  Amorphous silicon-nitrogen thin films doped with rare-earth elements
(a-SiN:RE; RE = Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb, and Lu) have been
prepared by co-sputtering and studied by means of electron spin resonance
(ESR). It was found that the neutral dangling-bond density [D0] of a-SiN films
decreases with the presence of magnetic REs and the drop of [D0] approximately
scales with the spin and/or the de Gennes factor of each rare-earth element.
These results suggest that a strong exchange-like interaction,
H=J(RE-D0)S(RE).S(D0), between the spin of the magnetic REs and D0 may be
responsible for this behaviour, similarly to the decrease of Tc in RE-doped
superconductors.
