Giant magnetoresistance properties in granular type (Co-Ag)/Ag multilayers

The giant magnetoresistance of sputtered granular type (Co-Ag)/Ag multilayers with different Co content and sublayer thickness' was studied. With an increasing Ag layer thickness, the magnetoresistance ratio Delta R/R first increases to reach a maximum and then decreases. With an increasing Co content in the magnetic layers, the maximum shifts towards a large Ag layer thickness. These phenomena can be attributed to the antiferromagnetic coupling between the Co clusters in neighboring Co-Ag layers. With an increasing Co-Ag layer thickness, Delta R/R increases monotonically for a small Co content in the magnetic layers, while for a large Co content, a maximum appears at a small magnetic layer thickness. It is suggested that the interplay of spin dependent scattering and the shunting effect in the Co-Ag layers results in the above thickness dependence. (C) 1998 American Institute of Physics. [S0021-8979(98)03402-1].