| Project/Area Number |
04452051
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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 |
物性一般（含極低温･固体物性に対する理論）
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| Research Institution | Osaka University |
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Principal Investigator |
ASAYAMA Kunisuke Osaka Univ., Faculty of Eng.Sci., Prof., 基礎工学部, 教授 (20029416)
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| Co-Investigator(Kenkyū-buntansha) |
ZHENG Guo-qing Osaka Univ., Faculty of Eng.Sci., Res.Assoc., 基礎工学部, 助手 (50231444)
KITAOKA Yoshio Osaka Univ., Faculty of Eng.Sci., Assoc.Prof., 基礎工学部, 助教授 (70110707)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 1993: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1992: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Keywords | NMR / Heavy Fermion / Superconductor / Magnetic Transition / NQR / UPd_2Al_3 / UNi_2Al_3 / CePd_2Al_3 / 重い電子系超伝導 / 核磁気共鳴 |
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| Research Abstract |
NMR and NQR studies on two newly-discovered antiferromagnetic heavy-fermion superconductors, UNi_2Al_3 and UPd_2Al_3 with T_c = 1 and 2K and T_N =4.2K and 14K, respectively, have revealed that the type of magnetic fluctuation and spin structure of these two compounds belong to different classes. UNi_2Al_3 possesses a unique feature where the low-energy spin fluctuations survive in a low-T region, keeping a strong wave-number dependence. This is the first case in the magnetic actinide system. The spin structure is presumably of a helical spin type where the magnetic field causes a partial canting of an assembly of spins to the direction of the magnetic easy plane. In UPd_2Al_3, there emerges a partial energy gap on the Fermi surface below T_N, while the low temperature properties are governed by the Fermi liquid excitation associated with the residual density of states. The spin structure is of a commensurate type where the ferromagnetic sheets directed in the magnetic easy plane couple antiferromagnetically along the hexagonal caxis. It should, however, be noted that the magnetic moments, 0.85mu_B for UPd_2Al_3 is by one order of magnitude larger than 0.03mu_B for URu_2Si_2, while the magnetic or electronic energy gap is rather by one-half smaller.
The unstablesuperconducting property of UNi_2Al_3 in powder sample in comparison with UPd_2Al_3 may be related to the unique magnetic nature of UNi_2Al_3. The superconductivity in UPd_2Al_3 is in a clean limit with dominant singlet pairing. This means that the impurity scattering plays a minor role and hence the pseudo-spin momentum is preserved in the pairing state. The superconducting energy gap is of an anisotropic type where the gap vanishes on lines at the Fermi surface. Apparently, the unique relaxation behavior in the heavy fermion superconductors is consistently described in terms of a universal gapless model, irrespective of the variety of the magnetic and normal state properties.
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