In this work, we synthesized and characterized structurally the rare earth iron garnets R3Fe4.9Al0.1O12 (R = Sm, Gd) by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman microscopy, and magnetization. The samples were synthesized using the co-precipitation synthesis method and calcined at a temperature between 500 and 900 °C stepwise 100 °C. Sm3Fe4.9Al0.1O12 and Gd3Fe4.9Al0.1O12 powder samples were indexed with a garnet cubic structure belonging to the Ia3?d space group. Structural analyzes indicate that the inclusion of Al instead of Fe slightly decreases the temperature of magnetic ordering. Crystallite sizes calculated from Scherrer's equation and Williamson-Hall method from XDR were 118 nm and 103 nm for Sm3Fe4.9Al0.1O12 and Gd3Fe4.9Al0.1O12 respectively. The SEM analysis results revealed that the particles were formed with average sizes of 469 nm to Sm3Fe4.9Al0.1O...