Mg-Mn-Al ferrites for high frequency applications

The effect of substitution of nonmagnetic Al3+ ions on the electrical and m agnetic properties of Mg-Mn ferrites was studied in the ferrite series Mg0. 9Mn0.1AlxFe2-xO4 where a: varied from 0-0.5 in steps of 0.1. The incorporat ion of Al3+ ions in place of Fe3+ ions results in a decrease of the lattice parameter owing to the smaller size of the substituted ions. The increase in de resistivity has been observed at the expense of the deterioration of magnetic properties, A significant reduction in the values of the initial p ermeability, saturation magnetization and Curie temperature has been observ ed with successive increase of Al3+ ions. These changes in properties have been explained on the basis of various models and other relevant factors, l ike modified cation distribution and magnetic interactions. The high de res istivity, thereby lowering the dielectric losses, and the low value of the saturation magnetization are the desired characteristics of aluminium-subst ituted Mg-Mn ferrites used to prepare microwave devices operating in L, S a nd C bands.