Giant Magnetoresistance of Fe/Ag Multilayer Films with Ultrathin Fe Layers

A giant magnetoresistive effect in as-deposited Fe/Ag multilayer films with ultrathin Fe layers has been observed.The magnetoresistance in this system is presented first as a function of Fe layer thickness tFe.The sample with Fe layer thickness of 4Åexhibits a magnetoresistance ratio as large as 14.3%at 4.2K.The magnetoresistance ratio decreases approximately an order of magnitude with increasing tFe from 4 to 10Åand then changes slightly with further increasing tFe.From the hysteresis loop measurement,it is found that the interlayer coupling changes from antiferromagnetic to ferromagnetic with increasing tFe.The feature of material at the interface might be responsible for all these findings.