Synthesis and Self-Assembly of Nickel-Substituted Ferrite Nanoparticles with Controlled Morphology and Chemical Composition

Nickel ferrite is a highly promising material that has potential for various applications in spintronics, electromagnetic devices, and sensors. In this study, we successfully synthesized Ni x Fe 3– x O 4 nanoparticles with a cubic inverse spinel structure using a facile solvothermal method. By controlling the molar ratio of precursors, the morphology of the nanoparticles transformed from cubes to octahedra as the x value increased from 0 to 1. Additionally, the lattice constant exhibited a slight decrease from 8.382 to 8.344 Å due to the smaller ionic radii of Ni 2+ compared to Fe 2+ . The obtained hysteresis loop and ZFC/FC curves revealed decreases in saturation magnetization and blocking temperature as the x value increased, which could be attributed to the smaller magnetic moment of Ni 2+ compared to Fe 2+ . Based on the excellent dispersion and uniform size of octahedral NiFe 2 O 4 nanoparticles, microscale self-assembled arrays were obtained. The number of layers was adjusted by varying the concentration of the NiFe 2 O 4 suspension. Monolayer, bilayer, and trilayer self-assembled arrays are exhibited and different structures are explored. The self-assembled NiFe 2 O 4 nanoparticles make a significant step forward in the bottom-up approach to fabricating micro-/nano-functional devices, applicable in areas such as nanosensors, spintronics, and nanoelectronics.