Effect of Gd and La doping on the structure, optical and magnetic properties of NiZnCo ferrites

The rare earth doped NiZnCo ferrites were prepared by the sol-gel auto-combustion method. X-ray diffraction, scanning electron microscopy, infrared spectroscopy, ultraviolet visible spectrophotometer and vibrating sample magnetometer were used to characterize the microstructure, optical and magnetic properties of rare earth doped NiZnCo ferrite. The results show that with the increase of rare earth doping amount, the lattice parameters of NiZnCo ferrite increase firstly and then decrease, the grain size decreases monotonously. And the second phase appears when the La and Gd doping amount is 0.06 and 0.1, respectively. The morphology of rare earth doped ferrites is relatively homogeneous sphere. The cations are redistributed in the crystal lattice. When the amount of dopant is small, the rare earth ions occupy both A-site and B-site. Increasing dopants, the rare earth ions occupy the B-sites. The critical content is 0.02 for La dopant, while it is 0.06 for Gd. La doping results in broadening of the band gap; Doping Gd results in narrowing of the band gap. The saturation magnetization decreased linearly from 108 emu/g to 43 emu/g and 85 emu/g, respectively, with the increase of Gd and La doping. The faster downtrend for Gd doped ferrites is due to its greater solubility.