Magnetization anomalies in the superconducting state of RuSr2GdCu2O8 and the magnetic study of Sr2GdRuO6

d.c. magnetization measurements performed on a polycrystalline sample of RuSr2GdCu2O8 (Ru-1212) showed distinct peaks of the magnetization upon entering the superconducting state. Since Sr2GdRuO6 (Sr-2116) is the precursor for the preparation of Ru-1212, a detailed investigation of the magnetic properties of Sr-2116 was carried out. Although similarities were observed in the magnetic behavior of Sr-2116 and Ru-1212 in the temperature range of the observed peaks, we can exclude, based on a quantitative comparison, that the anomalies observed for Ru-1212 are due to Sr-2116 impurities.