Effect of metallic Al cap layer on the interlayer coupling in nano-oxide added spin valves

A detailed work on the enhancement of the interlayer exchange coupling (IEC) in the nano-oxide added spin valves when metallic Al is used as the cap layer is presented. The interlayer coupling field and MR ratio as a function of the thickness of the Al was measured for two series of spin valves with the structures of Ta/NiFe/IrMn/CoFe/Ru/CoFe/CoFe/Cu/CoFe/Al/AlO and Ta/NiFe/IrMn/CoFe/Ru/CoFe/Cu/CoFe/Al/AlO. It is concluded that huge enhancement of the interlayer coupling observed in nano-oxide added spin valves is ascribed to the quantum size effect caused by the non-oxidized metallic Al layer between the free layer and AlO cap layer.