Structural, Optical and Room Temperature Ferromagnetic Properties of Co-Doped Zinc Oxide Nanorods Prepared by Sol–Gel Method

Abstract

This study reported the synthesis of cobalt (Co)-doped ZnO nanorods using sol–gel method and characterized their microstructures, morphologies, optical and ferromagnetic properties at room temperature by X-ray diffraction, scanning electron microscopy, ultraviolet-visible absorption spectroscopy, photoluminescence spectrometry and vibrating sample magnetometry. The results revealed that the formation of the hexagonal shaped wurtzite of Co-doped ZnO nanorods for Co content ≤0.01% suggested that Co2+ occupied the sites of Zn2+ ions in the ZnO crystal lattice without forming any secondary phase. Moreover, the optical energy band gap (Eg) of the Co-doped ZnO nanorods decreased with increasing Co concentration, while the absorption band edges were at 565, 610 and 653 nm, corresponding to d–d transition of Co2+ ions in the tetrahedral field of ZnO. Furthermore, the strong Zn interstitials and oxygen vacancy defects induced ferromagnetism in the Co-doped ZnO nanorods with a Tc ≥ 300 K. The optimal values of saturation magnetization (Ms), the remanent magnetization (Mr) and coercive field (Hc) were 1.23 × 10–2 emu/g, 1.7 × 10–3 emu/g and 76 Oe, respectively. These findings suggested that the Co-doped ZnO nanorods exhibited promising attributes for the development of semiconductor devices with excellent ferromagnetic properties at room temperature.