| Project/Area Number |
10640325
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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 | Tohoku University |
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Principal Investigator |
TAKAGI Shigeru TOHOKU UNIVERSITY, GRADUATE SCHOOL OF SCIENCE, ASSOCIATE PROFESSOR, 大学院・理学研究科, 助教授 (20154750)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Hisao TOHOKU UNIVERSITY, GRADUATE SCHOOL OF SCIENCE, RESEARCH PHYSICIST, 大学院・理学研究科, 助手 (40250675)
KAMIMURA Takashi TOHOKU UNIVERSITY, GRADUATE SCHOOL OF SCIENCE, PROFESSOR, 大学院・理学研究科, 教授 (30005813)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1999: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1998: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | DILUTE U-IMPURITY SYSTEMS / U COMPOUNDS / NMR / SPIN DYNAMICS / KONDO EFFECT |
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| Research Abstract |
(1) Dilute U Impurity Systems : Single-site properties of U ions have been investigated in dilute UAI_2 and U_2Zn_<17>, with counterpart dense compounds showing quite contrasting magnetic behavior, by using respectively two different non-magnetc matrices with significantly different lattice parameters. In all the cases, the observed behavior can be explained semi-quantitatively in terms of Kondo effect under crystal field. But differently from Ce-based 4f systems, the behavior of the dense 5f compounds cannot be described as simple collection of the U impurities in the corresponding matrices. Moreover, the variation of the characteristic energy-scale of the system is not at all monotonous against that in the lattice parameters.
(2) Systematics of the Spin Dynamics of U Compounds : The antiferromagnetic U_3Pd_<20>Si_6 (T_N=19 K) was previously characterized as a typical localized 5f moment system. In NMR measurements, we have found that the nuclear longitudinal relaxation time T_1 increases almost linearly with T above about 30 K. This indicates that the low-energy spin dynamics can be understood in terms of localized 5f moment also from the NMR viewpoint, but a strongly T-dependent, large relaxation rate of the 5f moment shows that single-site dynamics due to hybridization between 5f and conduction electrons dominate the low-energy spin dynamics in the paramagnetic state. The observed behavior has many similarities to those on U compounds with relatively high ordering temperatures such as UP, UAs and U_3P_4, and are considered as common characteristics in magnetically ordering U systems that are close to the localized moment limit.
(3) Multi-Q Magnetic Structure of U Compounds : We have found fine structures in the ^<75>As NMR spectrum at 4.2 K in the magnetically ordered double-Q type IA state. These structures are very likely to be related to the multi-Q structure, and can be an evidence for the quadrupole order in the double-Q state.
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