Optical and room-temperature ferromagnetic properties of Ni-doped CuO nanocrystals prepared via auto-combustion method

The pure and Ni-doped CuO nanocrystals were prepared via auto-combustion method and characterized by X-ray diffraction, scanning electron microscope, UV spectroscopy, and vibrating sample magnetometer method. The X-ray diffraction patterns of all samples revealed the monoclinic CuO nanocrystals with the nanocrystalline phase. XRD data revealed that the lattice constants of CuO nanocrystals were decreased with increasing Ni concentration which indicate that Ni2+ ions incorporated in CuO lattice. The average crystallite size of nanocrystals is intended by Scherer's formula and found in the range of 21-24 nm. The variation of microstrain was investigated for pure and Ni-doped CuO samples. The SEM images exhibited that the prepared particles have spherical-like structure. The optical absorption spectra of the nanoparticles obtained using UV-Vis spectrophotometer show the blue-shift with increasing Ni doping. The optical band-gap energy increased with increasing Ni doping concentration due to the sp-d exchange interaction between d localized electrons of Ni. Magnetic measurement showed a ferromagnetic behavior at room temperature. Structural and magnetic properties are also discussed in detail.