2004 Fiscal Year Final Research Report Summary
Neutron Scattering Study on Ferromagnetism and Superconductivity.
| Project/Area Number |
14340112
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Japan Atomic Energy Research Institut |
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Principal Investigator |
METOKI Naoto Japan Atpmic Energy Research institute, Advanced Scence Research Center, Ptincipal Scientist, 先端基礎研究センター, 主任研究員 (40343909)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO Koji Japan Atomic Energy Research institue, Advanced Science Research Center, Researcher, 先端基礎研究センター, 研究員 (30370381)
HAGA Yoshinori Japan Atomic Energy Research instute, Advanced Seience Research Centar, Senior Scientist, 先端基礎研究センター, 副主任研究員 (90354901)
YAMAMOTO Etsuji Japan Atomic Energy Research institute, Advanced Science Research Center, Senior Scientist, 先端基礎研究センター, 副主任研究員 (50343934)
MATSUDA Tatsuma Japan Atomic Energy Research institute, Advanced Science Research Center, Researcher, 先端基礎研究センター, 研究員 (30370472)
ONUKI Yoshichika Osaka University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (40118659)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Uranium / Neutron Scattering / Superconductivity / Ferromagnetic / Antiferromagnetic / Quadrupole / Orbital / Neptnium |
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| Research Abstract |
The multiple detector/analyzer system as well as χ-circle goniometer was constructed for high-efficiency elastic and inelastic neutron scattering experiments of ferromagnetic superconductors. We have revealed the coexistence of the ferro- and antiferromagnetic order and the magnetic phase diagram of a localized 5f compound U_3Pd_<20>Si_6. A new type of magnetic order and the metamagnetic transition have been discovered with high field experiment. Quasi-elastic scattering was observed, very close to the antiferromagnetic vector, indicative of a n itinerant 5f part coexisting with localized 5f configuration. The field induced antiferroquadrupolar ordering with O_<xy> type order parameter based on the pseudo-quartet state due to singlet Γ_1 ground and triplet Γ_4 excited states has been clarified very close to the superconducting phase. We observed quasi-elastic scattering coupled with CEF excitation, both exhibits significant change with the superconducting transition. The observed dispe
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rsion relation indicates the dominant role of the many body quadrupolar interactions between heavy conduction electron hybridized with f electrons. We also search for ferromagnetic fluctnations. Itinerant 5f antiferromagnets U115 and Np115 have been systematically studied by means of neutron scattering. We have revealed magnetic structures, which is highly sensitive to the number of d-electrons, FM, A-, C-, G- type antiferomagnetic structures have been clarified, reminiscent of the Mn perovskite, where charge, spin and the orbital degree-of-freedom play an important role. We found that the double successive transition in NpTGa_5 is accompanied by the transition of the 5f electronic state. This electronic transition would be due to the competing magnetic and quadrupolar interactions between different 5f orbitals. We discovered the coexistence of the superconductivity and a static and long rage antiferromagnetic order with very small Ce moment 0.17μB in the non-centrosymmetric heavy ferrmion superconductor CePt_3Si. The pseudo-quartet ground state Γ_8 quartet in cubic symmetry splits very weakly (〜1meV) by the tetragonal crystal symmetry, where the energy scale of the splitting is in the same order as those for Kondo temperature. It should be noted that the pseudo-quartet state possesses both magnetic and quadrupolar degree-of-freedom. The lack of inversion symmetry makes the p-wave superconductivity difficult, whereas, the p-wave pairing is realized on the ferromagnetic basal plane, involving inversion center. We observed a quasi-elastic line shape at the vicinity of the antiferromagnetic propagation vector q=(001/2), coupled with dispersive spinwave. No significant change in the quasi-elastic scattering was detected above and below the superconducting temperature. Less
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