The effect of Co ion implantation on Ge1−xMnx films

► In this paper, Ge1−xMnx (x = 0, 0.013, 0.0226, 0.0339, 0.0565, 0.0678, 0.0904, 0.113) films prepared by magnetron sputtering at 773 K had a Ge cubic structure except for x = 0.1130. ► Co ion implantation into these films can effectively prevent the formation of a second phase. ► Different from the previous reports, both single-doped and co-doped samples were ferromagnetic at room temperature. ► The results show that the room-temperature ferromagnetism is intrinsic property.