Amorphous silicon-nitrogen (a-SiN) thin films doped with rare-earth elements (RE = Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb, and Lu) were prepared by cosputtering and studied by means of electron spin resonance. It was found that the neutral dangling bond density, [D-0], of the a-SiN films decreases with the presence of magnetic REs and the drop in [D-0] approximately scales with the de Gennes and/or the spin factor of each RE element. Similar to the decrease in T-c in RE-doped superconductors, our experimental results strongly suggest that an exchange-like interaction, H similar to J(RE.D0)S(RE).S-D0, between the spin of the magnetic REs and that of the D-0 is taking place. (C) 2003 Published by Elsevier Ltd.128417004750