Influence of pH on structural and magnetic properties of nanocrystalline cobalt ferrites synthesized by sol–gel method

Abstract

In the present study, nanocrystalline cobalt ferrite with various sizes was synthesized by sol–gel auto combustion method at different pH condition. The XRD analysis confirmed the formation of single phase cubic cobalt ferrite when the pH reaches at 7. The average crystallite size of the samples increased from 14 to 19 nm indicating the influence of pH of the precipitating medium. The FT-IR spectra of the samples show strong absorption peak in the wave number range 400 to 600 cm−1 which are assigned to tetrahedral and octahedral metal complexes, confirmed the presence of metal - oxygen ion complexes within the spinel lattice. HR-TEM micrograph reveals the formation of nano flakes and the particle size obtained well matches with that estimated from XRD. Vibrating sample magnetometer (VSM) was used to investigate the magnetic properties of the sample. The magnetization of nanoparticles shows a strong dependence on pH of the medium. Magnetization curve fitting, a theoretical approach, is used to determine the various magnetic phase contributions to the total magnetization value and it reveals the paramagnetic phase along with ferromagnetic phase in the samples. The % contribution of ferromagnetic component increases with increasing the pH of the precipitating medium. The room temperature Mossbauer spectrum of a selected sample also confirmed the ferromagnetic nature of the sample.In the present study, nanocrystalline cobalt ferrite with various sizes was synthesized by sol–gel auto combustion method at different pH condition. The XRD analysis confirmed the formation of single phase cubic cobalt ferrite when the pH reaches at 7. The average crystallite size of the samples increased from 14 to 19 nm indicating the influence of pH of the precipitating medium. The FT-IR spectra of the samples show strong absorption peak in the wave number range 400 to 600 cm−1 which are assigned to tetrahedral and octahedral metal complexes, confirmed the presence of metal - oxygen ion complexes within the spinel lattice. HR-TEM micrograph reveals the formation of nano flakes and the particle size obtained well matches with that estimated from XRD. Vibrating sample magnetometer (VSM) was used to investigate the magnetic properties of the sample. The magnetization of nanoparticles shows a strong dependence on pH of the medium. Magnetization curve fitting, a theoretical approach, is used to determine th...