Structure and magnetic properties of (Co, Ce) co-doped ZnO-based diluted magnetic semiconductor nanoparticles

We successfully fabricated ZnO, Zn0.96Co0.04O, Zn0.95Co0.04Ce0.01O, Zn0.94Co0.04Ce0.02O, and Zn0.92Co0.04Ce0.04O nanoparticles and studied their room-temperature structure and magnetic properties. The X-rays diffraction (XRD) patterns of all the samples confirmed the presence of a wurtzite-type structure. XRD and Transmission Electron Microscopy (TEM) results showed that Zn2+ ions originally at tetrahedral sites were replaced by high-spin Co2+ and Ce3+ ions. This study also showed that with an increase in co-dopant concentration, the average grain size of the samples increased. We found that Zn0.96-xCo0.04CexO (x = 0.0, 0.1, 0.2, and 0.4) nanoparticles were ferromagnetic with a Curie temperature above 300 K. In addition, a large increase in ferromagnetism, i.e., high coercivity field, Hc, of 90Oe and remanent magnetization, Mr, of 0.25 × 10−2 emu/g, was observed for Zn0.96-xCo0.04CexO (x = 0.2) nanoparticles. The origins of ferromagnetism may be either due to the intrinsic nature of Co and Ce co-doped samples or to the presence of certain undetected spinel-type impurities in the samples. Also, it was concluded that Co and Ce incorporation are responsible for ferromagnetism in the doped sample. The doping generates oxygen vacancies, which trap charges and cause a rise in F-centers, resulting in exchange interactions with impurity atoms and increased magnetism. All these results showed that co-doped ZnO-based diluted magnetic semiconductors could be considered for spin-based electronics and optoelectronics devices.