Cation distribution, magnetic and structural properties of CoCrxFe2-xO4: Effect of calcination temperature and chromium substitution

The influence of chromium doping and the calcination temperature on the structural, morphological, cation distribution and magnetic properties of CoCrxFe2-xO4 where x = 0.0, 0.25, 0.5, 0.75 and 1 were investigated in detail. The X-ray diffraction (XRD) analysis using the Rietveld refinement technique proved the nanocrystalline single-phase, chromium doped cobalt ferrite samples. It is observed that the lattice parameter 'a' decreases with increasing the chromium concentrations, while lattice parameter gradually enhances with increasing of calcination temperature. The cation distribution was inferred from the analysis of intensity of XRD as well magnetic properties. Magnetic measurements informed that both of the coercivity (H-c) and saturation magnetization (M-s) overall decrease with increasing chromium substitution. Also, with rising of calcination temperature from 350 to 1000 degrees C, for un-doped cobalt ferrite sample, M-s is increased from 31 to78 emu/gr, respectively. These magnetic behaviors could be explained by the cation distribution and crystallite size enhancement. The H-c enhancement for the heat-treated samples until 700 degrees C can be attributed to the crystal growth within the single domain region, while decreasing H-c by further increasing calcination temperature to 1000 degrees C, is due to the transformation of single domain nanoparticles to multi-domain particles. The reduced hysteresis loops due to decreasing M-s and H-c with increase in chromium concentration, which in turn lowered the coercive field and softened the material, favoring its application in high-frequency transformers.