Crystal structure and Kondo lattice behavior ofCeNi9Si4
Crystal structure and Kondo lattice behavior ofCeNi9Si4
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CeNi9Si4 的晶体结构和近藤晶格行为
DOI：
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发表时间：
2003
期刊：
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通讯作者：
G. Giester
中科院分区：
文献类型：
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作者：
H. Michor;Berger;M. El;C. Paul;E. Bauer;G. Hilscher;P. Rogl;G. Giester
研究了R=La和Ce的RNi9Si4的晶体化学、磁学、热力学和输运性质。这些化合物结晶成完全有序的四方(空间群I4/mcm)的立方NaZn13型变体。低温性质表明，CeNi9Si4具有较大的Sommerfeld值γ=155(5)mJ/molK2，而泡利顺磁LaNi9Si4的低温性质为y=33mJ/molK2。特征温度为T0≃180K的简并(J=5/2)Coqblin-Schrieffer模型很好地描述了比热和磁化率的温度依赖关系。CeNi9Si4(dCe-Ce 5.6A)中大的Ce-Ce间距意味着很弱的Ce-Ce位间交换作用，这一点得到了S(T)的证实，该结果与没有晶位间相互作用的简并Anderson晶格的理论结果非常吻合。CeNi9Si4是一个T0>；ΔCE F>>；T R K K Y的模型近藤晶格系统，其中T0、ΔC E F(晶态电场)和T R K K Y(Ruderman-Kittel-Kasuya-Yosida)分别是近藤相互作用、晶场分裂和Ce-Ce位间交换耦合的特征能标.CeNi9Si4的A/γ2=0.83(8)×10-6μΩcm(Molk/MJ)2比通常的重费米子系统的Kadowaki-Woods值小一个数量级。
We have studied the crystal chemistry and magnetic, thermodynamic, and transport properties of RNi 9 Si 4 with R=La and Ce. These compounds crystallize in a fully ordered tetragonal (space group I4/mcm) variant of the cubic NaZn 1 3 type. The low-temperature properties characterize CeNi 9 Si 4 as a Kondo lattice with a large Sommerfeld value γ=155(5) mJ/mol K 2 as compared to y=33 mJ/mol K 2 of Pauli paramagnetic LaNi 9 Si 4 . The temperature dependencies of the specific heat and susceptibility are well described by the degenerate (J =5/2) Coqblin-Schrieffer model with a characteristic temperature T 0 ≃180 K. The large Ce-Ce spacing in CeNi 9 Si 4 (d C e - C e 5.6 A) implies very weak Ce-Ce intersite exchange interactions which is corroborated by the thermoelectric power S(T) showing close agreement with theoretical results of the degenerate Anderson lattice without intersite interactions. CeNi 9 Si 4 appears to be a model type Kondo lattice system with T 0 >Δ C E F >>T R K K Y where T 0 , Δ C E F (crystalline electric field), and T R K K Y (Ruderman-Kittel-Kasuya-Yosida) are the characteristic energy scales of the Kondo interaction, crystal field splitting, and Ce-Ce intersite exchange coupling, respectively. CeNi 9 Si 4 shows a remarkably low ratio A/γ 2 =0.83 (8)×10 - 6 μΩ cm(molK/mJ) 2 which is one order-of-magnitude smaller than the usual Kadowaki-Woods ratio of heavy-fermion systems.