A comprehensive study of Co1-xNixFe2O4 nanoparticles fabricated via three different synthetic methods

We report on three different synthetic methods for producing Co1-xNixFe2O4 nanoparticles (x = 0.0, 0.4, and 1.0): combustion (C), hydrothermal (HT), and forced hydrolysis (FH). Theoretical fittings of the ferromagnetic resonance (FMR) lines were achieved by considering a proposed four-fold symmetry model for randomly dispersed magnetic nanoparticles (NPs). The average grain size (D), between 10 and 80 nm, and magnetic properties are found to depend strongly on both the selectedsynthesis route and stoichiometry (x). Interestingly, while the HT- and FH-methods provide NPs with no systematic dependence of coercive field and remanence, upon x or D, the C-method showedmonotonic dependence. The magnetocrystalline anisotropy field (H-a), extracted from simulating the FMR spectra, systematically reduces with increasing x, regardless the synthetic route used. Worth mentioning that the largest (smallest) variation in H-a is observed for the C-method (HT-method) equals to Delta H-a = -3853 Oe (Delta H-a = -1676 Oe).