2001 Fiscal Year Final Research Report Summary
Study of noble electronic phases in the low-carrier strongly correlated systems under extreme conditions by diffraction techniques
| Project/Area Number |
10304030
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 | TOKYO METROPOLITAN UNIVERSITY |
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Principal Investigator |
KOHGI Masahumi Tokyo Metropolitan University, Graduate school of science, Professor, 理学研究科, 教授 (30004451)
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| Co-Investigator(Kenkyū-buntansha) |
KUWAHARA Keitaro Tokyo Metropolitan University, Graduate school of science, Assistant, 理学研究科, 助手 (90315747)
IWASA Kazuaki Tokyo Metropolitan University, Graduate school of science, Assistant, 理学研究科, 助手 (00275009)
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| Project Period (FY) |
1998 – 2001
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| Keywords | charge ordering / heavy electron / valence fluctuation / Ce monopnictide / Yb_4As_3 / low carrier / magnetic polaron / X-ray diffraction / neutron scattering |
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| Research Abstract |
The purpose of the present research is to clarify the physics behind the novel phenomena exhibited by the low-carrier strongly correlated electron systems such as Ce-monopnictides and Yb_4As_3 by neutron scattering and X-ray diffraction. The main results of the project are as follows :
(1) We have revealed by neutron and X-ray diffraction under high pressures as well as under magnetic fields that, in the magnetic ordered state of Ce-monopnictide (CeP, CeAs, CeSb), ferromangnetic layers of almost fully polarized Ce ions appear periodically in the lattice of Ce ions with the Γ_7 crystal field ground state with small magnetic moment. It is shown that the dependence of the magnetic structure of Ce-monopnictides on material as well as on applied pressure can be interpreted as its dependence on the carrier density. These findings support the idea that the exotic properties of Ce-monopnictides originate from the magnetic polaron effect mediated by the p-f mixing effect inherent in the compound
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(2) In the previous neutron scattering studies on Yb_4As_3, we showed that the material undergoes the charge order transition at 290K, and that the one-dimensional Yb^<3+> chains caused by the charge ordering exhibit one-dimensional quantum magnetism explained well by the S=l/2 ID Heisenberg model. However, it was a puzzle that the measurements of macroscopic properties such as specific heat indicate the opening of an energy gap under magnetic field being inconsistent with the model. We performed the inelastic and polarized neutron scattering experiments under magnetic field and observed directly the opening of the gap in the spin excitation spectrum. It was also found that the magnetic field dependence of the energy gap observed in our work agrees well with the theory which treats the gap opening phenomenon by applying the conformal field theory to the staggered field effect due to the Dzyalosinsky-Moriya interaction between Yb^<3+> ion pairs in the chains. These facts show that Yb_4As_3 is regarded as a new model material to study the low dimensional quantum magnetism which is firstly found among the rare-earth materials although the role of the very low carrier in the system is still unclear. Less
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