High frequency electron spin resonance in Er_m@C_2n

High-field electron spin resonance experiments have been performed on an Er fullerene extract, containing about 1% endohedral Er fullerenes (Erm@C82). The ESR spectra of (Erm@C82) show two resonances, which we propose to originate from the (Er@C82) molecules, one resonance from an unpaired electron on the fullerene cage and one from the Er3+ 4f electrons. © 1995.