Tunable room temperature ferromagnetism in fullerene thin film induced by 1 MeV proton microbeam irradiation

Abstract

We report tunable ferromagnetic properties of thin films of fullerene upon 1 MeV proton microbeam ion irradiation, by varying the ion fluence. Focused microbeam scanning of 1 MeV proton ions have been performed on the fullerene thin films. Consequently, a stable and significant ferromagnetic ordering at room temperature has been observed in the fullerene thin films. The proton microbeam irradiation induces a maximum magnetic ordering in fullerene with optimum dosage and subsequently higher fluence irradiations yield, diminishing effect upon the observed ferromagnetic ordering due to the higher degree of damages. The X-ray diffraction and Raman analysis confirm the damage due to proton microbeam irradiation. The reduction in the saturation magnetic moment induced, is very sharp as a result of exposure to the larger ion fluence. The approximate distance between defects has been simulated computationally, and its relation with observed ferromagnetism has been established. The irradiation has been performed at moderate ion flux (low microbeam current) to avoid the possible annealing effects of the ion irradiation.