| Project/Area Number |
15540326
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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 |
Condensed matter physics II
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| Research Institution | Tohoku University |
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Principal Investigator |
NAKAMURA Shintaro Tohoku University, Center for Low Temperature Science, Research Associate, 極低温科学センター, 助手 (20292310)
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| Co-Investigator(Kenkyū-buntansha) |
AOKI Haruyoshi Tohoku University, Center for Low Temperature Science, Professor, 極低温科学センター, 教授 (60302246)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2003: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | non Fermi liquid / quantum phase transition / heavy fermion / multipole moments / Kondo effect / electrical resistivity / dHvA effect / 多重極秩序 / Ce_xLa_<1-x>B_6 / 強相関係 / 近藤効果 |
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| Research Abstract |
CexLa1-xB6 is a Kondo system where the ground crystal electric field state of 4f electrons (a Gamma 8) carries both magnetic dipolar and electric quadrupolar degrees of freedom. It is well known that the ground state of the CexLa1-xB6 is a local Fermi liquid when the Ce concentration is very low. We have investigated the electronic phase diagram of this system with changing the Ce concentration and magnetic fields.
Through the measurements of electrical resistivity at very low temperature, we have found that the ground state of CexLa1-xB6 changes from the local Fermi liquid state to a non Fermi liquid state with increasing the Ce concentration. This behavior is quite different from that of CexLa1-xCu6 where the gradual change from a local Fermi liquid to a heavy fermion occurs. In the case of CexLa1-xB6, this non Fermi liquid is instable in high magnetic fields. The electrical resistivity of CexLa1-xB6 shows Fermi liquid behavior under high fields at every Ce concentration. We have confirmed this point by the observation of the de Haas-van Alphen (dHvA) effect. The dHvA oscillation is observed in every Ce concentration. The effective mass obtained is well scaled by the Ce concentration and the mass diverges with decreasing the magnetic fields. This probably indicates that the Fermi liquid state becomes instable with decreasing the magnetic fields.
When the Ce concentration x becomes higher than 0.6, CexLa1-xB6 at zero field undergoes a quantum phase transition from the non Fermi liquid to a long range ordered state. In the long range ordered state the electrical resistivity shows Fermi liquid behavior. In the present study we have found that the high magnetic fields and the long range ordering stabilize the Fermi liquid state in the CexLa1-xB6 system. This suggests that the origin of the non Fermi liquid in CexLa1-xB6 is the fluctuation of the local moments of 4f electrons.
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