Negative Magnetization Effect in Distorted Honeycomb Ni<inf>4</inf>Nb<inf>2</inf>O<inf>9</inf> Ceramics

Negative magnetization effect in the quasi-two-dimensional distorted honeycomb-layered Ni4Nb2O9 ceramics is revealed through rigorous magnetic measurements. Owing to the different degrees of distortion, the Ni–Ni honeycomb layers with antiferromagnetic interlayered coupling demonstrate two types of temperature dependences, resulting in a negative magnetization effect. Here we report the structure, magnetism, magnetic switching effect and magnetocaloric effect in Ni4Nb2O9 compound, synthesized by the solid-state reaction method. The magnetization curves display a ferrimagnetic behavior with a critical temperature of 76 K. The negative magnetization state occurs at 32 K which can be ascribed to the different temperature dependence of two distorted honeycomb layers. Besides, the tunable magnetic switching effect can be obtained by changing the temperature or magnitude of the external field that shows the potential application prospects. These results provide a new platform and understanding of the negative magnetization effect in these series of materials which consist of antiferromagnetic coupling sublattices.