| Autor: |
Panigrahi G; Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502285, India. jaiprakash@chy.iith.ac.in., Jana S, Ishtiyak M, Narayanswamy S, Bhattacharjee PP, Ramanujachary KV, Niranjan MK, Prakash J |
| Jazyk: |
angličtina |
| Zdroj: |
Dalton transactions (Cambridge, England : 2003) [Dalton Trans] 2021 May 21; Vol. 50 (19), pp. 6688-6701. Date of Electronic Publication: 2021 Apr 28. |
| DOI: |
10.1039/d1dt00057h |
| Abstrakt: |
Three new isostructural quaternary tellurides, Ba 2 Ln 1-x Mn 2 Te 5 (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 Ba 2 Ln 1-x Mn 2 Te 5 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 Ba 2 Ln 1-x Mn 2 Te 5 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 2+ ) 2 (Gd/Pr 3+ ) 2/3 (Mn 2+ ) 2 (Te 2- ) 5 . The refined composition for the Yb compound is Ba 2 Yb 0.74(1) Mn 2 Te 5 and can be charge-balanced with a mixed valence state of Yb 2+ /Yb 3+ . The crystal structures of Ba 2 Ln 1-x Mn 2 Te 5 consist of complex layers of [Ln 1-x Mn 2 Te 5 ] 4- stacked along the [100] direction, with Ba 2+ 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 6 and MnTe 4 units are the main building blocks of the Ba 2 Ln 1-x Mn 2 Te 5 structure. The optical absorption study performed on a polycrystalline Ba 2 Gd 2/3 Mn 2 Te 5 sample reveals a direct bandgap of 1.06(2) eV consistent with the DFT study. A semiconducting behavior was also observed for polycrystalline Ba 2 Gd 2/3 Mn 2 Te 5 from the resistivity study. The temperature-dependent magnetic studies on a polycrystalline sample of Ba 2 Gd 2/3 Mn 2 Te 5 did not reveal any long-range magnetic order down to 5 K. The effective magnetic moment (μ eff ) of 10.37μ B calculated using the Curie-Weiss law is in good agreement with the theoretical value (μ cal ) of 10.58μ B . |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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