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.

Automated summary

Crystal engineering has led to the synthesis of a new ionic chain magnet, NiW, which contains anionic cyanido-bridged chains and cationic mononuclear complexes. The compound exhibits ferromagnetic coupling within the chain but antiferromagnetic interaction between chains. This antiferromagnetic interaction can be overcome by applying an external magnetic field, resulting in a spin-flop transition. The unique metamagnetic behavior is attributed to the interaction between the complexes and chains.