Cr-substitution effect on the structural and magnetic properties of nano-sized NiFe2O4 prepared via novel chitosan route

Nano-crystalline Cr-substituted nickel ferrites; NiFe2−xCrxO4 (x=0.0-1.0) were prepared using chitosan template method. Differential thermal analysis-thermogravimetric measurements revealed the complete combustion of the gel precursor at 220 °C. X-ray diffraction (XRD) of the as-prepared precursors exhibited the presence of secondary phases besides the entire ferrites. XRD of the calcined precursors at 500 °C indicated single-phase cubic spinel structure for all the prepared samples. The lattice parameter are slightly changed with increasing Cr-content while the particle size and X-ray density gradually decreases. Vibrating sample magnetometer measurements confirmed that Cr-substitution caused a decrease in the saturation magnetization while increasing coercivity. The higher magnetizations obtained compared with other methods in literature enhances using of chitosan as a template for the preparation of other systems. The relatively high coercivity values suggested higher demagnetization magnetic field of the investigated samples. The expected chitosan complexation mechanism as well as the auto-combustion reaction were discussed. A proper cation distribution of the investigated system was suggested through structural data and was confirmed by magnetization studies.