Syntheses and Magnetic Properties of New Tellurite–Sulfate Compounds M₂(TeO₃)(SO₄)·H₂O (M = Co, Mn) with a Layer Structure Showing a Distorted Honeycomb Spin–Lattice

New tellurite–sulfate compounds M₂(TeO₃)­(SO₄)·H₂O (M = Co, Mn) are synthesized by a conventional hydrothermal method. Two compounds are found to exhibit a similar structure, which both crystallize in the orthorhombic system of space group <i>Pbcm</i>. Te⁴⁺ ions are coordinated by three O atoms, forming a quite distorted TeO₃ trigonal pyramid with lone-pair electrons, while magnetic Co²⁺ or Mn²⁺ ions construct a wavelike layer with a distorted honeycomb spin–lattice. Magnetic measurements confirm that two isostructural compounds display different magnetic behaviors, in which Co₂(TeO₃)­(SO₄)·H₂O shows a canted antiferromagnetic ordering at ∼15 K, while Mn₂(TeO₃)­(SO₄)·H₂O shows a collinear antiferromagnetic ordering at ∼28 K. The nature of different magnetic behaviors between two isostructural compounds is also discussed