Effect of sputtering condition and heat treatment in Co/Cu/Co/FeMn spin valve

The exchange field of Cu(50 A˚)/FeMn(50 A˚)/Co(50 A˚) sputtered on Si substrate was studied in terms of surface roughness and phase formation of γ-FeMn under a variety of Ar pressures and powers in sputtering. It was found that the exchange field is stronger when the surface is smoother and the FeMn layer forms better. The exchange bias field increased by more than three times after heat treatment. The effect of heat treament on magnetoresistance (MR) and resistance of the top spin valve, substrate/Co(30 A˚)/Cu(30 A˚)/Co(30 A˚)/FeMn(150 A˚), was studied. It was observed that the MR started to increase with annealing temperature and the effect was significant at 150°C. The heat treatment led to the disappearance of the intermixed layer between Co and Cu, and the concentration profile of Cu became flat and smooth at this temperature. [Copyright &y& Elsevier]