BaLnMnTe (Ln = Pr, Gd, and Yb; x = Ln vacancy): syntheses, crystal structures, optical, resistivity, and electronic structure.

Three new isostructural quaternary tellurides, BaLnMnTe (Ln = Pr, Gd, and Yb), have been synthesized by the molten-flux method at 1273 K. The single-crystal X-ray diffraction studies at 298(2) K showed that BaLnMnTe crystallize in the space group -C2/m of the monoclinic crystal system. There are six unique crystallographic sites in this structure's asymmetric unit: one Ba site, one Ln site, one Mn site, and three Te sites. The Ln site in the BaLnMnTe structure is partially filled, which leaves about one-third of the Ln sites vacant (□) for Pr and Gd compounds. These structures do not contain any homoatomic or metallic bonding and can be charge-balanced as (Ba)(Gd/Pr)(Mn)(Te). The refined composition for the Yb compound is BaYbMnTe and can be charge-balanced with a mixed valence state of Yb/Yb. The crystal structures of BaLnMnTe consist of complex layers of [LnMnTe] stacked along the [100] direction, with Ba cations separating these layers. The Ln atoms are bound to six Te atoms that form a distorted octahedral geometry around the central Ln atom. Each Mn atom in this structure is coordinated to four Te atoms in a distorted tetrahedral fashion. These LnTe and MnTe units are the main building blocks of the BaLnMnTe structure. The optical absorption study performed on a polycrystalline BaGdMnTe sample reveals a direct bandgap of 1.06(2) eV consistent with the DFT study. A semiconducting behavior was also observed for polycrystalline BaGdMnTe from the resistivity study. The temperature-dependent magnetic studies on a polycrystalline sample of BaGdMnTe did not reveal any long-range magnetic order down to 5 K. The effective magnetic moment (μ) of 10.37μ calculated using the Curie-Weiss law is in good agreement with the theoretical value (μ) of 10.58μ.