Hossein Nikmanesh

(x = 0, 0.2, 0.4, 0.6, 0.8 at %) nanoparticles. X-Ray Diffraction (XRD) analysis indicates that nanoparticles have a single-phase spinel structure. The lattice constant (a) was calculated by the Rietveld method through MAUD program. The crystallite size (D), mean ionic radii of A and B sites, bond lengths, interionic bond angels and distances of samples were also calculated. Variation of structural parameters agrees with the cation distribution determined in the magnetic study section. The FESEM images confirmed the data extracted from XRD analysis. The change of particles' shape from spherical to octahedral by Cr doping was also observed. The particles’ size of all the samples was studied by drawing the size distribution plots. It was indicated that the size of ferrite particles was varying in the range of 21–110 nm. Increment of Cr3+ content caused the saturation magnetization to be declined, while the coercive field illustrated an opposite behaviour. The effect of size and shape of particles as well as the cation distribution were key factors employed to justify the magnetic properties of Co–Cr ferrite structures. The novel outcome of this work is that the coercive field of the ferrite samples can be tailored as a parameter for high coercivity-needed applications by the effect of shape and size of particles.