Compositional Optimizations and Magnetic Performances of CoxFe3−xO4$${\mathrm{Co}}_x{\mathrm{Fe}}_{3-x}{\mathrm O}_4$$ Nanoclusters

This study reports the synthesis and comprehensive magnetic characterization of nanoparticles across a compositional spectrum ( x = 0.6, 0.8, 1.0, 1.2, and 1.4) using a precisely controlled combustion reaction approach. Morphological analysis revealed well‐defined single‐domain nanoparticles with an average diameter of nm. Magnetic characterization demonstrated that coercivity increases systematically with cobalt substitution, reaching a maximum for , while nonmonotonic behavior was observed around x = 0.8. Saturation magnetization reached its peak at . Furthermore, the magnetocrystalline anisotropy constant showed a significant increase with higher cobalt content. The ferrimagnetic to superparamagnetic transition was confirmed through both zero‐field cooling–field‐cooling measurements and theoretical estimations of blocking temperature, showing strong agreement across compositions. A high magnetic field ( 150 kOe) was required to approach saturation due to large anisotropy fields in Co‐rich compositions. The nanoclusters exhibit tunable magnetic properties through compositional adjustments, offering design principles for applications in permanent magnets, high‐density magnetic storage, and biomedical fields.