Synthesis, structures and magnetic properties of the Eu-based quaternary tellurides EuGdCuTe3 and EuLuCuTe3

Novel heterometallic quaternary tellurides EuGdCuTe₃ and EuLuCuTe₃ are reported for the first time. Both compounds were obtained from the elements as single crystals using the flux-assisted synthetic approach. The crystal structure of EuGdCuTe₃ was solved in orthorhombic space group Pnma with the structural type Eu₂CuS₃, while the crystal structure of EuLuCuTe₃ belongs to orthorhombic space group Cmcm with the structural type KZrCuS₃. The 3D crystal structure of EuGdCuTe₃ is constructed from EuTe₇ capped trigonal prisms, GdTe₆ distorted octahedra as well as CuTe₄ tetrahedra. The octahedra form 2D layers, further strengthened by 1D polymeric chains (CuTe₄)_n. These layers are separated by 1D dimeric ribbons, formed by EuTe₇ capped trigonal prisms and 1D free channels. The 3D crystal structure of EuLuCuTe₃ is constructed from EuTe₆ trigonal prisms, LuTe₆ distorted octahedra and CuTe₄ tetrahedra. The latter two polyhedra also form 2D layers, which are separated by alternating 1D polymeric chains (EuTe₆)_n and 1D free channels. Both tellurides were found to be paramagnetic with the transition to a ferrimagnetic state at about 8 K for EuGdCuTe₃ and to a ferromagnetic state at about 3 K for EuLuCuTe₃.