To study defect origin of ferromagnetism, hollow spheres are better candidates as they are less agglomerated and has both sides of the wall free, as compared to nanoparticles and thin films respectively. Our results show improved magnetic properties of GaN, ZnAl2O4 and MgO hollow spheres over their earlier reported nanoparticle counterparts. Photoluminescence spectroscopy supports our magnetic findings. (C) 2011 Elsevier B.V. All rights reserved.