Synthesis and Characterization of Samarium-Doped Nickel-Cobalt Ferrite Nanoparticles for Advanced Magnetic Applications

Nanoparticles of samarium-doped nickel-cobalt ferrites with the formula Ni₀.₇Co₀.₃Fe₂₋ₓSmₓO₄ (x = 0.00 and 0.015) were successfully synthesized using the citrate gel auto-combustion method. X-ray diffraction analysis confirmed the formation of a pure cubic spinel phase, with a slight reduction in lattice constant from 8.3502 Å to 8.3319 Å as samarium content increased, indicating the substitution of Sm³⁺ ions into the spinel lattice. The crystallite size decreased from approximately 35.2 nm for the undoped sample to 23.5 nm for the doped sample, reflecting the influence of samarium on grain growth. Field Emission Scanning Electron Microscopy revealed spherical particles with some agglomeration, typical of chemically synthesized ferrite nanoparticles. Magnetic studies showed a modest decrease in saturation magnetization from 30.6 emu/g to 29.6 emu/g and remanent magnetization from 16.0 emu/g to 15.2 emu/g upon doping, along with a slight decline in the coercivity ratio, indicating altered magnetic interactions due to Sm³⁺ incorporation. These modifications highlight the potential of samarium-doped Ni-Co ferrite nanoparticles for use in magnetic storage, microwave devices, sensors, and biomedical applications such as drug delivery and magnetic hyperthermia.