Effect of particle size on the magnetic properties of NixCo1−xFe2O4 (x ≈ 0.3) nanoparticles

► Ni0.3Co0.7Fe2O4 nanoparticles of 12-35 nm sizes were prepared by co-precipitation route. ► Particle-size was found to increase linearly with annealing temperature of the samples. ► Coercivity of the samples observes a maximum value at ∼18 nm. ► MS and Tb were found to increase with increasing size of the nanoparticles.