Effect of oxygen vacancy on magnetism of ZnO:Co single-crystalline nanorods

Abstract Co-doped ZnO single-crystalline nanorods were prepared by the modified microemulsion route. The crystalline structure, morphology, oxygen vacancy emission, and hysteresis loop at low temperature and room temperature of as-prepared materials were characterized by XRD, TEM, PL spectra, and magnetic measurement respectively. The nanorods are 60–90 nm in diameter and about 2 μm in length. X-ray diffraction data, TEM images and selected area electron diffraction patterns confirm that the materials synthesized in optimal conditions are ZnO:Co single crystalline solid solution without any impurities related to Co. Magnetic measurements show that different surfactants as template in synthesis process result in ferromagnetism and paramagnetism in Zn0.95Co0.05O nanorods. The PL spectra show that the ferromagnetic samples exhibit strong oxygen vacancy emission whereas in the paramagnetic samples the oxygen vacancy emission is absent, indicating that the defects may stabilize ferromagnetic order in diluted magnetic semiconductors, resulting in high-temperature ferromagnetism.