In this research, Y_3-xBi_xFe₅O₁₂ x = (0, 0.1, 0.2, 0.3) were synthesized by a sol–gel method. X-ray diffraction (XRD) patterns confirmed the pure spinel structure for all samples. The magnetic properties of the samples were investigated by the vibration sample magnetometer (VSM). The results obtained from VSM showed that saturation magnetization increases up to
x = 0.1 and then decreases for x>0.1. These variations were attributed to increase of superexchange interaction and spin canting. Furthermore, a model which is based on random distribution of Bi ions in yttrium iron garnet structure was used to achieve the best fit for the Mössbauer patterns. This model explained the effect of Bi substitution on the variation of magnetic hyperfine parameters and also verified the VSM results.