Fermi Surfaces of Magnetic Uranium Compounds

磁性铀化合物的费米面

基本信息

批准号：
06640471
负责人：
HASEGAWA Akira
金额：
$ 1.34万
依托单位：
Niigata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

项目摘要

In order to carry out quantitative calculations of the electronic energy band structure for rare-earth and actinide compounds efficiently, a relativistic linearized augmented-plane-wave (RLAPW) method is made. The RLAPW method is applied to the cubic Laves phase Ce compounds such as CeRu_2, CeCo_2 and CeRh_2 which belong to the valence fluctuation regime. The energy band structures are calculated, and the Fermi surface is constructed. The Fermi surface consists of various sheets in each compound, which explain reasonably well the experimental results for the de Haas-van Alphen (dHvA) effect except the cyclotron effective masses. The same method is applied to calculate the energy band structure and the Fermi surface for the heavy-fermion U compound UPt_3. Although the experimental results for the dHvA effect are explained qualitatively well, there remain some dHvA branches whose origins are not clear. This result implies the limitations of the method, because it neglects the antiferromagnetic structure which exists in UPt_3 in reality. Then, in order to calculate the relativistic and spin-polarized energy band structure, the usual density-functional theory is extended to a relativistic current-and spin-density-functional theory for the system of interacting electrons in an external electromagnetic field. The number density, the spin density and the orbital current density are used as basic variables to describe the Hamiltonian of the system. A generalized Hohenberg-Kohn theorem is shown to hold, and a single-particle equation of the Kohn-Sham-Dirac type is derived. The single-particle equation is represented in the form which is appropriate to an isolated atom or ion, and has the magnetic interaction similar to the Zeeman term in which the spin and the orbital angular momenta couple with an effective magnetic field. The single-particle equation can be formulated also for the electrons in a crystal, and the application of the RLAPW method to it is now in progress.

为了高效地对稀土和锕系化合物的电子能带结构进行定量计算，提出了相对论线性化增强平面波(RLAPW)方法。 RLAPW方法适用于属于价态波动区的立方Laves相Ce化合物，如CeRu_2、CeCo_2和CeRh_2。计算能带结构，并构建费米面。费米面由每种化合物中的不同片层组成，可以很好地解释除回旋加速器有效质量之外的德哈斯-范阿尔芬 (dHvA) 效应的实验结果。采用同样的方法计算重费米子U化合物UPt_3的能带结构和费米面。尽管 dHvA 效应的实验结果得到了很好的定性解释，但仍有一些 dHvA 分支的起源尚不清楚。这一结果暗示了该方法的局限性，因为它忽略了现实中UPt_3中存在的反铁磁结构。然后，为了计算相对论和自旋极化能带结构，通常的密度泛函理论被扩展到外部电磁场中相互作用的电子系统的相对论电流和自旋密度泛函理论。采用数密度、自旋密度和轨道电流密度作为基本变量来描述系统的哈密顿量。广义的 Hohenberg-Kohn 定理被证明成立，并导出了 Kohn-Sham-Dirac 型的单粒子方程。单粒子方程以适合孤立原子或离子的形式表示，并且具有类似于塞曼项的磁相互作用，其中自旋和轨道角动量与有效磁场耦合。晶体中的电子也可以建立单粒子方程，并且 RLAPW 方法的应用目前正在进行中。