Structural phase transitions in a new compound Eu₂AgGe₃

Abstract

A new intermetallic compound Eu₂AgGe₃ has been synthesized using high-frequency induction heating method. Single-crystal X-ray diffraction data showed that Eu₂AgGe₃ crystallizes in the orthorhombic Ba₂LiSi₃ structure type, with Fddd space group and lattice parameters a = 8.7069(17) Å, b = 15.011(3) Å, c = 17.761(4) Å. Eu₂AgGe₃ is composed of infinite arrays of hexagonal [Ag₃Ge₃] units stacked along the [001] direction, and the Eu sites are sandwiched between these parallel hexagonal networks. Temperature-dependent powder XRD data and DTA hint toward a structural phase transition from orthorhombic to hexagonal above 477 K and an unusual reversible transition to the original phase, i.e., orthorhombic phase at around 718 K. Magnetic measurements on Eu₂AgGe₃ sample show paramagnetic behavior above 100 K and weak ferromagnetic interactions below 80 K. Mössbauer spectroscopy and X-ray absorption near-edge spectroscopic (XANES) studies reveal that Eu atoms in Eu₂AgGe₃ exist in the divalent oxidation state.