Synthesis and magnetic properties of octahedral ferrite NixCo1-xFe2O4 nanocrystals

A series of Ni doped cobalt ferrite compounds with the formula Ni (chi) Co1-chi Fe2O4 where x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 were prepared using a hydrothermal method and subsequently sintered/annealed at 600 degrees C for 3 h. The influence of the Ni content on the lattice parameter, a, stretching vibration and the magnetization of specimens were subsequently studied. XRD and FTIR were used to investigate structure and composition variations. All samples were found to have a cubic spinel structure. SEM was used to study morphological variations. The results indicate that the average particle sizes are between 30-35 nm with a narrow size distribution along with nanocrystals forming of regular octahedrons. A decrease in the peak to peak line width and increase in resonance field with increasing Ni content were observed from ESR measurements. Based on ESR results, a core-shell type of formation was proposed where the core is made up of undoped CoFe2O4 and the shell is Ni2+ doped CoFe2O4. (c) Versita Warsaw and Springer-Verlag Berlin Heidelberg. All rights reserved.