Investigation of the Doping effect of the Magnetic ion on the hidden ordering and Kondo effect in CeB_6

1980年，由于出现了不寻常的相变，典型的致密近藤化合物CaB_6出现了聚焦。然而，直到最近，四极和八极相互作用才在其异常低温阶段发挥重要作用。近年来，新发现的相（称为IV相）引起了人们的广泛关注，人们对其序参量进行了广泛的研究。讨论了纯八极序出现的可能性。本文对Ce_xR_<1-x>B_6（R=La,Pr,Nd）进行了详细的研究。(1) Nd掺杂对CeB_6原子AF磁有序度的影响与Pr掺杂有很大不同。Ce和Pr之间的相互作用很强，但Ce和Nd之间的相互作用却很弱。结果表明，Ce_xPr_<1-x>B_6的AF态近东态被迅速抑制，而Ce_xNd_<1-x>B_6的近东态即使在AF磁相中仍存在。(2)在Ce_<0.7>Pr_<0.3>B_6的一个有序相中，中子散射波向量与x射线波向量存在不同的有序波向量。在稀土元素中，轨道和自旋分离的可能性被怀疑是存在的，而稀土元素的强L-S耦合应该是可以预期的。(3)第IV相中R（=Pr,Nd）的掺杂引起了不寻常的新相。(4)对Ce_xR_<1-x>B_6（R=La,Pr,Nd）在零磁场和有限磁场下的热电功率进行了深入研究。获得了近藤效应与RKKY相互作用竞争的新的重要信息。

It is 1980 that the typical dense Kondo compound, CaB_6 is focused due to the appearance of the unusual phase transition. However, it is only recently that the quadrupolar and octupolar interactions play an essential role in its unusual low temperature phase. Recently, discovered new phase called as phase IV has attracted much attention and has been studied extensively to clarify its order parameter. The possibility of the appearance of the pure octupolar ordering has been discussed. In the present work, we have studied Ce_xR_<1-x>B_6(R=La,Pr,Nd) in detail and the followings are clarified. (1)The effect on the AF magnetic ordering by Nd doping in CeB_6 is very different from that by Pr doping. The interaction between Ce and Pr is strong but that between Ce and Nd is surprisingly week. As a result of that, the Kondo state in the AF state of Ce_xPr_<1-x>B_6, is suppressed rapidly but that of Ce_xNd_<1-x>B_6 survives even when the system sets in the AF magnetic phase. (2)In one ordered phase of Ce_<0.7>Pr_<0.3>B_6, the different ordering wave vector was found between the neutron scattering and X-ray one. The possibility of the separation between the orbital and spin was suspected in the rare-earth element in which the strong L-S coupling should be expected. (3)The R(=Pr,Nd) doping in phase IV induces the unusual new phase. (4)The thermoelectric power has been studied intensively in Ce_xR_<1-x>B_6(R=La,Pr,Nd) in both zero and finite magnetic fields. The new important information on the competition between the Kondo effect and RKKY interaction has been obtained.