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

1980年，CaB_6作为典型的致密Kondo化合物，由于出现了不寻常的相变而受到人们的关注。然而，直到最近，四极和八极相互作用在其不寻常的低温阶段发挥了重要作用。近年来，被称为IV相的新相的发现引起了人们的广泛关注，人们对其进行了广泛的研究，以明确其序参量。讨论了纯八极有序出现的可能性。本文对Ce_xR_<1-x>B_6（R=La，Pr，Nd）进行了详细的研究，并阐明了以下几个问题。（1）Nd掺杂对CeB_6的AF磁有序化的影响与Pr掺杂有很大的不同。Ce和Pr之间的相互作用很强，而Ce和Nd之间的相互作用却很弱。其结果是，Ce_xPr_ B_6的AF态的近藤态<1-x>被迅速抑制，而Ce_xNd_ B_6的<1-x>近藤态即使在AF磁相中仍能保持。(2)In Ce_ Pr_ B_6的一种有序相<0.7><0.3>，中子散射和X射线散射的有序波矢不同。在具有强L-S耦合的稀土元素中，怀疑轨道与自旋分离的可能性。（3）第Ⅳ相中R（=Pr，Nd）的掺杂诱导了不寻常的新相。（4）研究了Ce_xR_<1-x>B_6（R=La，Pr，Nd）在零磁场和有限磁场下的热电势。获得了Kondo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.