Effect of the A-Site Cation on Quantum Magnetism: Successive Spin-Flop Transitions in the Frustrated Magnet SrCo 2 TeO 6

We report the discovery of a new compound, SrCo 2 TeO 6, in which the CoO 6 octahedra form a double-chain structure extending along the b -axis. The structure consists of CoO 6 octahedra connected via edge-sharing in a honeycomb-like arrangement. We present a detailed investigation into the magnetic properties of the spin-1/2 system SrCo 2 TeO 6 through magnetization and specific heat measurements. Our experimental results reveal two successive long-range antiferromagnetic (AFM) phase transitions are observed at T N1 ∼ 11.6 K and T N2 ∼ 9 K, respectively, which demonstrates that SrCo 2 TeO 6 is a quantum spin system with an effective spin S eff = 1/2 and exhibits a 1/2-like magnetization plateau. Compared with the isostructural CaCo 2 TeO 6, the substitution of Sr results in a significant distortion of the Co–O–Co bond angle, which weakens the dominant antiferromagnetic exchange interaction.