Effect of Gamma Irradiation on Structural and Magnetic Properties of Bi Substituted Cobalt Ferrite Nanoparticles

Abstract

Magnetic materials with spinel structure have been interesting due to their wide range of applications for large spin polarization and high magnetic critical temperatures; well above the room temperature. Ferrimagnetic and electrical properties of the spinel ferrites are strongly influenced by the distribution of cations along with Fe3+-Fe2+ between the tetrahedral and octahedral sites. Cobalt ferrite, an inverse spinel at bulk and partial inversion in nano order has been important for discussion. The interplay of cations for site occupation tunes the electric and magnetic properties of the cobalt ferrite. In the present study attempts have been made to observe magnetic properties of both gamma irradiated (1 KGy) and unirradiated cobalt ferrite by substituting Bi2+ in place of Fe. Bi3+ substituted spinel cobalt ferrite nanoparticles was prepared by auto combustion method. Phase formation and surface morphology was confirmed by the XRD and FESEM respectively. The particle size was estimated to be in nano range from study of FESEM image. Particle size and hoping length were increased with the substitution of Bi3+ due to the large size of bismuth compared to the iron. The magnetic properties of Bi substituted cobalt ferrite nanoparticles analyzed before and after gamma irradiation. Before gamma radiation saturation magnetization and remnant magnetization increased with Bi substitution while coercivity is decreased. In case of irradiated samples there is irregular variation of magnetic properties with bismuth substitution. In this case saturation magnetization and remnant magnetization has increased from parent to 5 % substitution after that it is decreased. Coercivity showed higher value in 10 % substitution and remaining samples showed lower than the parent cobalt ferrite.