Role of Cu2+ substitution on the structural and magnetic properties of Ni-ferrite nanoparticles synthesized by the microwave-combustion method

Abstract

Ni1−xCuxFe2O4 (x=0.00, 0.05, 0.10, 0.15, 0.20 and 0.25) nanoparticles were successfully synthesized by microwave-induced combustion process using urea as fuel. The structural and magnetic properties of the samples were determined by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, N2 adsorption–desorption technique, vibrating sample magnetometery (VSM) and Mössbauer spectroscopy. The XRD study confirmed the formation of a single-phase of cubic spinel at low copper contents, whereas CuO is identified as a minor phase for x≥0.20. The crystallite size was found to be in the range 20–30nm. The FTIR spectra show two prominent bands, the broad band located at 582cm−1 corresponds to tetrahedral site and that at 400cm−1 was assigned to the octahedral site. Force constant was calculated for tetrahedral site and was found to be independent on x. The surface area analysis show microporous samples for x=0.00 and 0.05, whereas for x>0.05 the samples exhibited mesoporosity. The specific surface area was found to change with x.Mössbauer spectra measured at RT show a combination of ordered and superparamagnetic behaviors, whereas those collected at 20K elucidate the nature of the obtained phases and the role of Cu2+ substitution on cation distribution in the present system. Room temperature (RT) magnetization results showed that the saturation magnetization increases from 33emu/g for x=0.00 to 48emu/g for x=0.25, and this was attributed to the redistribution of Cu2+cations in the tetrahedral and octahedral sites.