2002 Fiscal Year Final Research Report Summary
Ordering and Dynamics of Multipolar Moments
| Project/Area Number |
13640381
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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 |
物性一般(含基礎論)
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| Research Institution | Kobe University |
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Principal Investigator |
SHIBA Hiroyuki Faculty of Science, Professor, 理学部, 教授 (30028196)
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| Project Period (FY) |
2001 – 2002
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| Keywords | charge ordering / quadrupolar order / octupolar order / multipolar moment / neutron scattering / CeB_6 / Yb_4As_3 / NpO_2 |
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| Research Abstract |
The main results in this project are as follows.
The charge ordering may be viewed as the zeroth-order multipolar ordering. From this viewpoint we studied the charge ordering of Yb4As3, in which one-dimensional chains of Yb^<3+> ions are formed. We have carefully derived a low-energy effective Hamiltonian to describe the one-dimensional chain. As a result, we have succeeded in showing the presence of Dzyloshinksy-Moriya term due to the unique structure of this material. Moreover, the nature of the excitation spectrum in the chain has been studied in detail and compared with available neutron-scattering experiments.
The most important problem in this project was to study multipolar dynamics in quadrupolar order phase of CeB6. The equilibrium properties of the quadrupolar order were studied by us before. Under this project we extended our study for dynamics, which can be explored experimentally by applying the magnetic field and by using neutron scattering. In fact A. Bouvet carried out such an experiment 10 years ago in his Ph. D. thesis. Because of lack of any reliable theory at that time his experimental results have not been seriously analyzed. According to our theory field-induced staggered octupolar moments are important in CeB6. We have compared our theory with Bouvet's experiment and have achieved a good agreement.
As a third topic, we studied in general materials having Γ8 crystal-field ground state. They include TmTe and NpO2. In such systems multipolar moments beyond quadrupolar ones are crucial. We have studied interactions between multipolar moments using the symmetry of the crystal structure. In addition we have examined field-induced antiferromagnetic moments in TmTe and have explained some of the features observed in experiment.
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