PbMn(IV)TeO6: A New Noncentrosymmetric Layered Honeycomb Magnetic Oxide.

PbMnTeO6, a new noncentrosymmetric layered magnetic oxide was synthesized and characterized. The crystal structure is hexagonal, with space group P62m (No. 189), and consists of edge-sharing (Mn4+/Te6+)O6 trigonal prisms that form honeycomb-like two-dimensional layers with Pb2+ ions between the layers. The structural difference between PbMnTeO6, with disordered/trigonal prisms of Mn4+/Te6+, versus the similar chiral SrGeTeO6 (space group P312), with long-range order of Ge4+ and Te6+ in octahedral coordination, is attributed to a difference in the electronic effects of Ge4+ and Mn4+. Temperature-dependent second harmonic generation by PbMnTeO6 confirmed the noncentrosymmetric character between 12 and 873 K. Magnetic measurements indicated antiferromagnetic order at TN ≈ 20 K and a frustration parameter (|θ|/TN) of ∼2.16.