Fig. 1. (a) Typical XRD spectra of uncoated (dark lines) and OAMNP (gray lines) samples, (b) close-up of the main peaks, (c) SEM micrograph of the OAMNP, (d) size distribution plot fitted to a normal data regression, (e) SEM of uncoated MNPs, and (f) corresponding plot including the data regression.

Fig. 2. FTIR spectra of uncoated Fe₃O₄ nanoparticles (dark), pure oleic acid (blue), and OAMNP (gray).

Fig. 3. (a) Relative mass Mversus temperature of OAMNP over the interval 30 °C < T < 850 °C and (b) corresponding derivative in the same temperature interval.

Fig. 4. The pH-dependent (a) Zeta potential, (b) their corresponding hydrodynamic diameters, and (c) polydispersity index of water-suspended coated (open circles) and uncoated (black circles) MNPs.

Fig. 5. (a) Magnetization loops at room temperature of uncoated and coated MNPs, and (b) their corresponding ZFC–FC graphs using H = 100 Oe.

Fig. 6. Time dependent (a) temperature increment during 2 min applying H = 25 mT with five values of f, and (b) power density.

Fig. 7. (a) Temperature increment during 2 min applying f = 330 kHz with five steps of H, and (b) the dependence PversusH with the corresponding quadratic data regression.