Giant Magnetoresistance of Co－SiO2 Nano－Granular Films

The heterogeneous Co\- x (SiO\-2) 1-x thin granular films have been fabricated on glass substrates by the ion\|beam co\|sputtering technique at different temperatures.The films with 200?nm thickness consist of granules (cobalt) embedded in nonmagnetic matrix (SiO\-2).A giant magnetoresistance (GMR) ratio of about 4% at room temperature has been observed for x =35% (volume fraction).The GMR ratio of samples decreased while increasing the substrate temperature ( T s).By studying the V\|I curve and ρ T curve of the Co 35 (SiO\-2) 65 sample,we conclude that besides the spin\|dependant tunneling,there may exist another mechanism resulting in the GMR effect of the ferromagnet\|insulator nano\|granular film,which needs further study.