The effect of non-magnetic Al3+ ions on the structure and electromagnetic properties of MgCuZn ferrite

A series of Al substituted MgCuZn ferrite powders with composition Mg0.3Cu0.2Zn0.52AlxFe1.98−xO3.99 (0.00≤x≤0.06) have been synthesized with nano-sized precursor powders through the nitrate-citrate auto-combustion route. These powders were calcined, compacted and sintered at 900 °C for 4 h. X-ray diffraction patterns show the formation of cubic spinel structure. Infrared spectra indicate two fundamental absorption bands corresponding to the tetrahedral and octahedral complexes, respectively. A significant increase in density and grain size is observed with increasing Al content. The room temperature saturation magnetization increases for x=0.015 and then decreases for further increase in Al substitution. The initial permeability increases with the Al content attributed to the increase in the grain size and density. Curie temperature is found to be dependent on the Al concentration and it decreases due to decrease in the number of super-exchange interactions between Fe3+ ions in the tetrahedral and octahedral sites.