Optimized Heat Generation and Magnetic Properties in Zinc-Substituted Cobalt Ferrite Nanofluids for Biomedical Hyperthermia

The structural, magnetic, and magnetic hyperthermia properties of zinc-doped cobalt ferrite nanoparticles, Zn _x Co _1−x Fe ₂ O ₄ (x = 0.0–0.7), prepared by a hydrothermal method are presented in the current study. XRD confirmed the pure spinel phase for all the compositions. Rietveld refinement has shown systematic changes in cation distribution and lattice distortions reflected in changes in the oxygen positional parameter. Magnetic measurements showed the transition from ferrimagnetic (x = 0.0 and x = 0.2) to superparamagnetic behavior (x ≥ 0.5) and a strong coercivity decrease with a peak in saturation magnetization at x = 0.2. Variations of the magnetic properties are linked to the cation distribution between tetrahedral and octahedral positions, weakening superexchange interactions. As evidenced by the constant decrease in coercivity and anisotropy, magnetic properties softening occurred when the Zn content increased. Magnetic hyperthermia experiments depend a lot on Zn substitution. Thus, SLP and ILP values increased with the Zn content, reaching a maximum at x = 0.6 under various magnetic field amplitudes (65–125 Oe) and frequencies (250–350 kHz). The sample Zn _0.6 Co _0.4 Fe ₂ O ₄ exhibited the best heating efficiency due to the predominance of the relaxation losses in the heat generation processes. This was further confirmed by the quadratic dependence of SLP on magnetic field amplitude, indicating adherence to linear response theory; the field and frequency conditions were also well within clinical safety limits. Therefore, these results suggest using Zn _0.6 Co _0.4 Fe ₂ O ₄ nanoparticles as an efficient agent in magnetic hyperthermia applications.