Boulet Pascal, de Weerd Marie-Cécile, Krnel Mitja, Vrtnik Stanislav, Jagličić Zvonko, Dolinšek Janez
Institut Jean Lamour, UMR 7198, CNRS, Université de Lorraine, Campus Artem, 2 allée André Guinier, BP 50840, 54011 Nancy Cedex, France.
J. Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
Inorg Chem. 2021 Feb 15;60(4):2526-2532. doi: 10.1021/acs.inorgchem.0c03430. Epub 2021 Feb 3.
In a search for unconventional heavy-Fermion compounds with the localized 4f moments distributed quasiperiodically instead of a conventional distribution on a regular, translationally periodic lattice, we have successfully synthesized a stable CeAuGe Tsai-type 1/1 quasicrystalline approximant of the off-stoichiometric composition CeAuGe ( = 0.17, = 0.49, = 1.08) and determined its structural model. The structure is body-centered-cubic (bcc), with space group 3̅, unit cell parameter = 14.874(3) Å, and Pearson symbol 174, and can be described as a bcc packing of partially interpenetrating multishell rhombic triacontahedral clusters. The cerium sublattice, corresponding to the magnetic sublattice, consists of a bcc packing of Ce icosahedra with an additional Ce atom in a partially occupied site (occupation 0.7) at the center of each icosahedron. The measurements of its magnetic properties and the specific heat have demonstrated that it is a regular intermetallic compound with no resemblance to heavy-Fermion systems. The partially occupied Ce2 site in the center of each Ce1 icosahedron, the mixed-occupied Au/Ge ligand sites between the Ce2 and Ce1 atoms, and the random compositional fluctuations due to nonstoichiometry of the investigated CeAuGe alloy introduce randomness into the Ce magnetic sublattice, which causes a distribution of the indirect-exchange antiferromagnetic interactions between the spins. Together with the geometric frustration of the triangularly distributed Ce moments, this leads to a spin-glass phase below the spin freezing temperature ≈ 0.28 K.
为了寻找具有非常规重费米子化合物，其局域化的4f磁矩呈准周期性分布，而非在规则的平移周期晶格上呈常规分布，我们成功合成了一种稳定的蔡氏型1/1准晶近似体CeAuGe（化学计量比偏离化学计量组成CeAuGe， = 0.17， = 0.49， = 1.08），并确定了其结构模型。该结构为体心立方（bcc），空间群为3̅，晶胞参数 = 14.874(3) Å，皮尔逊符号为174，可描述为部分相互贯穿的多壳层菱形三十面体簇的体心立方堆积。铈亚晶格对应于磁亚晶格，由Ce二十面体的体心立方堆积组成，在每个二十面体的中心有一个部分占据的位置（占据率0.7）上还有一个额外的Ce原子。对其磁性质和比热的测量表明，它是一种常规的金属间化合物，与重费米子系统毫无相似之处。每个Ce1二十面体中心的部分占据的Ce2位置、Ce原子与Ce1原子之间混合占据的Au/Ge配体位置以及所研究的CeAuGe合金由于非化学计量比导致的随机成分波动，将随机性引入到Ce磁亚晶格中，这导致了自旋之间间接交换反铁磁相互作用的分布。再加上三角形分布的Ce磁矩的几何失配，这导致在自旋冻结温度 ≈ 0.28 K以下出现自旋玻璃相。
