Polarization and ordering of conduction bands in highly concentrated f-electron systems

从理论上研究了f-电子系统的各种有序现象和动力学，特别注意了传导电子自旋自由度的作用，得到以下结果：1. CeRh 3B 2具有Ce化合物中最高的居里温度（120 K），并表现出传导电子的反向极化、强各向异性和小磁矩等各种异常现象.我们提出了一个考虑Rh的4d分子轨道与Ce离子的4f电子混合的模型，并用平带机制解释了这种铁磁性。2.我们确定了Cel-xLaxB 6的第四相的序参量为磁八极，这是一个长期的谜团。我们的模型解释最近的X射线散射结果一致。本文成为J.Phys.Soc.Jpn的编辑推荐文章，并被媒体报道。3.推导了用动力学平均场理论计算能带的公式，并编制了相应的程序。以前的理论不能考虑重要的自旋轨道相互作用和晶体电场效应。通过扩展NCA方法，并将其纳入LMTO能带计算，进行了定量计算。4.用中子散射方法对三元Np化合物NpTGa_5（T=Co，Ni，Rh）进行了研究。我们提出了一个统一的模型，可以解释这些化合物的各种磁序，并解释自然复杂的有序状态。Np轨道自由度被确定为各种磁序的来源，并预测了与磁序相关的晶体形变。5.我们提出Pr方钴矿的序参数为标量型，保持晶体的立方对称性。我们的模型自然地解释了核磁共振特性，如依赖于磁场方向，磁化强度的各向异性，各向同性磁化率。

Variety of ordering phenomena and dynamics of f-electron systems were theoretically investigated paying special attention to the role of the spin degree of freedom of the conduction electrons, and following results were obtained.1.CeRh3B2 has the highest Curie temperature (120 K) as Ce compounds, and shows various anomalies such as the reverse-polarization of conduction electrons, strong anisotropy, and a small moment. We proposed a model which respects mixture between 4d molecular orbitals of Rh and 4f electron of flanking Ce ions, and explained this ferromagnetism in terms of a flat band mechanism.2.We have identified the order parameter of the phase IV of Cel-xLaxB6 as magnetic octupoles, which has been a longstanding mystery. Our model explains recent X-ray scattering results consistently. Our paper became an Editors' Choice in J.Phys.Soc.Jpn, and was reported by the press.3.The band calculation by dynamical mean-field theory was formulated, and the program code was developed. Previous theories could not take account of important spin-orbit interaction and the crystalline electric field effects. Quantitative calculations were performed by extending the NCA method, and incorporating this in the LMTO band calculation.4.Ternary Np compounds NpTGa5(T=Co, Ni, Rh) have been actively studied by neutron scattering. We have proposed a unified model that can explain a variety of magnetic orders of these compounds, and explained naturally complex ordered states. The Np orbital degrees of freedom are identified as the source of various magnetic orders, and a crystal deformation was predicted associated with the order.5.We have proposed the order parameters of Pr skutterudites as the scalar-type that keeps the cubic symmetry of the crystal. Our model naturally explains the NMR characteristics such as dependence on magnetic field direction, the anisotropy of the magnetization, and isotropic susceptibility.