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Crystal structure and physical properties of Yb2In and Eu2−xYbxIn alloys
Physical Review Materials ( IF 3.1 ) Pub Date : 
F. Guillou, H. Yibole, R. Hamane, V. Hardy, Y. B. Sun, J. J. Zhao, Y. Mudryk, V. K. Pecharsky

While binary RE2In, 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 Eu2In calls for further exploration of structures and properties of RE2In, in particular for the least documented RE = Eu and Yb cases. Here, we investigate Eu2xYbxIn 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 Yb2In), magnetization (5 - 300 K), as well as resistivity (5 - 300 K) and calorimetric (2 - 150 K) measurements for Yb2In. 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 Yb2In, at least between 100 and 375 K, which is in line with the absence of 4f magnetism. In agreement with XRD and magnetization data, the resistivity of Yb2In is rather featureless and typical of a metal. Establishing Yb2In as a nonmagnetic iso-structural reference for Eu2In 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 mol1 K1 at T= 100 K) is concentrated in a 3 K temperature window around the TC of Eu2In. Starting from the ferromagnetic compound Eu2In ($T_{C\thinspace }=$ 55.2(5) K), we show that Yb substitutions in Eu2xYbxIn lead to a decrease in both the Curie temperature (TC= 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$^{\mathrm{-1\thinspace }}$K1 for ΔB= 2 T is found at 44 K in Eu1.75Yb0.25In, demonstrating that the giant magnetocaloric effect of Eu2In can be tuned to lower temperatures by Yb substitutions.

中文翻译:

Yb2In和Eu2-xYbxIn合金的晶体结构和物理性能

而二进制RE2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-XbX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)2In),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2In,至少介于100和375 K之间,这与不存在4F磁性。与XRD和磁化数据一致,Yb的电阻率2In相当无特色,是典型的金属。建立Yb2In作为Eu的非磁性同构参考2In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-1个 ķ-1个Ť= 100 K)集中在3 K温度范围内 ŤC 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-XbX导致居里温度(ŤC= 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-1个 对于 Δ= 在欧盟的44 K处发现2 T1.75b0.25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。
更新日期:2020-09-11
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