Rare earth garnets (REE3Fe5O12) have magnetic-electric and optical properties that can be used in transmitters, microwave and data storage devices. These properties depend mainly on partial or total substitution of the cationic sites, as well as by the synthesis method used. Therefore, in this work was studied the influence of the substituting cation on the structural and morphological properties of new garnets with formula Sm3−xREExFe5O12 with x = 0.0 - 1.0; obtained by the solid-state reaction method. Characterization of samples was carried out by XRD, Rieltveld refinement, SEM and Raman spectroscopy. The results showed that the substitution favors system stability and formation of garnets single phase with cubic structure and space group of Ia3d (230) at temperatures lower than reported by other authors. The substitution generated a decrease of the lattice parameters, the crystal size and favored particle formation of the order of micrometers (from 1.3 to 3.6 µm).