Effect of Bi3+ Ion Substitution on Magnetic Properties of Cobalt Nano Ferrites Prepared by Sol-Gel Combustion Method

Abstract

Bismuth substituted cobalt nano ferrites with the chemical composition Co Bi x Fe 2-x O 4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method. The phase identification of prepared samples is characterised by X-ray powder diffraction (XRD) method, which confirms the formation of a single phase fcc spinal structure. The mean crystallite sizes of all prepared samples were obtained within the range of 21 (±5) nm. Transmission Electron Microscopy (TEM) images also confirmed the crystallite size of all the synthesised samples was in nano range. With the effect of Bi 3+ ion substitution on spinal cobalt ferrite, the magnetic properties were investigated by using Vibration Sample Magnetometer (VSM). The obtained hysteresis (M-H) curves of all the samples were analysed under the applied magnetic field of range ± 10 K Oe at 300 K. The magnetic properties such as saturation magnetisation (M s ), remnant magnetization (M r ) and coercivity (H c ) values are tabulated, which show a decrease in trend as the bismuth ion concentration increases. This is due to the addition of Bi 3+ ion in the place of Fe 3+ ion (octahedral site) and hence the Bi 3+ -Fe 3+ ion interaction predominates as compared with the Fe 2+ -Fe 3+ ion interaction. The data obtained from magnetic studies, the variation among the magnetic properties have been investigated for all the prepared samples.