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

对于表现出多极有序的CeB_6体系，我们成功地用共振X射线散射直接观测到了O_&lt；xy&gt；和Txyz的有序参数。研究了压力对Ce&lt；0.8；La_&lt；0。2&gt；B_6，我们发现结果很难用先前提出的八极序来解释。对于CET_2Al_&lt；10&gt；，我们发现有序的起源是磁性的，自旋单态与长程有序密切相关，电子态具有二维性，各向异性的c-f杂化在反常长程有序中起着重要作用。

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.