Structural, optical and magnetic properties of Y-doped NiFe₂O₄ nanoparticles prepared by simple co-precipitation method

Undoped and Y-doped NiFe2O4 nanoparticles were successfully synthesized by the simple co-precipitation method without any organic gelation agent. The appropriate annealing temperature and time to obtain single-phase spinel NiFe2-xYxO4 (x = 0, 0.05, 0.1, and 0.15) is 800 degrees C for 1 h. The particle size measured from scanning electron microscope (SEM) and transmission electron microscope (TEM) images confirms the nanostructural character in the range of 20-40 nm. The crystallite size (D-XRD = 27.54-17.43 nm) decreased while the cubic lattice parameters (a = 8.2981-8.3510 angstrom) increased as the Y3+ content in nickel ferrite spinel increased. Undoped and Y-doped NiFe2O4 nanoparticles have strong optical absorption in the UV (lambda = 200-400 nm) and visible (lambda = 400-600 nm) ranges, together with significantly lower band gap energy (E-g) compared to the NiFe2O4 materials synthesized by the sol-gel and hydrothermal methods (E-g = 1.57-1.67 eV). All the undoped and Y-doped NiFe2O4 samples exhibited strong ferromagnetic behaviour with narrow magnetic hysteresis loop and high magnetization. An increase in the doped Y3+ ion in the NiFe2O4 spinel crystal lattice reduced the saturation magnetization (M-s = 84.33-28.25 emu/g) while at the same time increasing the coercivity (H-c = 69.74-23.46 Oe) and remanent magnetization of the obtained materials (M-r = 84.33-28.25 emu/g). In this manners, Y-doped NiFe2O4 nanopowders, with a narrow band gap and strong ferromagnetic behaviour, can be used as catalysts for photochemical reactions, as well as materials for transformer cores, magnetic conductors, and gas sensors.