Structure and Magnetic Behavior of Layered Honeycomb Tellurates, BiM(III)TeO 6 (M = Cr, Mn, Fe).

New layered honeycomb tellurates, BiM(III)TeO ₆ (M = Cr, Mn, Fe) were synthesized and characterized. BiM(III)TeO ₆ (M = Cr, Fe) species crystallize in a trigonal space group, P3̅1c (No. 163), of edge-sharing M ³⁺ /Te ⁶⁺ O ₆ octahedra, which form honeycomb-like double layers in the ab plane with Bi ³⁺ cations located between the layers. Interestingly, the structure of BiMnTeO ₆ is similar to those of the Cr/Fe analogues, but with monoclinic space group, P2 ₁ /c (No. 14), attributed to the strong Jahn-Teller distortion of Mn ³⁺ cations. The crystal structure of BiM(III)TeO ₆ is a superstructure of PbSb ₂ O ₆ -related materials (ABB'O ₆ ). The Cr ³⁺ and Fe ³⁺ cations are ordered 80% and 90%, respectively, while the Mn ³⁺ ions are completely ordered on the B-site of the ABB'O ₆ structure. BiCrTeO ₆ shows a broad antiferromagnetic transition (AFM) at ∼17 K with a Weiss temperature (θ) of -59.85 K, while BiFeTeO ₆ and BiMnTeO ₆ show sharp AFM transitions at ∼11 K with θ of -27.56 K and at ∼9.5 K with θ of -17.57 K, respectively. These differences in the magnetic behavior are ascribed to the different concentration of magnetic nearest versus next-nearest neighbor interactions of magnetic cations due to the relative differences in the extent of M/Te ordering.