Investigations of the structure and tunable magnetic properties of Cu doped cobalt chromite nanoparticles

This article reports the synthesis, microstructural, magnetic and optical properties of copper ions substituted cobalt chromite nanoparticles. We have prepared four nanosized chromite samples with a general composition of CuxCo1-xCr2O4 (x = 0.0, 0.1, 0.2 and 0.3) using conventional wet chemical co-precipitation method. The x-ray diffraction profiles verified the presence of pure spinel crystal structure of the samples. Using the Williamson Hall (W-H) method, the average crystallite size of all the samples were calculated to be between 11 nm and 16 nm. A tensile microstrain in all the samples was noticed. Surface morphology and average particle size of doped cobalt chromite nanocrystals was examined using HRTEM images. A moderate increment in the optical band gap was detected with increasing Cu ions in cobalt chromite nanoparticles which is attributed to the nanosize effect of the samples. The presence of all five distinctive Raman active modes in the chromite samples ensured phase purity and a decrease in crystal symmetry was also observed as the amount of Cu dopants was increased. Due to low magnetic moment of Cu2+ ions when compared with Co2+ ions, incorporation of copper ions reduces the coercive field of the host chromite system. With increasing Cu percentage in chromite especially for 30 % Cu doped sample, the spin-spiral transition TS vanishes which indicates TS is affected by the dopant concentrations.