Impact of erbium (Er) doping on the structural and magnetic properties of Ni-Cu (Ni0.1Cu0.9Fe2O4) nanoferrites

Abstract

Rare earth erbium (Er) doped spinel Ni-Cu nanoferrites having chemical composition Ni0.1Cu0.9ErxFe2-xO4 (x = 0.00, 0.010, 0.015, 0.020, 0.025 and 0.030) were prepared by standard citrate-gel auto combustion (CGAC) technique. X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy, and vibrating sample magnetometer (VSM) were used to characterize the structural, optical, and magnetic properties of these ferrites. X-ray diffraction spectra clearly revealed that the pure Ni-Cu ferrite shows a tetrahedral distortion due to John Tellar ion (Cu2+) subsequently erbium doping transformed the tetragonal phase in to the cubic spinel phase with minor traces of impurity phase. Using Scherer's equation, the average crystallite size was found to be between 7.39 and 27.78 nm. The average crystallite size (7.39–27.78 nm) obtained from XRD and average grain size (64.84–83.36 nm) measured from FESEM confirmed the nano structure of prepared samples. Energy dispersive analysis X-ray (EDAX) spectra with elemental analysis verified the existence of Ni, Cu, Er, Fe, and O elements without any impurities. Two prominent absorption bands detected in FTIR spectra within the wave number range of 575.54–586.73 cm−1 (υ1) and 370.24–372.53 cm−1 (υ2) indicate the stretching vibrations of Fe3+-O2− complexes in tetrahedral and octahedral sites of spinel structure respectively. TG and DTA techniques were used to analyze the thermal behavior of the composition x = 0.030. It was observed that exhibiting a rapid loss in weight after 900 °C promotes the formation of pure phase nanoferrite. Direct and indirect optical band gap values were computed from UV absorption studies with Tauc plots. The obtained band gap values revealed the semiconducting behavior of the prepared samples. VSM was used to explore the magnetization of samples as a function of field at temperatures of 15 K and 300 K. The maximum saturation magnetization (Ms) was observed for x = 0.030 composition and it was estimated as 31.18 emu/g at 15 K and 26.80 emu/g at 300 K temperatures. The experimental and theoretical values of lattice parameter and room temperature magnetic moment are good agreement with suggested cation distribution.