was found to be unstable against a replacement of Pr by La from transport, magnetic and specific heat measurements.(2) PrOs_4Sb_<12> : From de Haas-van Alphen (dHvA), its Fermi surface was found to be close to that of the reference compounds LaOs_4Sb_<12>, reflecting the … More localized nature of f-electrons, while we confirmed highly enhanced effective mass expected from c-f hybridization. In a NMR experiment, neither coherence peak nor node structure in superconducting gap has been observed. On the contrary, from the angular dependence of thermal conductivity in magnetic fields, anisotropic gap with point nodes. In addition, there found two different phase with different symmetries in the superconducting phase. From systematic measurements and analyses of specific heat and magnetization, Γ_1 was found to be the most probable CEF-ground state.(3) PrRu_4P_<12> : It is the 1^<st> Pr-based filled skutterudite exhibiting interesting feature (non-magnetic metal-insulator transition) and a nesting model (NM) was proposed to be an origin. However, nothing has been clarified yet. We have succeeded in detecting dHvA signal, and determined the FS. We have also performed the first successful transport and specific heat experiment, which suggests only the NM cannot explain the M-I transition. Less