Structural, electrical and magnetic properties of Co0.5Zn0.5AlxFe2−xO4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) prepared via sol–gel route

Nanoparticles of Co0.5Zn0.5AlxFe2−xO4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by sol–gel method and the influence of Al3+ doping on the properties of Co0.5Zn0.5Fe2O4 was studied. X-ray diffraction studies revealed the formation of single phase spinel type cubical structure having space group Fd-3m. A decreasing trend of the lattice parameter was observed with increasing Al3+ concentration due to the smaller ionic radii of Al3+ ion as compared to Fe3+ ion. TEM was used to characterize the microstructure of the samples and particle size determination, which exhibited the formation of spherical nanoparticles. The particle size was found to be increases up to ∼45 nm after annealing the sample at 1000 °C. Electrical resistivity was found to increase with Al3+ doping, attributed to the decrease in the number of Fe2+–Fe3+ hopping. The activation energy decreased with increasing Al3+ ion concentration, indicating the blocking of conduction mechanism between Fe3+–Fe2+ ions. The value of saturation magnetization decreased, when Fe3+ ions were doped with Al3+ ions in Co0.5Zn0.5Fe2O4; however, the coercivity values increased with increasing Al3+ ion content.