Synthesis and magnetic properties of MNb2O6 (M = Fe, Co, Ni) nanoparticles

Abstract

Considerable efforts have been exerted on the controllable synthesis of columbite niobate ceramics due to their fascinating properties and applications. Especially, it is still a great challenge to fabricate nanostructures of the niobate series. In this research, FeNb₂O₆, CoNb₂O₆ and NiNb₂O₆ nanoparticles have been successfully prepared via a facile hydrothermal route followed by heat treatment. X-ray powder diffraction patterns show that all the products have the typical orthorhombic columbite structure. The electron microscopy analyses reveal that the obtained nanoparticles have diameters of 50–100 nm. The magnetic property results demonstrate that the magnetically ordered state is hard to observe down to 1.8 K for the FeNb₂O₆ sample, while the magnetic transition temperatures of T_N = 3 K and T_N = 6 K can be obtained for CoNb₂O₆ and NiNb₂O₆ samples, respectively. A weak ferromagnetic moment can be detected below 5 K for both CoNb₂O₆ and NiNb₂O₆ samples. Furthermore, the NiNb₂O₆ sample even exhibits a metamagnetic transition at 1.8 K due to the spin flipping of the ferromagnetic chains.