Room temperature ferromagnetism in combustion synthesized nanocrystalline Co, Al co-doped ZnO

Pure and Co, Al co-doped ZnO(Zn1−x−yCoxAlyO; x = 0.04, 0.03, 0.02; y = 0.01, 0.02, 0.03) nanoparticles were synthesized by wet chemical combustion method at 500 °C for various doping levels using zinc, cobalt and aluminium nitrates as precursors. The synthesized powders were calcined at 600 °C and sintered at 1000 °C after uni-axial compaction. Structure, morphology and the presence of magnetism in combusted and sintered materials of pure and doped ZnO were examined. At room temperature, both the calcined nanoparticles and sintered compacts of pure ZnO exhibited paramagnetism. But, ferromagnetism was observed for Co and Al co-doped ZnO (diluted magnetic semiconductor) nanoparticles calcined at 600 °C. Also, it was found that the ferromagnetism increased correspondingly for the calcined particles with Co concentration. Whereas, a strong paramagnetic behavior was observed for the sintered compacts of various concentrations of Co and Al dopants due to grain growth.