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Solid solutions EuAu4Cd2−xMgx with a remarkably stable ferromagnetic ground state
Zeitschrift für Naturforschung B ( IF 0.8 ) Pub Date : 2020-08-27 , DOI: 10.1515/znb-2020-0066
Maximilian K. Reimann 1 , Judith Bönnighausen 1 , Steffen Klenner 1 , Rainer Pöttgen 1
Affiliation  

Abstract Samples of the solid solutions EuAu4Cd2−x Mg x were synthesized from the elements in sealed tantalum ampoules. The elements were reacted at a maximum temperature of 1273 K followed by slow cooling. For crystal growth, the polycrystalline samples were ground to powders, pressed to pellets and annealed again. All samples crystallize with the tetragonal YbAl4Mo2-type structure, space group I4/mmm. The solid solution extends up to x = 1 and the Cd/Mg substitution has only a minor influence on the lattice parameters. The samples have been characterized by powder X-ray diffraction and the structure of EuAu4Cd1.58(2)Mg0.42(2) was refined from single crystal X-ray diffractometer data: a = 715.46(14), c = 549.96(11) pm, wR2 = 0.0334, 180 F 2 values and 11 variables. The striking crystal chemical motifs of the EuAu4Cd2−x Mg x structures are Eu@Au12 and (Cd/Mg)@Au8(Cd/Mg)2 polyhedra and linear Cd/Mg chains in form of a tetragonal rod packing with distances of 275 pm for Cd/Mg–Cd/Mg. Temperature dependent magnetic susceptibility measurements of all samples from the solid solutions EuAu4Cd2−x Mg x revealed Curie–Weiss behavior and stable divalent europium. All samples are ordered ferromagnetically around T = 16 K, and magnetization isotherms at 3 K classify these materials as soft ferromagnets. It is remarkable that the structural Cd/Mg disorder within the chains does not influence the ferromagnetic ground state. The divalent nature of europium in these intermetallics was exemplarily studied for the EuAu4Cd1.4Mg0.6 sample by 151Eu Mössbauer spectroscopy. At 6 K the isomer shift is −9.95(4) mm s−1 and one observes full magnetic hyperfine field splitting with B hf = 27.1(1) T.

中文翻译:

具有非常稳定的铁磁基态的固溶体 EuAu4Cd2−xMgx

摘要 EuAu4Cd2-x Mg x 固溶体样品由密封钽安瓿中的元素合成。这些元素在最高温度 1273 K 下反应,然后缓慢冷却。对于晶体生长,将多晶样品研磨成粉末,压成颗粒并再次退火。所有样品均以四方 YbAl4Mo2 型结构结晶,空间群为 I4/mmm。固溶体扩展到 x = 1,Cd/Mg 取代对晶格参数的影响很小。样品已通过粉末 X 射线衍射表征,从单晶 X 射线衍射仪数据中提炼出 EuAu4Cd1.58(2)Mg0.42(2) 的结构:a = 715.46(14), c = 549.96(11 ) pm, wR2 = 0.0334, 180 F 2 值和 11 个变量。EuAu4Cd2−x Mg x 结构的显着晶体化学基序是 Eu@Au12 和 (Cd/Mg)@Au8(Cd/Mg)2 多面体和线性 Cd/Mg 链,呈四方棒堆积形式,距离为 275 pm对于 Cd/Mg-Cd/Mg。来自固溶体 EuAu4Cd2-x Mg x 的所有样品的温度相关磁化率测量揭示了居里-魏斯行为和稳定的二价铕。所有样品都在 T = 16 K 附近铁磁排列,3 K 处的磁化等温线将这些材料归类为软铁磁体。值得注意的是,链内的结构 Cd/Mg 无序不影响铁磁基态。通过 151Eu Mössbauer 光谱法,对 EuAu4Cd1.4Mg0.6 样品的这些金属间化合物中铕的二价性质进行了示例性研究。在 6 K 时,异构体位移为 -9。
更新日期:2020-08-27
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