Influence of the thickness of the CoFe layer on the negative spin-valve effect in CoFe/Ag/CoFeGd trilayers

Abstract A negative spin-valve effect has been previously observed in a CoFe/Ag/amorphous (CoFe)Gd trilayer. It was attributed to the scattering of the conduction electrons of the Ag layer by only the Co or Fe moments of both magnetic layers. We investigate here the effect of the thickness of the CoFe magnetic layer. Using atomic force microscopy, we show that increasing the thickness of the CoFe layer does not change significantly the roughness of the CoFe/Ag interface. This increase nevertheless modifies the relative weight of the negative spin-valve effect occurring in the vicinity of the interfaces and of the anisotropic magnetoresistance effect occurring within the transition metal layer. The spin-valve effect can be amplified by the insertion of a thin CoFe layer between the Ag and (CoFe)Gd layers.