Effect of Cu layer thickness on giant magnetoresistance properties of NiCoFe/Cu/NiCoFe sandwich

The NiCoFe/Cu/NiCoFe sandwiches were grown onto Si (111) substrate by dc-opposed target magnetron sputtering (dc-OTMS) technique. The growth parameters are: temperature 100degC, applied voltage 600 volt, flow rate of Ar gas 100 sccm, and growth pressure 5.2 times 10^-1 Torr. The effects of Cu layer thickness on giant magnetoresistance (GMR) property of NiCoFe/Cu/NiCoFe sandwich were studied. We have found that the giant magnetoresistance (GMR) ratio is varied depend on the non-magnetic (Cu) layer thickness. The variation of Cu layer thickness of NiCoFe/Cu/NiCoFe sandwich presents an oscillatory behavior of GMR ratio. This oscillation reflects the exchange coupling oscillations between ferromagnetic and antiferromagnetic states, which are caused by an oscillation in the sign of the interlayer exchange coupling between ferromagnetic layers.