Structural, optical, and magnetic properties of Co-doped ZnO nanorods: Advancements in room temperature ferromagnetic behavior for spintronic applications

In the search for a diluted magnetic semiconductor (DMS) for spintronics devices, Zn1-xCoxO (x = 0, 0.020, 0.035, 0.050, and 0.065) nanoparticles (NPs) were synthesized using a simple and cost-effective co -precipitation technique. To demonstrate the advantages of Co -doping, the morphological, microstructure, optical, and magnetic properties of the Co -doped ZnO NPs were extensively investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), selected area electron diffraction (SAED), Raman spectroscopy, ultraviolet-visible (UV-vis.) spectroscopy, and vibrating sample magnetometer (VSM) techniques. The synthesized NPs exhibited a hexagonal wurtzite structure. Their lattice parameters were found to decrease with increasing Co -doped wt.%, confirming the incorporation of Co2+ in ZnO. The solid solution limit of Co-ZnO NPs was found to be Zn0.965Co0.035O. The crystallite sizes of the NPs were found to vary from 38.36 to 39.68 nm. Pure ZnO formed both the nanospheres (NSs) and nanorods (NRs), but Co -doped ZnO generated NRs only. The narrowest NR, with a diameter of 94 nm, was obtained for the Zn0.965Co0.035O. With a 'Blue shift', the band gap energies were found to increase from 3.34 to 3.61 eV. The ZnO showed diamagnetic behavior whereas all the Co -doped NRs showed room temperature ferromagnetic (RTFM) properties. The highest magnetization values (Ms) 5.07 x 10-2 emu/g and (mu B/Co2+) 14.93 x 10-3 were observed for Zn0.965Co0.035O NRs, and these values are several times higher than many previously reported values. The origin of the ferromagnetism was found to be an intrinsic property of the Co -doped ZnO NRs. The study successfully synthesized Co -doped ZnO DMS, which could be used for spintronic-based photoelectronic and ferromagnetic devices.