The occurrence of intrinsic ferromagnetism in energetic ion irradiated fullerene films is reported. The magnetic properties of irradiated fullerene films are studied by superconducting quantum interference device and electron spin resonance. Raman spectroscopy measurement has been performed to investigate the structural transformation at high fluence. The role of electronic energy density deposition by the ions on their magnetic properties is investigated. The origin of magnetic signal in irradiated films is due to the generation of an amorphous carbon network consisting sp(2)/sp(3) bonded carbon atoms. (C) 2008 The Japan Society of Applied Physics