Zigzag magnetic order in a novel tellurate compound Na4−δNiTeO6 with S = 1 chains.

Na_4−δNiTeO₆ is a rare example in the transition-metal tellurate family of realizing an S = 1 spin-chain structure. By performing neutron powder diffraction measurements, the ground-state magnetic structure of Na_4−δNiTeO₆ is determined. These measurements reveal that below T_N ∼ 6.8(2) K, the Ni²⁺ moments form a screwed ferromagnetic (FM) spin-chain structure running along the crystallographic a axis but these FM spin chains are coupled antiferromagnetically along the b and c directions, giving rise to a magnetic propagation vector of k = (0, 1/2, 1/2). This zigzag magnetic order is well supported by first-principles calculations. The moment size of Ni²⁺ spins is determined to be 2.1(1)μ_B at 3 K, suggesting a significant quenching of the orbital moment due to the crystalline electric field (CEF) effect. The previously reported metamagnetic transition near H_C ∼ 0.1 T can be understood as a field-induced spin-flip transition. The relatively easy tunability of the dimensionality of its magnetism by external parameters makes Na_4−δNiTeO₆ a promising candidate for further exploring various types of novel spin-chain physics. [ABSTRACT FROM AUTHOR]