1997 Fiscal Year Final Research Report Summary
^<13>C NMR in borocarbide superconductor
| Project/Area Number |
08640464
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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 | The University of Tokushima |
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Principal Investigator |
MIZUNO Kiyoshi Faculty of Arts and Sciences The University of Tokushima Professor, 総合科学部, 教授 (40087094)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Takahito Faculty of Arts and Sciences The University of Tokushima Research Associate, 総合科学部, 助手 (60201505)
KOYAMA Kuniyuki Faculty of Arts and Sciences The University of Tokushima Associate Professor, 総合科学部, 助教授 (40170394)
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| Project Period (FY) |
1996 – 1997
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| Keywords | superconductivity / spin fluctuation / electron-electron correlation / borocarbide / NMR / spin-lattice relaxation time / BCS / BCS |
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| Research Abstract |
Quaternary borocarbide intermetallic compounds RM_2B_2C (R = rare-earth element, M=transition metal element) show a relatively high superconducting transition temperature T_c The effect of electron correlation is expected to be important because the d-electron of transition metal plays a leading actor of conduction. From ^<13>C,^<11>B NMR,the detailed information on the electronic properties of borocarbide superconductor YNi_2B_2C is obtained in normal and superconducting state.
1. In the normal state, the existence of the antiferromagnetic spin fluctuation was suggested. The spin-lattice relaxation rate T_1^<-1> and Knight shift K of ^<13>C and ^<11>B NMR show that the isotropic (Fermi contact) interaction between 2s conduction electron spin and nuclear spin at the carbon site and the boron site is dominant. The temperature dependences of T_1^<-1> and K is explained well by the Korringa mechanism. These temperature dependences are attributed to that of spin susceptibility, which is the consequence of band structure. No antiferromagnetic spin fluctuation is observed in ^<13>C and ^<11>B NMR.Strength of the electro-electron interaction is the same order as that found in alkali metal. These experimental results agree well with the results of band calculation.
2. In the superconducting state, a small coherence (Hebel-Slichter) peak is obsereved, which testified the borocarbide compounds to be a conventional phonon-mediated s wave (BCS) superconductors. From the temperature dependence of <@D113@>D1CT<@D21@>D2<@D1-1@>D1, a superconducting gap parameter of 2DELTA<@D20@>D2/k<@D2B@>D2T<@D2C@>D2 = 3.30(]SY.+-。[)0.08 is obtained. The borocarbide compound being a conventional BCS superconductor is consistent with the normal properties of the Fermi liquid picture in the normal state.
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