- Abstract The FMR spectra of electron-doped Sm 0.2 Ca 0.8 Mn 1− x Ru x O 3 (0≤ x ≤0.08) system are measured and analyzed in the temperature interval 100≤T≤320 K , including all critical points of magnetic transitions. It is shown that the origin of macroscopic magnetization in the parent Sm 0.2 Ca 0.8 MnO 3 and Ru-doped compounds is essentially different. The bound magnetic polarons formation at temperatures below the Neel point is suggested to be responsible for the appearance of a minute ‘spontaneous’ magnetic moment in Sm 0.2 Ca 0.8 MnO 3 . Doping with Ru induces formation of ‘conventional’ ferromagnetic phase in antiferromagnetic matrix. Such a phase is characterized by a Curie temperature, which is higher than the Neel temperature of the matrix. Magnetic phase diagrams of Sm 0.2 Ca 0.8 Mn 1− x Ru x O 3 determined by ferromagnetic resonance and dc magnetic measurements are discussed.