Correlation of cation distribution with structure, magnetic and electrical properties of ultrafine Ni2+-doped CoFe2O4

This work presents the estimation of cation distribution of ultrafine NixCo1−xFe2O4 nano-ferrites (x = 0, 0.25, 0.5, 0.75 and 1) from structure, magnetic and electrical investigations. “Sol gel” was the method used to synthesize Ni–Co ferrites. Ni2+-doped CoFe2O4 nanostructure has a broad range of electromagnetic applications due to its controllable magnetic and electrical properties. From XRD patterns, the formation of pure phase was obvious, and the crystallite size ranged from 9 to 12 nm. These sizes are small enough to achieve suitable signal-to-noise ratio for high-density recording media and have more opportunities for technological application, especially in medical fields. Besides, the variation of theoretical lattice parameter with x-content was in a good agreement with experimental ones. Field Emission Scanning Electron Microscope (FESEM) revealed the formation of small nanosphere particles with gradual size reduction on addition of Ni2+ ions. Energy-Dispersive X-ray analysis (EDX) confirmed the purity of prepared samples. Magnetic parameters (Ms, Mr and Hc) were determined from Vibrating Sample Magnetometer (VSM). It was found that both Ms and Hc have gradual decrease with increasing x-content. Curie temperature was determined from the variation of relative permeability with temperature and showed also a gradual decrease with addition of Ni2+ ions. Temperature dependence of both DC electrical resistivity and thermoelectric power coefficient were carried out in the temperature range 385–548 K. The resistivity showed a gradual decrease with increasing x-content. However, the negativity of thermoelectric power coefficient showed a gradual increase with addition of Ni2+ ions. Conduction mechanism was deduced for all studied samples from activation energy values. The cation distribution was proposed such that it could verify the lattice parameter and magnetization of each composition as well as the behavior of resistivity and thermoelectric power.