Amorphous silicon films doped with Y, La, Gd, Er, and Lu rare-earth elements (a-Si:RE) have been prepared by cosputtering and studied by means of electron-spin resonance (ESR) and dc magnetization. For comparison purposes the magnetic properties of laser-crystallized and hydrogenated a-Si:RE films were also studied. It was found that the rare-earth species are incorporated in the a-Si:RE films in the RE3+ form and that the RE doping depletes the neutral dangling bond (D-0) density. The reduction of D-0 density is significantly larger for the magnetic RE's (Gd3+ and Er3+) than for the nonmagnetic ones (Y3+, La3+, Lu3+). These results are interpreted in terms of an exchangelike interaction H(int)similar to-J(RE-DB)S(RE)S(DB) between the spin of the magnetic RE's and that of the D-0. All our Gd-doped Si films showed basically the same broad ESR Gd3+ resonance (DeltaH(pp)approximate to850 Oe) at gapproximate to2.01, suggesting the formation of a rather stable RE-Si complex in these films.6817