Spin valves exchange biased by IrMn/PtMn laminated antiferromagnets

This investigation has examined the use of the laminated antiferromagnet PtMn/IrMn to exchange bias spin valves in an attempt to combine the high exchange field and blocking temperature of PtMn with the good pinning profile of IrMn. The effect of varying the IrMn thickness was examined for top and bottom spin values exchange biased by CoFe20 Angstrom/IrMn/PtMn. For top spin valves, H-ex rapidly decreases as IrMn thickness is increased, with the exchange pinning virtually disappearing by 20 Angstrom. As the thickness continues to increase the pinning reappears, and by 40 Angstrom of IrMn an exchange field of 500 Oe and coercivity of 100 Oe are observed. This exchange field is slightly higher than that observed for CoFe/IrMn40 spin valves (400 Oe as deposited, 470 Oe after annealing). For bottom spin valves the same trends are observed, although the pinning never completely disappears. Also, the exchange field of 600 Oe is lower than that obtained for IrMn (670 Oe), presumably due to the rougher interface of the PtMn underlayer. For both top and bottom spin valves the laminated antiferromagnet showed improvement in thermal stability compared to as deposited and annealed IrMn spin valves. (C) 2000 American Institute of Physics. [S0021-8979(00)60208-6].