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首页> 外文期刊>Crystal growth & design >New R3Pd5 Compounds (R = Sc, Y, Gd-Lu): Formation and Stability, Crystal Structure, and Antiferromagnetism
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New R3Pd5 Compounds (R = Sc, Y, Gd-Lu): Formation and Stability, Crystal Structure, and Antiferromagnetism

机译：新的R3Pd5化合物（R = Sc，Y，Gd-Lu）：形成与稳定性，晶体结构和反铁磁性

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The phases reported in the literature as "R2Pd3" (R = rare earth element) have been reinvestigated. The exact stoichiometric composition of this series of compounds, which form for R = Sc, Y, and from Gd to Lu, including Yb, was found to be R3Pd5. All of them crystallize in the orthorhombic Pu3Pd5 structure type (oS32-Cmcm). The crystal structure has been refined from both single crystal (for Tb3Pd5) and powder X-ray diffraction data (for Tb3Pd5, Ho3Pd5, and Tm3Pd5). These ccmpounds represent the first example of a binary phase formed by R and Pd adopting the Pu3Pd5-type featuring two crystallographic nonequivalent sites for the R atoms in the unit cell (the Wyckoff sites 4c and 8e). The variation of the lattice parameters and unit cell volume along the series strictly-follows the trend of the lanthanide contraction. An extrapolation of the volume contraction versus the R3+ ionic radius gives an atomic volume: of 29.74 angstrom(3) for Yb in the hypothetical trivalent metallic state (under normal conditions). The formation temperatures and mechanisms, peritectic reaction, and stability ranges have also been investigated. It turns out that Gd3Pd5 is a high temperature phase; it was not possible to quench this compound as a metastable phase, at room temperature, to be measured. In the light Of our results, most of the R-Pd phase diagrams need to be revised. The magnetization, heat capacity,, and electrical resistivity have been Measured for Tb3Pd5, Dy3Pd5, Ho3Pd5, and Er3Pd5. They order antiferromagnetically at low temperatures, each undergoing two transitions, T-N1 and T-N2 (with T-N1, going from 13.5 to 5.1 K and T-N2 going from 6.5 to 3.6 K, respectively for Tb and Ho compounds). From our data we cannot distinguish: whether the two rare earth sublattices sequentially order magnetically at T-N1 and T-N2, respectively, or whether they are simultaneously involved in both transitions. The electronic structure calculations predict antiferromagnetic ordering also for Gd3Pd5. Y(3)Ed(5) is a Pauli paramagnet.
机译：文献中报告为“ R2Pd3”的相（R =稀土元素）已被重新研究。发现该系列化合物的精确化学计量组成为R 3 Pd 5，其中R = Sc，Y且从Gd到Lu，包括Yb。它们全部以正交Pu3Pd5结构类型（oS32-Cmcm）结晶。晶体结构已经从单晶（对于Tb3Pd5）和粉末X射线衍射数据（对于Tb3Pd5，Ho3Pd5和Tm3Pd5）中得到改善。这些化合物代表R和Pd采用Pu3Pd5-型形成的二元相的第一个例子，Pu3Pd5-型的特征是晶胞中R原子的两个晶体学非等价位点（Wyckoff位点4c和8e）。晶格参数和晶胞体积沿该序列的变化严格遵循镧系元素的收缩趋势。相对于R3 +离子半径的体积收缩推断得出原子体积：在假定的三价金属态（正常条件下）下，Yb的原子体积为29.74埃（3）。还研究了地层温度和机理，包晶反应和稳定性范围。事实证明，Gd3Pd5是高温相。在室温下，不可能将该化合物淬灭为亚稳相。根据我们的结果，大多数R-Pd相图都需要修改。已针对Tb3Pd5，Dy3Pd5，Ho3Pd5和Er3Pd5测量了磁化强度，热容量和电阻率。它们在低温下反铁磁排列，每个经历两个跃迁，T-N1和T-N2（T-N1分别从Tb和Ho化合物从13.5降低到5.1 K，T-N2分别从6.5改变到3.6 K）。从我们的数据中，我们无法区分：两个稀土亚晶格分别在T-N1和T-N2处依序磁性排序，或者它们是否同时参与两个跃迁。电子结构计算也预测Gd3Pd5的反铁磁有序性。 Y（3）Ed（5）是保利（Pauli）永磁体。

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