Giant magnetoresistance of Co-SiO2 nano-granular films

The heterogeneous Co-x (SiO2)(1-x), thin granular films have been fabricate d on glass substrates by the ion-beam cosputtering technique at different t emperatures. The films with 200 run thickness consist of granules (cobalt) embedded in nonmagnetic matrix (SiO2). A giant magnetoresistance (:GMR) rat io of about 4% at room temperature has been observed for x = 35% (volume fr action). The GMR ratio of samples decreased while increasing the substrate temperature (T-s). By studying the V-I curve and rho-T curve of the Co-35(S iO2)(65) sample, we conclude that besides the spin-dependant tunneling, the re may exist another mechanism resulting in the GMR effect of the ferromagn et-insulator nano-granular film, which needs further study.