Studies of multipole ordering and the dimer ground state in the rare-earth compounds

对于呈现多极有序的CeB_6体系，我们成功地用共振X射线散射直接观测到了O_（1-x）和Txyz的有序参数<xy>。通过对Ce_ La_ B_6第IV相的压力效应的研究<0. 8><0. 2>，发现这一结果很难用以前提出的八极序来理解。对于CeT_2Al_（1-x）体系<10>，我们发现该体系的有序起源是磁性的，自旋单态与长程有序密切相关，电子态具有二维性质，各向异性的c-f杂化对反常的长程有序起着重要作用。

As for CeB_6 system showing a multipole order, we succeeded to observe the order parameters of O_<xy> and Txyz directly by the resonant X-ray scattering. By the study of the pressure effect on phase IV of Ce_<0. 8> La_<0. 2> B_6, we found that the results were difficult to understand by the octupole order proposed previously. As for CeT_2Al_<10>, we found that the origin of the order is magnetic, the spin singlet is closely associated with the long range order in this system, the electronic state has a two-dimensional nature and the anisotropic c-f hybridization plays an important role in the unusual long range order.