Effect of cobalt doping on structural parameters, cation distribution and magnetic properties of nickel ferrite nanocrystals

Abstract

Here, thermal heat treatment method has been used for the synthesis of PVP capped nickel ferrite (NiFe2O4) and cobalt doped nickel (Ni0.5Co0.5Fe2O4) spinel ferrite nanocrystals with the aim of investigating the effect of Co doping on the structural and magnetic properties of NiFe2O4 nanocrystals. XRD analysis confirms the formation of a pure form of FCC nanocrystals of spinel ferrite type, where the average crystallite size has been found to be approximately 17 nm and 19 nm respectively for nickel ferrite (NF) and cobalt doped nickel ferrite (CNF) from XRD. Again, HRTEM study gives the average size for NF and CNF as 20 nm and 25 nm respectively. Further, SAED pattern indicates the polycrystallinity of both the sample, whereas EDX analysis confirms the presence of expected elements in the sample. From XRD data analysis different structural parameters such as lattice spacing, lattice constant, tetrahedral and octahedral ionic radii, oxygen position parameter, average cation radius per molecule, ionic packing coefficients (Pa, Pb), the degree of ionic packing (α), vacancy parameter (β), hopping lengths, and bond lengths etc. have been calculated for both nickel and cobalt doped nickel ferrite nanocrystals. Further, obtained cation distribution for NF and CNF nanocrystals from their XRD pattern analysis shows huge change in the distribution as a result of doping. In addition, FTIR spectral analysis also confirms the phase purity of both the samples. Magnetic characterization shows the improvement of different magnetic parameters due to cobalt doping on nickel, thereby making CNF nanocrystals suitable for different application purposes.