Nanocrystallite interface effect and exchange bias phenomenology in Cr2O3 and NiO nanoparticles

► The appearance of weak ferromagnetism in nanocrystalline NiO and Cr2O3. ► Considerable exchange bias effect for NiO whereas weak effect for Cr3O3. ► Pinning mechanism at the FM-surface and the AFM-core interface leads to an exchange bias.