Synthesis and magnetic properties of new tellurate compounds NaMTeO (M = Co and Ni) with a ferromagnetic spin-chain structure.

New tellurate compounds NaMTeO (M = Co and Ni) were synthesized by a conventional high-temperature solid-state reaction. The title compounds crystallize in the monoclinic system of a space group P2/c and the triclinic system of a space group P1[combining macron], respectively. Both compounds exhibit a zigzag spin-chain structure, in which NaCoTeO shows uniform chains built by Co ions and NaNiTeO shows alternating chains built by Ni ions. Magnetic measurements confirm that NaCoTeO and NaNiTeO possess an antiferromagnetic ordering at T = ∼3 K and ∼6.5 K, respectively, while a metamagnetic transition can be observed in the magnetization curve with an increasing field at 2 K.