Comparative GMR study of Fe/Cu granular films deposited by co-evaporation and cluster beam techniques

We produced Fe/Cu thin films by co-evaporation and cluster-beam (CB) deposition, and compared their magnetoresistance (MR) and magnetic properties. Both co-evaporated and CB-deposited films exhibit giant magnetoresistance (GMR), which do not saturate even at high fields: conduction electrons suffer spin-disorder scattering. With increasing Fe concentration, MR of the co-evaporated films show a sharp maximum at around 23 at.% Fe owing to percolation of magnetic Fe atoms. MR of the CB-deposited films, on the other hand, does not show such a peak. The magnetization of co-evaporated films is smaller than that of CB-deposited films and they do not saturate easily. These observations suggests that the magnetic states of the former are spin glass, while the latter may contain small ferromagnetic clusters. These results demonstrate that the co-evaporated films are chemically and magnetically homogeneous, whereas the CB-deposited films are heterogeneous having granular natures.