A set of compounds with the formula MgAg0.4R0.2Fe1.4O4 where R is Lanthanum (La3+), Terbium (Tb3+), and Yttrium (Y3+), were prepared by the flash combustion technique. The effect of rare earths ions on some properties of silver doped was investigated. The obtained data indicated that, by introducing a relatively small amount of rare earths ions instead of Fe2O3 ions, an important modification of both the structure and the magnetic properties can be obtained. The Curie temperature, effective magnetic moment and exchange interaction are affected by these substitutions. The effect of rare earth ions were explained both by their partial diffusion in the spinel lattice and by the formation of the crystalline secondary phase on the grain boundaries.