Giant magnetoresistance effect in granular-type Co-Ag/Ag multilayers

For the granular type of Co-Ag (1.8 nm)/Ag multilayers with the Co contents of 22, 45, and 65 at%, the magneto-resistance ratio ((Delta) R/R) has a maximum found with respect to the AG spacer layer thickness. It is found that with increasing Co content the (Delta) R/R peak shifts towards thicker AG layers. For the Co-Ag/Ag multilayers with low Co contents, (Delta) R/R increases monotonically with increasing magnetic layer thickness, but has a maximum near the magnetic layer thickness of 2.2 nm for the sample having a higher Co content. The peak is thought as a result of the antiferromagnetic (AFM) coupling between the nearest Co clusters in neighboring magnetic layers. In the high field region, the magnetization and the square root of (Delta) R/R vary as a linear function of the reciprocal applied field for all multilayers. In the low field range, they are proportional to the applied field for samples with thin magnetic layers.