Quasiquartet crystal-electric-field ground state with possible quadrupolar ordering in the tetragonal compound YbRu2Ge2
Quasiquartet crystal-electric-field ground state with possible quadrupolar ordering in the tetragonal compound YbRu2Ge2
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四方化合物 YbRu2Ge2 中具有可能的四极有序性的准四方晶体电场基态
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
C. Geibel
中科院分区：
文献类型：
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作者：
H. Jeevan;Z. Hossain;C. Geibel
我们通过对通量生长的单晶进行磁化率 $\chi$(T)、比热 C(T) 和电阻率 $\rho$(T) 测量，研究了 YbRu$_{2}$Ge$_{2}$ 的磁性。 $\chi$(T)沿易平面的居里-韦斯行为、低温下较大的磁熵以及$\rho$(T)的弱近藤样增加证明了稳定的三价Yb态。 T$_{0}$ = 10.2 K、T$_{1}$ = 6.5 K 和 T$_{2}$ = 5.7 K 处的 C(T)、$\rho$(T) 和 $\chi$(T) 异常现象证明了复杂的有序现象，T$_{0}$ 大于迄今为止发现的最高 Yb 磁有序温度。 T$_{0}$ 上方的磁熵几乎达到 Rln4，表明晶体电场 (CEF) 基态是准四重态，而不是预期的双重态。 T$_{0}$ 处的行为相当不寻常，表明这种转变与四极有序有关，是 CEF 准四重基态的结果。准四重 CEF 基态、高有序温度和四极相互作用的相关性相结合，使得 YbRu$_{2}$Ge$_{2}$ 成为 Yb 基化合物中相当独特的系统。
e have investigated the magnetic properties of YbRu$_{2}$Ge$_{2}$ by means of magnetic susceptibility $\chi$(T), specific heat C(T) and electrical resistivity $\rho$(T) measurements performed on flux grown single crystals. The Curie-Weiss behavior of $\chi$(T) along the easy plane, the large magnetic entropy at low temperatures and the weak Kondo like increase in $\rho$(T) proves a stable trivalent Yb state. Anomalies in C(T), $\rho$(T) and $\chi$(T) at T$_{0}$ = 10.2 K, T$_{1}$ = 6.5 K and T$_{2}$ = 5.7 K evidence complex ordering phenomena, T$_{0}$ being larger than the highest Yb magnetic ordering temperature found up to now. The magnetic entropy just above T$_{0}$ amounts to almost Rln4, indicating that the crystal electric field (CEF) ground state is a quasiquartet instead of the expected doublet. The behavior at T$_{0}$ is rather unusual and suggest that this transition is related to quadrupolar ordering, being a consequence of the CEF quasiquartet ground state. The combination of a quasiquartet CEF ground state, a high ordering temperature, and the relevance of quadrupolar interactions makes YbRu$_{2}$Ge$_{2}$ a rather unique system among Yb based compounds.