Structural and magnetic characteristics of Co1−xNix/2Srx/2Fe2O4 nanoparticles

► Co1−xNix/2Srx/2Fe2O4 (x=0-0.5) nanoparticles were prepared by a reverse micelle method. ► Ni and Sr enter preferably at site B and substitution of cobalt does not change the magnetic hyperfine field at the site A much. ► Good agreement with the experimental data of susceptibility. ► Vogel-Fulcher model confirms the existence of strong interactions between nanoparticles.