Dependence of magnetic properties on crystallite size of CoFe2O4 nanoparticles synthesised by auto-combustion method

Cobalt ferrite (CoFe2O4) nanoparticles were prepared through an auto-combustion method. The results of XRD show that the crystallite size of CoFe2O4 nanoparticles increases from 57 to 105 nm with a slight change in lattice constant as the annealing temperature increases from 300 to 1200C. The magnetic measurements by vibrating sample magnetometer (VSM) show that Ms increases monotonously by increasing the annealing temperature from 300 to 1200C and ChB and Ms reached a maximum when annealing temperature is about 400C due to the change of the grain size.