Effect of Cobalt Doping on Structural, Optical, and Magnetic Properties of ZnO Nanoparticles Synthesized by Coprecipitation Method

Zn 1– x Co x O ( x = 0, 0.05, 0.10, and 0.15) nanoparticles (NPs) were synthesized by a coprecipitation method. The crystalline sizes of synthesized samples were calculated from the powder XRD patterns, which were found to decrease with the increase of cobalt content. The FT-IR spectra confirmed the Zn–O stretching bands at 468, 456, 452, and 461 cm –1 for the respective ZnO NPs. SEM images demonstrated the distinct flowerlike morphology. The photoluminescence spectra of all the samples exhibited a broad emission in the visible range. XPS studies were carried out for Zn 0.90 Co 0.10 O NPs. The carriers (donors) bound on the Co sites were observed from the micro-Raman spectroscopic studies. The pure and Co-doped ZnO NPs showed significant changes in the M – H loop where the diamagnetic behavior of ZnO changes to ferromagnetic nature when doping with Co. Oxygen vacancies and zinc interstitials were found to be the main reasons for room-temperature ferromagnetism in the Co-doped ZnO NPs with the support of the results obtained from the EPR, photoluminescence, and micro-Raman studies.