Crystal structure and physical properties of indium flux grown RE₂AuSi₃ (RE = Eu, Yb)

Abstract

Two new intermetallic compounds Eu₂AuSi₃ and Yb₂AuSi₃ having prismatic and rod like shapes, respectively, were grown using indium as inert metal flux. The crystal structure of both compounds was refined using X-ray diffraction data on selected single crystals. Both compounds are ordered variants of the AlB₂ structure type and crystallize in the orthorhombic system. Eu₂AuSi₃ adopts the Ca₂AgSi₃ structure type, Fmmm space group and lattice parameters a = 8.3060(17) Å, b = 9.0369(18) Å, c = 14.377(3) Å. Yb₂AuSi₃, on the other hand, crystallizes in the Ba₂LiSi₃ structure type, Fddd space group and lattice parameters a = 8.2003(16) Å, b = 14.187(3) Å, c = 16.869(3) Å. Both Eu₂AuSi₃ and Yb₂AuSi₃ consist of two dimensional hexagonal units built up of [Au₃Si₃] mixed sites and the europium atoms are sandwiched between two adjacent hexagonal layers. Magnetic measurements suggest both compounds have divalent rare earth atoms. The temperature dependent magnetic susceptibility data of Eu₂AuSi₃ suggests the Curie–Weiss behavior above 30 K and an antiferromagnetic ordering around 26 K. Yb₂AuSi₃ is diamagnetic in the higher temperature range (>175 K) and is weakly paramagnetic below 100 K indicating a probable valence fluctuation in Yb.