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

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 (FUR) spectroscopy, N-2 adsorption-desorption technique, vibrating sample magnetometery (VSM) and Mossbauer 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 20-30 nm. The FTIR spectra show two prominent bands, the broad band located at 582 cm(-1) corresponds to tetrahedral site and that at 400 cm(-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. Mossbauer spectra measured at RT show a combination of ordered and superparamagnetic behaviors, whereas those collected at 20 K 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 33 emu/g for x=0.00 to 48 emu/g for x=0.25, and this was attributed to the redistribution of Cu2+ cations in the tetrahedral and octahedral sites. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.