Controlling the properties of magnesium–manganese ferrites

The effect of substitution of In3+, Al3+ and Cr3+ ions on the electrical and magnetic properties of Mg–Mn ferrites has been investigated. The substitution of In3+ ions in place of Fe3+ ions, resulted in an increase of lattice parameter, owing to the larger size of the substituted ions, whereas lattice parameter decreased on substituting Al3+ and Cr3+ ions in place of the Fe3+ ions, owing to the smaller sizes of these substituted ions. D.C. resistivity was found to increase with the substitution of In3+, Al3+ or Cr3+ ions in the Mg–Mn ferrite system. The improvement in the d.c. resistivity has been observed at the expense of deterioration in the magnetic properties of Al3+ and Cr3+ substituted Mg–Mn ferrites. A significant reduction in the value of initial permeability, saturation magnetization and Curie temperature were observed with successive increase of Al3+ and Cr3+ ions. The saturation magnetization and initial permeability were found to increase with incorporation of In3+ ions. A marked increase in the value of initial permeability was found for the Mg 0.9Mn0.1In0.5Fe1.5O4 ferrites. The Curie temperature was found to decrease with an increase of In3+ ion concentration. These changes in the properties are explained on the basis of a modified cation distribution and their magnetic interactions and various models.