CeRu $_2$ As $_2$和CeIr $_2$ As $_2$的合成和物理性能
Synthesis and physical properties of CeRu$_2$As$_2$ and CeIr$_2$As$_2$
摘要：
通过电输运、磁性和热力学测量，研究了CeRu $_2$ As $_2$和CeIr $_2$ As $_2$的物理性质.它们分别为ThCr $_2$ Si $_2$型和CaBe $_2$ Ge $_2$型晶体结构。CeRu $_2$ As $_2$在低于$T_N$ =4.3 K时显示出局域化的长程反铁磁有序，具有中等的电子索末菲系数$γ_0$ =35 mJ/mol $\cdot$ K $^2$。在低于$T_N$ 2 T附近观察到场致变磁转变。取向CeRu $_2$的磁化率测量作为$_2$粉末表明，它有一个易磁化轴，铈力矩沿$\mathbf{c}$轴单轴排列。相比之下，CeIr $_2$ As $_2$是具有增强的$γ_0$ $>$ 300 mJ/mol $\cdot$ K $^2$的磁性无序重费米子金属。两种化合物的起始近藤温度分别为6 K和30 K。讨论了晶体结构对近藤耦合强度的影响。本工作为进一步研究电子关联、量子临界性和重电子效应提供了两种新的致密近藤晶格材料。
英文摘要：
We studied the physical properties of two Kondo-lattice compounds, CeRu$_2$As$_2$ and CeIr$_2$As$_2$, by a combination of electric transport, magnetic and thermodynamic measurements. They are of ThCr$_2$Si$_2$-type and CaBe$_2$Ge$_2$-type crystalline structures, respectively. CeRu$_2$As$_2$ shows localized long-range antiferromagnetic ordering below $T_N$=4.3 K, with a moderate electronic Sommerfeld coefficient $γ_0$=35 mJ/mol$\cdot$K$^2$. A field-induced metamagnetic transition is observed near 2 T below $T_N$. Magnetic susceptibility measurements on aligned CeRu$_2$As$_2$ powders suggest that it has an easy axis and that the cerium moments align uniaxially along $\mathbf{c}$ axis. In contrast, CeIr$_2$As$_2$ is a magnetically nonordered heavy-fermion metal with enhanced $γ_0$$>$300 mJ/mol$\cdot$K$^2$. The initial onset Kondo temperatures of the two compounds are respectively 6 K and 30 K. We discuss the role of the crystal structure to the strength of Kondo coupling. This work provides two new dense Kondo-lattice materials for further investigations on electronic correlation, quantum criticality and heavy-electron effects.
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