Ferromagnetism in Cu2+ doped ZnO nanoparticles and their physical properties

Abstract

Cu2+ doped ZnO nanoparticles designated as Zn1−xCuxO (x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) were prepared by sol–gel auto combustion technique. The modifications in structure, morphology, band gap, electrical, dielectric and magnetic properties due to Cu2+ doping were investigated through XRD, FE-SEM/EDAX, TEM/SAED, Raman, FT-IR, UV–Vis and VSM respectively. The analysis of XRD pattern reveals the incorporation of the dopants Cu2+ into ZnO lattice. The XRD spectra show that all the synthesized nanoparticles are a single crystalline phase with hexagonal wurtzite structure. The analysis of FE-SEM indicates that Cu2+ doping affects the surface morphology of ZnO. The compositional study performed by EDAX confirmed the presence of Zn, O, and Cu in stoichiometric proportion. TEM micrographs show the spherical shape of nanocrystals with small agglomeration. SAED patterns confirm the crystalline nature with hexagonal wurtzite structure. Raman spectra show the strongest peak at 437 cm−1 related to vibration of oxygen atoms in ZnO and also confirms optical phonon modes. FTIR result confirms the successful accompanying of Cu2+ ions into ZnO crystal lattice without changing its original structure. From DC electrical resistivity measurements it was found that electrical resistivity enhanced with increase in Cu2+ content. The measured dielectric parameters decreased with increase in Cu2+ content. An optical study revealed that the energy band gap decreased with doping of Cu2+ ions into ZnO nanoparticles. The VSM analysis shows the transformation of paramagnetic to superparamagnetic and superparamgnetic to ferromagnetic at room temperature due to Cu2+ doping in ZnO nanoparticles. The enhanced physical properties revealed that the prepared Cu2+ doped ZnO nanoparticles are the potential candidate for high-frequency devices, optoelectronic devices and spintronics devices application.