While binary RE${}_2$In, where RE $=$ rare-earth, have been reported a few decades ago, recent investigations revealed intriguing new physical insights. For instance, the discovery of a nearly ideal first-order ferromagnetic transition in Eu${}_2$In calls for further exploration of structures and properties of RE${}_2$In, in particular for the least documented RE $=$ Eu and Yb cases. Here, we investigate Eu${}_{{2-}_x}$Yb${}_x$In pseudo-binaries with nominal values of $x=$ 0.25, 0.5, 0.75, 1, 1.5, 2, by powder x-ray diffraction (including as function of temperature from 100 to 375 K for Yb${}_2$In), magnetization (5 - 300 K), as well as resistivity (5 - 300 K) and calorimetric (2 - 150 K) measurements for Yb${}_2$In. Compared to other RE, Yb or Eu always raise challenging questions linked to their valence states. From average atomic volume, Yb is anticipated to be divalent in Yb${}_2$In, at least between 100 and 375 K, which is in line with the absence of 4$f$ magnetism. In agreement with XRD and magnetization data, the resistivity of Yb${}_2$In is rather featureless and typical of a metal. Establishing Yb${}_2$In as a nonmagnetic iso-structural reference for Eu${}_2$In allows one to use its heat capacity to revisit that of the latter, and get experimental insights into the exceptional magnetocaloric effect of the compound with Eu. In particular, we show that a third of the total magnetic entropy ($S_{m} $ 35.6 J mol${}^{-1}$ K${}^{-1}$ at $T=$ 100 K) is concentrated in a 3 K temperature window around the $T_C$ of Eu${}_2$In. Starting from the ferromagnetic compound Eu${}_2$In ($T_{C\thinspace }=$ 55.2(5) K), we show that Yb substitutions in Eu${}_{{2-}_x}$Yb${}_x$In lead to a decrease in both the Curie temperature ($T_C=$ 41(2) and 32(2) K for $x=$ 0.25 and 0.5) and magnetic saturation, while weakening the first-order character of the transition as $x$ increases. A significant isothermal entropy change of 5.1(4) J mol$^{\mathrm{-1\thinspace }}$K${}^{-1}$ for $\Delta B=$ 2 T is found at 44 K in Eu${}_{1.75}$Yb${}_{0.25}$In, demonstrating that the giant magnetocaloric effect of Eu${}_2$In can be tuned to lower temperatures by Yb substitutions.

中文翻译：

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Yb2In和Eu2-xYbxIn合金的晶体结构和物理性能

而二进制RE${}_2$在哪里，RE $=$稀土，几十年前已有报道，最近的调查显示出有趣的新物理见解。例如，在Eu中发现了近乎理想的一阶铁磁跃迁${}_2$呼吁进一步探索稀土的结构和性质${}_2$尤其是对于文件最少的RE $=$Eu和Yb案件。在这里，我们调查欧盟${}_{{2-}_X}$b${}_X$在标称值为的伪二进制文件中 $X=$ 0.25、0.5、0.75、1、1.5、2，通过粉末X射线衍射（包括Yb在100至375 K之间的温度函数）${}_2$In），Yb的磁化强度（5-300 K）以及电阻率（5-300 K）和量热法（2-150 K）${}_2$在。与其他RE相比，Yb或Eu总是提出与其价态相关的具有挑战性的问题。从平均原子量来看，预计Yb在Yb中是二价的${}_2$In，至少介于100和375 K之间，这与不存在4$F$磁性。与XRD和磁化数据一致，Yb的电阻率${}_2$In相当无特色，是典型的金属。建立Yb${}_2$In作为Eu的非磁性同构参考${}_2$In允许人们利用其热容量重新获得后者的热容量，并获得有关该化合物与Eu的优异磁热效应的实验见解。特别地，我们表明总磁熵的三分之一（$ S_ {m} $ 35.6 J mol${}^{-\mathrm{1个}}$ ķ${}^{-\mathrm{1个}}$ 在 $Ť=$ 100 K）集中在3 K温度范围内 ${Ť}_C$ 欧盟${}_2$在。从铁磁化合物Eu开始${}_2$在（$ T_ {C \ thinspace} = $ 55.2（5）K）中，我们证明了Eu中的Yb替代${}_{{2-}_X}$b${}_X$导致居里温度（${Ť}_C=$ 41（2）和32（2）K $X=$ 0.25和0.5）和磁饱和，同时削弱了过渡的一阶特性，如 $X$增加。5.1（4）J mol $ ^ {\ mathrm {-1 \ thinspace}} $ K的显着等温熵变化${}^{-\mathrm{1个}}$ 对于 $\Delta 乙=$ 在欧盟的44 K处发现2 T${}_{1.75}$b${}_{0.25}$在，证明了Eu的巨大磁热效应${}_2$可通过Yb取代将In调节至较低的温度。