2004 Fiscal Year Final Research Report Summary
Impurity Effects on Quadrupolar Ordering in Pr-based Compounds
| Project/Area Number |
14540340
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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 | KYUSHU UNIVERSITY |
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Principal Investigator |
KAWAE Tatsuya Kyushu University, Faculty of Engineering, Associate Professor, 大学院・工学研究院, 助教授 (30253503)
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| Co-Investigator(Kenkyū-buntansha) |
HITAKA Masako Kyushu University, Faculty of Engineering, Research Associate, 大学院・工学研究院, 助手 (00264094)
TANAKA Akinori Kyushu University, Faculty of Engineering, Research Associate, 大学院・工学研究院, 助手 (80274512)
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| Project Period (FY) |
2002 – 2004
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| Keywords | strongly correlated electron system / quadrupolar moment / quadrupolar glass / Kondo effect / quadrupolar ordering |
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| Research Abstract |
We have investigated the low-temperature properties of Pr$_{x}$La$_{1-x}$Pb$_{3}$ with the $Gamma_{3}$ doublet in the CEF ground state for the whole range of Pr concentration. The specific heat represents three different features depending on the Pr concentration. In the very dilute Pr concentration of $x$$le$0.05 NFL behavior was found. The specific heat $C/T$ for $x$$le$0.05 increases monotonically below $T$=1.5 K, which can be scaled with a characteristic temperature $T$* defined at each concentration $x$. This demonstrates that NFL behavior should be explained by the single-ion model of the $Gamma_{3}$ moment. The electrical resistivity $rho$($T$) for $x$$le$0.05 represents a marked decrease deviating from a Fermi-liquid behavior $rho$($T$)$propto$$T^{2}$ in the temperature region where NFL behavior was observed in the specific heat. The observed features strongly suggest that the Kondo effect arising from the correlation between the $Gamma_{3}$ moments and the conduction electrons
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is responsible for NFL behavior for $x$$le$0.05. In addition, the novel features observed in the Pr concentration for $x$$ge$0.1 are explained by assuming the correlation between the $Gamma_{3}$ moments and the conduction electrons as follows. In PrPb$_{3}$, the antiferroquadrupolar ordering with the transition temperature at $T_{Q}$=0.4 K exhibits a modulated structure even below $T$=0.1 K for $H$$<$1T~cite{17}. Furthermore, the ordering exists only for the Pr concentration larger than $x$$sim$0.98. These facts indicate the presence of the long-range interaction, which is probably mediated by the conduction electrons. For a wide range of Pr concentration for 0.1$le$$x$$le$0.95, the specific heat shows a $T$-linear variation with a large $gamma$-coefficient, which is almost reproduced by the model for amorphous materials with a random configuration of two-level system. This fact suggests that a glass-like state is realized due to the competition of two interactions, (i) the interaction between the $Gamma_{3}$ moments and (ii) the interaction between the $Gamma_{3}$ moments and the conduction electrons. Less
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