Spin-Flop Transition in a Nickel-Octacyanidotungstate Chain Magnet

Crystal engineering of molecular magnetic materials often leads to novel magnetic functionalities. In this study, we synthesized an ionic chain magnet, i.e., [Ni-II(imi)(6)]{[Ni-II(imi)(4)]-[WV(CN)(8)]}2.4H(2)O (imi = imidazole; NiW) comprising anionic cyanido-bridged [Ni-II(imi)(4)WV(CN)(8)](n)(n-) chains and cationic mononuclear [NiII(imi)(6)](2+) complexes. Ferromagnetic coupling between NiII and WV with S = 1 and 1/2, respectively, via a bridging cyanido ligand is found within the chain. However, the total magnetization of NiW is canceled out by a notable antiferromagnetic interchain interaction below a Neel temperature of 8.5 K. Such an antiferromagnetic interaction can be overcome by applying an external magnetic field of 0.9 T at 2 K, and a steep spin-flop transition is observed. From a crystal engineering perspective, we attribute this metamagnetic behavior to the isolated [NiII(imi)(6)](2+) complex that attracts the chains to be close to each other. Additionally, the complex operates as an independent paramagnetic spin source that offers an extra magnetization state of this compound.