Room-temperature ferromagnetism in Si-SiO2 composite film on glass substrate

Room-temperature ferromagnetism (FM) has been observed in Si-SiO2 amorphous films grown on glass substrates. The magnetic moment was largest in the case of the Si-SiO2 thin film with a Si volume percentage of 16 vol%. The Si content also impacts the magnetic order of the film, and distinct domains were detected in our films. The delicate difference in the M (H) curve between the cases where thermal annealing was carried out in O2 and Ar atmosphere indicates that the observed ferromagnetism does not originate primarily with oxygen defects. It was concluded that the ferromagnetism arose due to direct coupling between defects. These defects come from the interface between the Si particles and the SiO2 matrix. By tuning the Si content in the thin films, one can change the defect density and thereby control the strength of the ferromagnetic coupling.