1996 Fiscal Year Final Research Report Summary
Fermi Surfaces of Magnetic Uranium Compounds
| Project/Area Number |
06640471
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Niigata University |
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Principal Investigator |
HASEGAWA Akira Niigata University, Faculty of Science, Professer, 理学部, 教授 (40004329)
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| Project Period (FY) |
1994 – 1996
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| Keywords | uranium compounds / cerium compounds / relativistic current-and spin-density functional theory / single-particle equation / electronic energy band structure / Fermi surface |
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| Research Abstract |
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.
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