1988 Fiscal Year Final Research Report Summary
NMR STUDY OF HEAVY FERMION SUPERCONDUCTOR AT ULTRA LOW TEMPERATURE.
| Project/Area Number |
62460030
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | OSAKA UNIVERSITY |
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Principal Investigator |
PROFESSER ASAYAMA Kunisuke OSAKA UNIVERSITY Faculty of Engineering Science, 基礎工学部, 教授 (20029416)
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| Co-Investigator(Kenkyū-buntansha) |
ASSOCIATE Professer ODA OSAKA UNIVERSITY Faculty of Engineering Science, 基礎工学部, 助教授 (50029526)
ASSISTANT Professer KOHO HIMEJI INSTITUTE OF TECHNOLOGY, 工学基礎研究所, 講師 (10153660)
RESEARCH Assistant KITAO OSAKA UNIVERSITY Faculty of Engineering Science, 基礎工学部, 助手 (70110707)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Ultra low temperature / NMR / Heavy fermion superconductor / Anisotropic superconductor / 反強磁性 |
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| Research Abstract |
WE DEVELOPED AN ULTRA LOW TEMPERATURE NMR TECHNIQUE BY RECONSTRUCTING THE HEAT EXCHANGER AND BY CONSTRUCTING A NEW TYPE MIXING CHAMBER FOR NMR IN ^3He-^4He DILUTION REFRIGERATOR. FOLLOWING RESULTS HAVE BEEN OBTAINED BY USING THIS APPARATUS.
1. CeCu_2Si_2 THE KNIGHT SHIFT K OF Si AND Cu ARE COMFIRMED TO DECREASE TO -50% OF THE NORMAL VALUE BELOW T_c DOWN TO 60mK. TOGETHER WITH THE T^3 DEPENDENCE OF T_1^<-1> ALREADY OBSERVED, THE RESULT SHOWS A d WAVE COOPER PAIRING IS REALIZED IN THE SUPERCONDUCTING STATE.
IN THE EXTERNAL FIELD OF -3T, WHERE THE SUPERCONDUCTIVITY IS DESTROYED, THE NMR SIGNAL IS FOUND TO DECREASE WITH LOWERING TEMPERATURE, INDICATING AN ANTIFERROMAGNETIC LIKE ORDERING TO APPEAR BELOW -0.6K.
2. UPt_3 K OF Pt BELOW T_c DOES NOT CHANGE BELOW T_c DOWN TO 50 mK, WHILE T_1^<-1> OF Pt DOES NOT SHOW BCS TYPE ENHANCEMENT JUST BELOW T_c DECREASING IN PROPORTION TO T^3 AT LOW TEMPERATURE. THIS INDICATES THAT THE SUPERCONDUCTING NATURE IS EITHER SINGLET d WAVE STRONG SPIN-ORBIT SCATTERING OR TRIPLET p WAVE. PERFECT NO-CHANGE OF K SEEMS TO SUPPORT THE LATTER. NO INDICATION OF MAGNETIC ORDERING IS OBSERVED WHICH IS REPORTED BY SR AND NEUTRON DIFFRACTION MEASUREMENT.
THE ANISOTROPIC NATURE OF THE SUPERCONDUCTIVITY OBSERVED IN CeCu_2Si_2 AND UPt_3 INDICATES THE EXISTENCE OF A STRONG ON-SITE CONLOMB REPULSION. THE ANTIFERROMAGNETIC SPIN FLUCTUATIONS ARE CONSIDERED TO BE THE ORIGIN OF THE OCCURRENCE FOR THE SUPERCONDUCTIVITY.
3. CeAl_3 AND CeInCu_2 WE HAVE FOUND AN ANTIFERROMAGNETIC LIKE ORDERING IN CeAl_3 AND CeInCu_2 AT 1.2 AND 1.1K, RESPECTIVELY, FROM THE T_2 AND LINE WIDTH MEASUREMENT OF A1, Cu and In.
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