Theoretical Study on Itinerant Electron Systems Containing Transition-Metal, Rare-Earth, and Actinide Elements

1.用自洽的APW或KKR方法计算了典型的过渡金属、稀土和榄系元素化合物在非磁态和磁态下的电子能带结构。重点研究了NiAs型、立方钙钛矿型、Laves相和含3d电子的插层化合物。在所获得的能带结构的基础上，考虑了自旋涨落，研究了这些化合物的磁性。通过比较各相的总能量，讨论了晶体结构和磁序的稳定性。对于含4f和5d电子的Ce和U化合物，详细研究了自旋-普里比相互作用对能带态的影响。对La_2CuO_4进行了能带计算，以获得有关高T_c氧化物超导体的特征方面的信息。在有限温度下，自旋起伏对巡回电子系统的磁性起着至关重要的作用。Moriya发展的自洽重整化理论成功地解释了金属间化合物CrB_2和YMn_2的磁学性质。此外，自旋涨落的统一理论被用于研究NiAs类化合物的反常磁性，如MnAs和CoAs，以及Ni3的表面磁性。强电子关联在重电子系统中是极其重要的，例如Ce化合物和榄系化合物，以及高T_c氧化物超导体。将基于周期Anderson模型的费米液体理论推广到考虑晶场和自旋-轨道相互作用的情况。用单位杂质Anderson模型对Ce和La化合物的光电子能谱进行了理论分析。人们致力于阐明电子关联在高T_c氧化物超导体中的作用。

1. Electronic band structures of typical compounds containing transiton-metal, rare-earth, and actinide elements are calculated for the non-magnetic and magnetic states by a selfconsistent APW or KKR method. NiAs-type, cubic perovskite-type, Laves phase, and intercalation compounds containing 3d electrons are studied intensively. On the basis of the obtained band structures, magnetic properties of these compounds have been studied by taking account of spin fluctuations. Also a stability of the crystal structure and of the magnetic ordering is discussed by comparing the total energy of each phase. For Ce and U compounds containing 4f and 5d electrons, the effects of the spin-prbit interaction on the energy band states are investigated in detail. Band calculation of La_2CuO_4 has been performed in order to derive information about the characteristic aspects of the high-T_c oxide superconductor.2. Spin flluctuations play an essential role in the magnetism of itinerant electron systems at finite temperatures. The self-consistent renormalization theory developed by Moriya has provided a successful understanding of the observed mangetic properties of intermetallic compounds such as CrB_2 and YMn_2. Furhtermore, the unified theory of spin fluctuations is used in the study of anomalous magnetic properties of the NiAs-type compounds such as MnAs and CoAs, and of the surface magnetism of Ni.3. A strong electron correlation is extremely important in heavy-electron systems such as Ce compounds and actinide compounds and in high-T_c oxide superconductors. The Fermi liquid theory based on the perodic anderson model is extended to the case including the crystalline field and the spin-orbit interaction. Theoretical analyses of phototelectron spectroscopy in Ce and La compounds have been made by using the isngle-site impurity Anderson model.. A considerable ellort has been devoted to making clear a role of electron correlation in high-T_c oxide superconductors.