| Co-Investigator(Kenkyū-buntansha) |
KOJIMA Kenichi Hiroshima University, Faculty of Integrated Arts and Sciences, Assistant, 総合科学部, 助手 (00100975)
HIHARA Tadamiki Hiroshima University, Faculty of Integrated Arts and Sciences, Professor, 総合科学部, 教授 (30004279)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1989: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1988: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
In the course of our research on new Kondo compounds, we have found that isostructural ternary compounds CeTIn with T=Ni, Pd and Pt display such interesting properties as Kondo lattice or valence-fluctuating states depending on the degree of mixing of f-electrons with the ligand s, p or d-electron states near the Fermi energy. The results obtained using polycrystals are summarized as follows. (1) CeNiSn is a valence-fluctuating system with Kondo-like behavior, (2) CePdIn, is an antiferromagnetic heavy-fermion system with T_N=1.8 K (Cm/T -700 mJ/mole.K^2 at T=50 mK) and (3) CePtIn is a nonmagnetic heavy-fermion compound with Cm/T -500 mJ/mole.K^2 at T=50 mK and show no sign of any phase transition down to 50 mK. All of these compounds crystallize in a hexagonal Fe_2p-type structure. Since the Ce atoms have both the nearest Ce and ligand atoms in the same c-plane, the network of Ce atoms can be considered to be nearly two-dimensional. In such a two-dimensional network, we can expect a hu
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ge anisotropy in transport, magnetic and thermal properties.
In this project, we planned to make single crystals of CeTIn and to measure the magnetic susceptibility, electrical resistivity, thermoelectric power, thermal expansion and elastic constants. We succeeded to grow single crystals of CeNiIn and CePdIn by a Czochralski method using a triarc furnace made by hand, except for CePtIn. The results obtained using single crystals are summarized as follows. InCeNiln, the a-axis resistivity rho_a has a single-peak around 120 K and a lnT dependence in the high temperature region, whereas rho_c decreases with decreasing temperature like metal without any anomaly. For CePdIn, rho_a exhibits a double-peak structure characteristic of the Kondo lattice system, while rho_c is about one half of rho_a in magnitude and the double-peak structure is smeared out. These results indicate that the Kondo - scattering is more significant in the plane perpendicular to the c-axis than along the c-axis, which may come from anisotropic hybridizations of 4f-electrons with ligand s, p or d-electron states. However, such anisotropic hybridization effects subtractively act on the crystalline electric field (CEF) effects in the anisotropy of the susceptibility for both CeNiIn and CePdIn. This may reflect the anisotropic shape in spatial extension of Ce 4f-electrous around the quantization axis J in the ground state. Less
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