X-Ray and Infrared Studies on Superparamagnetic Ni-Zn Ferrite Nanocrystals

Series of zinc-substituted nickel ferrite, Ni1-x Zn (x) Fe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0), nanoparticles were synthesized at low temperature by using sol-gel auto-combustion method. Powder X-ray diffraction confirmed the single-spinel structure of the synthesized Ni-Zn ferrite nanocrystals with average crystallite size was found to be 30 nm which is close to that of critical size for exhibiting superparamagnetism which was further verified from Mossbauer spectroscopic studies. The stoichiometric analysis of the ferrite samples carried out by employing energy-dispersive X-ray spectroscopy is found to be as expected. Results of infrared spectroscopic studies carried out on these superparamagnetic ferrite nanocrystals are reported in this paper. The tetrahedral and octahedral absorption band frequencies suggested the spinel structure of the ferrite samples and its behavior with zinc content x is attributed to the nanosize effect and occupation of zinc cations at the octahedral [B] sites. Further, the force constants are found to be in the reported range of that for ferrites.